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Unmanned Spaceflight.com _ Spirit _ Wheel Trouble

Posted by: mars_armer Mar 14 2006, 12:29 AM

I hate to be the bearer of bad news, but I just heard that there is a serious problem with Spirit's right front drive actuator after yestersol's drive. (This is the actuator that had high currents in the past and led to the backward-driving strategy.) It will take awhile to evaluate the situation, but early speculation is grim.

In a worst-case scenario, they can still drag the bum wheel along, but don't expect another summit view.

Best-case scenario would be a rock or debris jammed in the wheel.

This is a heads-up, sorry I can't really give more info at this time. I still thought you all would like to know.

Posted by: Myran Mar 14 2006, 12:44 AM

Thank you for the heads up mars_armer.
With winter approaching which would mean lower temperatures, something might have jammed, but just as you say, lets hope its just a splinter of rock that can be wiggled loose.

Posted by: DFinfrock Mar 14 2006, 01:20 AM

QUOTE (mars_armer @ Mar 14 2006, 12:29 AM) *
It will take awhile to evaluate the situation, but early speculation is grim.


The problem is, they can't spend a month trouble-shooting like they did with Oppy at Olympia. Spirit has to make progress toward McCool Hill, and that winter haven. sad.gif

David

Posted by: Sunspot Mar 14 2006, 01:27 AM

You mean the wheel will no longer turn at all anymore?

Posted by: Shaka Mar 14 2006, 01:31 AM

QUOTE (mars_armer @ Mar 13 2006, 02:29 PM) *
I hate to be the bearer of bad news,

daaaaaaaaaaammmmmmmmm sad.gif Thanx, Mars. I'd shoot you but I'm too depressed.
Finger crossing time, Guys! You know it has to happen, but still...

Posted by: mars_armer Mar 14 2006, 01:44 AM

QUOTE (Sunspot @ Mar 13 2006, 05:27 PM) *
You mean the wheel will no longer turn at all anymore?

That's right, it stalled. So far the data is limited, so I may be jumping to conclusions. But based on what I've heard, the most likely interpretation is a failed motor, meaning the right front wheel would be steerable but wouldn't turn.

Posted by: Jeff7 Mar 14 2006, 03:28 AM

Yeah, let's really just hope that it's just a rock stuck somewhere. I think something like that happened before.
Either way, they know how to drive the thing in 5-wheel mode, which is good. So spin-round, get to safe ground, then analyze the thing thoroughly.

Posted by: BruceMoomaw Mar 14 2006, 04:13 AM

Do you mean that the wheel won't turn even if its motor drive is disengaged, or just that the motor has failed?

Posted by: Shaka Mar 14 2006, 05:15 AM

QUOTE (BruceMoomaw @ Mar 13 2006, 06:13 PM) *
Do you mean that the wheel won't turn even if its motor drive is disengaged, or just that the motor has failed?

Do we have six clutches on this thing? Can we disengage the motor and free-wheel? huh.gif

Posted by: BruceMoomaw Mar 14 2006, 05:17 AM

Under ordinary circumstances that is possible. In fact, it's what they did when they had the earlier problem with high friction in one of the wheel drives, until they managed to redistribute the lubrication to get the motor working properly again.

Posted by: CosmicRocker Mar 14 2006, 07:08 AM

Oh, no. So that is one reason why Spirit has moved so little recently. It would seem to be an appropriate time to pray to the engineers. It's not likely to be caused by a rock lodged in the wheel, since Spirit has been travelling over a fairly hard surface recently, and the few available hazcams show no suggestion that debris is in the wheel. It is curious though, that there are so few recent hazcams available if there is an issue with that wheel...3 pairs from sol 774, 1 pair from 776, and nothing else so far. Is that due to the MRO/MOI communication? I thought that would be finished by now.

But yes, that seems to be the $64,000 question. Can it still free-wheel as it once did, or is it locked? All I can tell from the images available so far is that Spirit was driving backwards on sol 774 and it left differently appearing left/right tracks. At some point it had turned around 180 degrees, and then it turned back and was in a somewhat different orientatation/location by sol 776.

Even if the wheel is shot, they should be able to drag it to safer ground, but it may take some learning along the way.

Posted by: djellison Mar 14 2006, 08:25 AM

QUOTE (CosmicRocker @ Mar 14 2006, 07:08 AM) *
Oh, no. So that is one reason why Spirit has moved so little recently.


No - read the first post - this is a brand new thing - literally yestersol.

The comparatively little movement recently has been because of the DSN conflict between Spirit and MRO so all commands for Spirit have had to go up via UHF which has a very long lead time - it's like super-restricted sols.

Tosol looks like diag.
QUOTE
780 p0781.03 2 0 0 2 0 4 navcam_1x1_az_324_3_bpp
780 p0981.03 2 0 0 2 0 4 navcam_1x1_az_324_3_bpp
780 p1213.00 2 0 0 2 0 4 ultimate_front_hazcam_3_bpp_pri15
780 p1242.01 1 1 0 0 0 2 front_haz_front_right_wheel_subframe_pri_17
780 p1313.02 2 0 0 2 0 4 rear_haz_ultimate_3bpp_pri15
780 p2138.04 2 0 0 2 1 5 pancam_right_wheel_L27
780 p2138.04 2 0 0 2 1 5 pancam_right_wheel_L27
780 p2600.07 2 2 0 0 2 6 pancam_tau
780 p2630.03 56 2 0 0 2 60 pancam_saw_skysurvey_L4578R2478
781 p1585.00 4 0 4 0 0 8 navcam_cloud_4x1_dwnsmp_RVRAz_calstart

Doug

Posted by: Bill Harris Mar 14 2006, 08:34 AM

Oh well, stuff happens. We're all a lot creakier than we were 30-40 years ago.

My suspicion would be that this is a geartrain failure. I forget the exact reduction ratio, but there many gears and bearings between the motor and the wheel and there has been a failure along the way. Remember, we are many hours past the design service life.

Spirit needs to get to an interesting north-facing site. She may be a 3-legged dog, but we still love her...

--Bill

Posted by: edstrick Mar 14 2006, 10:37 AM

I note that both from Husband hill and from the drive to and around home plate, the driving on the north McCool "flats" and the lower flank of the hill look mostly pretty easy.... likely sand traps are rare and high-density large cobble areas are scarce. Some of that "diagonal" stripe of lighter and grayer colored terrain on McCool are pretty rubbly and cobbly, but they're not in the drive to get onto the hillslope.

Posted by: Marz Mar 14 2006, 03:43 PM

Poor Spirit, just as she regains the lead in milage, she hits another bump in the road.

I suppose there is a plan to return to Homeplate in spring, so I expect the driving around McCool will be very conservative. Maybe if we're lucky, some of the Homeplate unit will be found along the east slopes of McCool.

I was half hoping we could get some closer images of the Chaos terrain that was next on the adjenda, but now I worry it's a rockbed too far.

Posted by: mars_armer Mar 14 2006, 04:37 PM

QUOTE (Shaka @ Mar 13 2006, 09:15 PM) *
Do we have six clutches on this thing? Can we disengage the motor and free-wheel? huh.gif

The short answer: I'm 99% sure the answer is "no".

The long answer: There are two things that resist turning of the wheel when the motor isn't energized: dynamic braking and static detents. Dynamic braking occurs from back-emf in the motor electrical circuit, and provides a resistive torque when the wheel is turned but no force when the wheel is stopped. Dynamic braking can be disengaged in the electrical system. The static detents, on the other hand, are magnets that cause the motor to preferentially stay at certain turn positions. These are necessary to keep the wheels from rolling after the rover comes to a stop, and cannot be disengaged. Because of the high gear ratio of the drive gearbox, it takes a hefty torque to the wheel from the outside to overcome the detent.

Bottom line: assuming the motor stall can't be corrected, they will probably have to drive backwards dragging a stuck RF wheel. This is something they have http://marsrovers.jpl.nasa.gov/gallery/all/2/n/313/2N154158930EFF9300P0745L0M1.JPG in the West Spur area when they were afraid the RF motor was nearing end of life. Though at that time, I think they periodically turned the RF wheel a bit to drive over the buildup of dirt in front of the wheel.

Posted by: tty Mar 14 2006, 05:53 PM

Design lesson for future rovers: there should be some simple and reliable mechanism for unclutching a wheel once it is certain that it is inoperable and cannot be recovered. Some kind of pyro mechanism perhaps?

tty

Posted by: Bill Harris Mar 14 2006, 06:09 PM

QUOTE
there should be some simple and reliable mechanism for unclutching a wheel...

Probably not do-able within the constraints of 'simple and reliable'. Given that the original service life of the Rovers was 90 days and they have lasted a long time, the optimum solution would be to upgrade the motor and geartrain to give a much much longer service life.

--Bill

Posted by: alan Mar 14 2006, 07:49 PM

Something in there?


Posted by: Toma B Mar 14 2006, 08:23 PM

That's good news...if it got in, it can posibly get out of there...Would not be the first time.

Posted by: helvick Mar 14 2006, 08:32 PM

[quote name='alan' post='45573' date='Mar 14 2006, 07:49 PM']
Something in there?
[/quote]
Looks like a rock stuck in there to me. With some stretching and bending of the luminosity curves there seems to be a fairly irregular potato shaped object jammed in there.

If it is a rock is there any chance that it could be jolted loose with some creative driving?

B)-->

QUOTE(Toma B @ Mar 14 2006, 08:23 PM) *

That's good news...if it got in, it can posibly get out of there...Would not be the first time.
[/quote]

The last one that I recall was
http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20041227a/mera-sol345-rhaz-2-A350R1_br.jpg

Posted by: mars_armer Mar 14 2006, 09:34 PM

QUOTE (alan @ Mar 14 2006, 11:49 AM) *
Something in there?

That's really encouraging!

Now I think (hope) I overreacted to the initial description I heard of the problem. At that time it sounded like there was evidence in the telemetry that the motor circuit had failed "open", which suggested a broken wire or brush inside the motor. By comparison, unsticking a rock sounds easy.

I knew I should keep my virtual mouth shut and wait for more data. unsure.gif

Posted by: helvick Mar 14 2006, 09:46 PM

QUOTE (mars_armer @ Mar 14 2006, 09:34 PM) *
I knew I should keep my virtual mouth shut and wait for more data. unsure.gif

Absolutely not ! If everyone waited until they were certain of what they were saying then we'd have nothing to do here.

Posted by: Shaka Mar 14 2006, 09:46 PM

QUOTE (mars_armer @ Mar 14 2006, 11:34 AM) *
That's really encouraging!

Now I think (hope) I overreacted to the initial description I heard of the problem. At that time it sounded like there was evidence in the telemetry that the motor circuit had failed "open", which suggested a broken wire or brush inside the motor. By comparison, unsticking a rock sounds easy.

I knew I should keep my virtual mouth shut and wait for more data. unsure.gif

I hope that's a rock too, but none of it is out in the light looking clearly 'rocky'. I hate to suggest it might just be some internal reflection - like my...er...flying saucer. blink.gif

Posted by: helvick Mar 14 2006, 10:05 PM

QUOTE (helvick @ Mar 14 2006, 09:46 PM) *
Absolutely not ! If everyone waited until they were certain of what they were saying then we'd have nothing to do here.

And just in case we get too optimistic:
http://marsrovers.jpl.nasa.gov/gallery/all/2/f/047/2F130531955ESF0933R2500R0M1.JPG
http://marsrovers.jpl.nasa.gov/gallery/all/2/f/424/2F164010533EFFA8B3P1214R0M1.JPG

There's shading in both of these in exactly the same place and the lighting is from a similar direction.

Posted by: Shaka Mar 14 2006, 10:34 PM

QUOTE (helvick @ Mar 14 2006, 12:05 PM) *
And just in case we get too optimistic:
http://marsrovers.jpl.nasa.gov/gallery/all/2/f/047/2F130531955ESF0933R2500R0M1.JPG
http://marsrovers.jpl.nasa.gov/gallery/all/2/f/424/2F164010533EFFA8B3P1214R0M1.JPG

There's shading in both of these in exactly the same place and the lighting is from a similar direction.

...And the pendulum swings... http://static.flickr.com/36/112580016_7b9d7405a1_o.jpg
Somebody in another forum doing some more intensive photoenhancement.
(Like looking for WMDs)

Posted by: helvick Mar 14 2006, 10:37 PM

QUOTE (Shaka @ Mar 14 2006, 10:34 PM) *
...And the pendulum swings... (Like looking for WMDs)

And finding just dust it would seem. Well time to wait for more news.

Posted by: Sunspot Mar 14 2006, 10:55 PM

I thought it might have been a rock at first... but now i'm thinking it is probably some internal reflection too sad.gif

Posted by: djellison Mar 14 2006, 11:05 PM

At a first look - it just looks like dust to me - and the two sets of diagnostic images ( one presumes before and after a commanded rotation of the wheel ) show no change in the position of the wheel

Doug

Posted by: Bob Shaw Mar 14 2006, 11:06 PM

QUOTE (tty @ Mar 14 2006, 05:53 PM) *
Design lesson for future rovers: there should be some simple and reliable mechanism for unclutching a wheel once it is certain that it is inoperable and cannot be recovered. Some kind of pyro mechanism perhaps?

tty


That's *exactly* how the wheels were organised on the Lunokhods - individual motors which could be popped to allow the wheels to rotate freely if required.

Perhaps old lessons should be *remembered*...

Bob Shaw

Posted by: Daba Mar 14 2006, 11:28 PM

QUOTE (helvick @ Mar 14 2006, 11:05 PM) *
And just in case we get too optimistic:
http://marsrovers.jpl.nasa.gov/gallery/all/2/f/047/2F130531955ESF0933R2500R0M1.JPG
http://marsrovers.jpl.nasa.gov/gallery/all/2/f/424/2F164010533EFFA8B3P1214R0M1.JPG

There's shading in both of these in exactly the same place and the lighting is from a similar direction.


sad.gif It looks like no rock to me. sad.gif sad.gif

Daba

 

Posted by: slinted Mar 14 2006, 11:39 PM

There was a tiny bit of motion between sol 779 and 780, though I'm not sure it is very promising.

http://www.lyle.org/~markoff/collections/spirit_fhaz_sol779_780.gif
click through for a larger (2x) enlargement of the FHAZ images.

The wheel doesn't rotate, and it doesn't change its pointing (steering motor), but it does seem to roll with regard to the suspension which doesn't move. Is that even a commandable motion? We know the wheels can turn and can be pointed (yaw) but can they be rolled?

Posted by: djellison Mar 15 2006, 12:11 AM

That's a very odd motion - at first I thought it might just be a change in lighting, but it's genuine movement.

I've got to give a talk to some students tomorrow that will end with "and here's Spirit's wheel appearing to start falling off"
Doug

Posted by: RNeuhaus Mar 15 2006, 12:49 AM

QUOTE (mars_armer @ Mar 14 2006, 11:37 AM) *
The short answer: I'm 99% sure the answer is "no".

The long answer: There are two things that resist turning of the wheel when the motor isn't energized: dynamic braking and static detents. Dynamic braking occurs from back-emf in the motor electrical circuit, and provides a resistive torque when the wheel is turned but no force when the wheel is stopped. Dynamic braking can be disengaged in the electrical system. The static detents, on the other hand, are magnets that cause the motor to preferentially stay at certain turn positions. These are necessary to keep the wheels from rolling after the rover comes to a stop, and cannot be disengaged. Because of the high gear ratio of the drive gearbox, it takes a hefty torque to the wheel from the outside to overcome the detent.

Bottom line: assuming the motor stall can't be corrected, they will probably have to drive backwards dragging a stuck RF wheel. This is something they have http://marsrovers.jpl.nasa.gov/gallery/all/2/n/313/2N154158930EFF9300P0745L0M1.JPG in the West Spur area when they were afraid the RF motor was nearing end of life. Though at that time, I think they periodically turned the RF wheel a bit to drive over the buildup of dirt in front of the wheel.

Would you post the rover wheel in graphical description? I still have no a good idea about its design. By now, I tought that there are four motors for motion: 2 in front and 2 in back and the motor axis is connected to the wheel. The others motor are for turning control which are connected at the top of every four motors: 2 front and 2 back. Isn't that correct?

P.D. If that looks so, I think that design is the most elegant but not the most robust. Hope this would provide a good lesson for the next Mars rover : MSL (I am afraid that its wheel design is very similar to MER according to the very generic picture.)

Rodolfo

Posted by: RNeuhaus Mar 15 2006, 01:06 AM

QUOTE (tty @ Mar 14 2006, 12:53 PM) *
Design lesson for future rovers: there should be some simple and reliable mechanism for unclutching a wheel once it is certain that it is inoperable and cannot be recovered. Some kind of pyro mechanism perhaps?

tty

Once time, one of the wheels of my truck was stuck by a small stone (between the brake and wheel) and it started to noise awfully. The only way to get rid off the small stone from the wheel was to use a long screwdriver and hammer. What might be done with MER?

As MER goes very slow and I don't think that any small stone would stuck any wheel and the most probably ones would be of dust, grain or sand. The use of any kind of shaking with pyro or anything else is not a good design. The best ones would be the wheels have a very tight seal that neither a water or powder can filter into it.

On the other hand, the rover wheel has smaller circunference and its 5 kilometers is like 1,000 km for a off road truck with its big tires (I don't exactly compare the cicunference distance). After that distance, a truck need a chasis wash to flush off the dust and other dirty things and some lubrications in their joints. The MER ones has no such service for more than two years. That is Amen!

Rodolfo

Posted by: ElkGroveDan Mar 15 2006, 01:24 AM

QUOTE (slinted @ Mar 14 2006, 11:39 PM) *
The wheel doesn't rotate, and it doesn't change its pointing (steering motor), but it does seem to roll with regard to the suspension which doesn't move.


Interesting. That could be a good sign. It looks like it's torquing against a load, causing the suspension to shift, which would infer something jammed somewhere out of view. That would be a far better situation than a malfunctioning motor.

Posted by: Bill Harris Mar 15 2006, 04:01 AM

Not at all good. Slinted's animated-GIF shows that there is radial motion of the wheel, which suggests to me that a wheel bearing has failed.

--Bill

Posted by: mars_armer Mar 15 2006, 04:33 AM

Looks like a drive will be attempted on Sol 781 (dragging the right front wheel), after some diagnostics. Goal is to move toward an area ~14m away with a more favorable power situation.

There is no debris in the wheel, but also no explanation yet for the anomaly.

Posted by: monty python Mar 15 2006, 09:49 AM

QUOTE (tty @ Mar 14 2006, 11:53 AM) *
Design lesson for future rovers: there should be some simple and reliable mechanism for unclutching a wheel once it is certain that it is inoperable and cannot be recovered. Some kind of pyro mechanism perhaps?

tty

In a future mission, how about just blowing off the whole wheel? Pyro wouldn't add much weight.

Posted by: Ames Mar 15 2006, 10:47 AM

QUOTE (monty python @ Mar 15 2006, 09:49 AM) *
In a future mission, how about just blowing off the whole wheel? Pyro wouldn't add much weight.


Cheers Monty

Now that has my warped sense of humour going huh.gif

Couldn't have come from a better named contributor laugh.gif

But seriously, that is a good point - if a stuck wheel is an impediment - chop it off!

Nick

Posted by: edstrick Mar 15 2006, 10:49 AM

quote: "I've got a little list..... I'm SURE it won't be missed!"

Posted by: Burmese Mar 15 2006, 01:57 PM

Yeah, wheel bearing looks likely to me, or some other 'broken' component besides a motor winding. Does anyone know if the wheels have -any- free movement in a radial direction under normal circumstances?

Posted by: odave Mar 15 2006, 02:16 PM

QUOTE (Ames @ Mar 15 2006, 05:47 AM) *
But seriously, that is a good point - if a stuck wheel is an impediment - chop it off!


It's just a flesh wound! smile.gif

However, I think we'd run into some problems with balance and stability if a wheel gets blown off. Not so bad on the flats, but I think Spirit would lose her mountain goat abilities.

Posted by: MahFL Mar 15 2006, 06:10 PM

Strange co-incidence......today the front left wheel bearing went kaput on our van, its fixed now though smile.gif

Posted by: djellison Mar 15 2006, 06:48 PM

I gave a talk to some 16-18 y.o. school students today - and I always finish my talks with the most recent image I can get before the talk starts...so today I finished talking about Spirit thus...

"To bring it bang up to date, this image was taken yesterday morning, and shows the front right wheel - the same one that was a temporary problem 600 sols ago, essentially stuck. A major stall of the motor suggest that something might be broken for good inside the mechanics of the wheel - so I'm sad to say that I leave Spirit with the news that yes, one of its wheels might be about to fall off"

For a bunch of typical teenagers, they got most of the space related gags, went oOoo at the right anaglyphs, wow at the right pictures - and indeed laughed at the idea of a dodgy wheel falling off. For the Brits ammoungst you, there's a joke about finding a Mars rover up on bricks with 6 missing wheels somewhere in there, with the mission engineers saying something like "I KNEW we shouldnt have had that engineering consultant from Liverpool in to do the job"


Doug

Posted by: lyford Mar 15 2006, 07:35 PM

QUOTE (monty python @ Mar 15 2006, 01:49 AM) *
In a future mission, how about just blowing off the whole wheel? Pyro wouldn't add much weight.

well, maybe just to blow open the clutch or something so it could freely turn - then dragging it wouldn't be dead weight.

Posted by: Sunspot Mar 15 2006, 07:54 PM

Still limping along:

http://qt.exploratorium.edu/mars/spirit/forward_hazcam/2006-03-15/2F195702005EFFAQ23P1210R0M1.JPG

Posted by: Burmese Mar 15 2006, 08:05 PM

Good, they aren't going to sit still and spend a week analyzing the problem w/o moving. I suspect they just make best time possible to the slopes and then take a breather to see if they can do anything about it.

No updates from SS since Feb 5th, really could use another one by now.

Posted by: general Mar 15 2006, 08:13 PM

QUOTE (Sunspot @ Mar 15 2006, 08:54 PM) *
Still limping along:

http://qt.exploratorium.edu/mars/spirit/forward_hazcam/2006-03-15/2F195702005EFFAQ23P1210R0M1.JPG



Looks like she's returning to Home Plate

Posted by: Marcel Mar 15 2006, 08:16 PM

QUOTE (Sunspot @ Mar 15 2006, 08:54 PM) *
Still limping along:

http://qt.exploratorium.edu/mars/spirit/forward_hazcam/2006-03-15/2F195702005EFFAQ23P1210R0M1.JPG

Ohmy...this doesn't look good at all. Let us not forget, that dragging a blocked wheel is no problem in this loose material, but roving around rocks is a must in this situation. If it's really stuck (which is most certainly the case because of the high gear ratio indeed), rocks that could be driven over before are an obstacle now: draging along rocks isn't easy on 5 working wheels.

It might get us some interesting views under rocks though....something we did not see before ! I remember thread that was about turning rocks with the arm ! And: we'll get a loooong trench ! ALWAYS look at the bright side of life (I am trying to keep the corners of my mouth up !)

I hope this motor starts working again. I remember something about a gear ratio well within hundreds: this means it is going to be hard to force the motor back and forth by excerting force on the wheel itself. It might be done in combination with a high current boost through the actuator, while pushing the wheel to a stationairy surface (large, coarse rock, with the "cleats" of the wheel pushed on it): the other 5 might slip then.... unsure.gif unsure.gif

Fingers crossed that they'll fix it....like they did before. That wasn't a complete stall however...it was a higher current, but still turning.

Posted by: elakdawalla Mar 15 2006, 08:24 PM

Squyres did not mention the wheel trouble in his talk today about Spirit. In fact he said at the end "Spirit has just completed a drive in the direction of Oberth and Korolev, we hope in a week or so to be on one of those nice toasty slopes that will allow us to survive another winter at Mars."

For what that's worth.

--Emily

Posted by: imipak Mar 15 2006, 08:37 PM

QUOTE (monty python @ Mar 15 2006, 09:49 AM) *
In a future mission, how about just blowing off the whole wheel? Pyro wouldn't add much weight.


Pyros could malfunction, and go off early - or, worse, simultaneously...

Cue bad Micahel Caine impression -- "You're only s'posed to blow the bloody doors off!"

Posted by: Sunspot Mar 15 2006, 08:50 PM

QUOTE (Marcel @ Mar 15 2006, 08:16 PM) *
Ohmy...this doesn't look good at all. Let us not forget, that dragging a blocked wheel is no problem in this loose material, but roving around rocks is a must in this situation.


Maybe they were just testing it with a short drive.... and will try longer ones in the days ahead.

Posted by: centsworth_II Mar 15 2006, 09:01 PM

"Looks like she's returning to Home Plate" -- General
Not if that's Husband Hill in the background.

"(I am trying to keep the corners of my mouth up !)" -- Marcel
If all else fails, try standing on your head. smile.gif

Posted by: Shaka Mar 15 2006, 09:07 PM

QUOTE (elakdawalla @ Mar 15 2006, 10:24 AM) *
Squyres did not mention the wheel trouble in his talk today about Spirit. In fact he said at the end "Spirit has just completed a drive in the direction of Oberth and Korolev, we hope in a week or so to be on one of those nice toasty slopes that will allow us to survive another winter at Mars."

For what that's worth.

--Emily

It's not exactly the kind of note a scientific 'knight in armor' wants to conclude his latest progress report with, Emily. He would say it's too soon to evaluate the problem, so 'not worth mentioning' today. Fair enough, I suppose, but I'll bet he's wishing he'd made an update last week at his Mission to Mars site. Then it could have been entirely upbeat, now...
Obviously, those static detents, Mars_Armer described are doing their job too well, the bad wheel has not budged despite that long drag. sad.gif Marcel may well be right, a protruding bedrock meeting the bad wheel might 'anchor' us fast, forcing a back-up. Might mean trickier drive programming and keeping to the sand where possible. Dam'n'Blast! Time's'a'wastin'! We've got to get North, FAST before we freeze!
Don't know about those pyrotechnic charges, boys. One short-circuit or static discharge might instantly convert us into a stationary 'rover'. Better to equip MSL with a powerful rock-biting sampler that could be programmed to gnaw the leg off. wink.gif

P.S. Emily, do you mind if I ask a personal question? What is your avatar a picture of? I've guessed 'dented daisy', 'tattered tutu', 'mutant ephyra', but I'm still unsure.
Hope the weather's fine in Houston.

Posted by: AlexBlackwell Mar 15 2006, 09:10 PM

QUOTE (Shaka @ Mar 15 2006, 09:07 PM) *
P.S. Emily, do you mind if I ask a personal question? What is your avatar a picture of? I've guessed 'dented daisy', 'tattered tutu', 'mutant ephyra', but I'm still unsure.

It's a radar image of the venusian surface from Magellan.

Posted by: Shaka Mar 15 2006, 09:49 PM

QUOTE (AlexBlackwell @ Mar 15 2006, 11:10 AM) *
It's a radar image of the venusian surface from Magellan.

Awesome, AB. I see the obvious link with Venus,(Men are from Mars...), but what is the actual structure? A volcano or something? Anywhere I can see a blowup of the pic?

Posted by: helvick Mar 15 2006, 09:54 PM

QUOTE (AlexBlackwell @ Mar 15 2006, 09:10 PM) *
It's a radar image of the venusian surface from Magellan.

Lavinia ?
]

Posted by: djellison Mar 15 2006, 10:18 PM

QUOTE (Shaka @ Mar 15 2006, 09:49 PM) *
I see the obvious link with Venus,(Men are from Mars...),


The less obvious (but more accurate) link is that Emily did research on Venus with Magellan data before working at TPS.

Doug

Posted by: odave Mar 15 2006, 10:20 PM

QUOTE (Shaka @ Mar 15 2006, 04:49 PM) *
I see the obvious link with Venus,(Men are from Mars...)


See a http://www.unmannedspaceflight.com/index.php?s=&showtopic=2132&view=findpost&p=38654 from Emily.

Is she busy or something this week? wink.gif

Posted by: Bill Harris Mar 15 2006, 10:23 PM

>Looks like she's returning to Home Plate

And not with Oberth, et al, in the Rear hazcam (forward-facing).

--Bill

Posted by: djellison Mar 15 2006, 10:31 PM

I think they moved to the nearest patch that offered a slightly better tilt w.r.t. solar power for a few days of analysis - toward or away from HP, I doubt they cared much.

Doug

Posted by: alan Mar 15 2006, 10:34 PM

First impression: the right front wheel looks like it is locked.
But if you look at images from last year, you can see that Spirit created trenches when it traversed soft material.
Image from sol 313 for comparison
http://marsrovers.jpl.nasa.gov/gallery/all/2/n/313/2N154158930EFF9300P0745R0M1.JPG
I assume for now that the wheel will turn when it meets enough resistance.

Posted by: Shaka Mar 15 2006, 11:00 PM

QUOTE (odave @ Mar 15 2006, 12:20 PM) *
See a http://www.unmannedspaceflight.com/index.php?s=&showtopic=2132&view=findpost&p=38654 from Emily.

Is she busy or something this week? wink.gif

OH, Maannnnn. huh.gif There is so much I don't know, it's scary!
OK I've never even dropped in at one of the other planets in UMSF. Until it went orbital, I'd never even seen the MRO section! My toolbar button goes straight to MER. The truth is I'm spending too much of my remaining 'fourscore and ten' already on the MER pages! But this is planetary science I can touch. This is almost as good as biology. (I can pay no higher compliment.) When I was an astronomer (age 7 - 10), I would have been able to quote chapter and verse of UMSF from A to Z. Time marches on. sad.gif
Lavinia? Is that the ravishing name of that diaphanous 'flower' at upper left? Are they volcanoes? (I am as a newborn babe on this planet, but, PC be damned, I know a blessedly feminine place when I see it.)
smile.gif

Edit note: Now that I've studied the blowup, I assume they're impact craters. The radar makes the proximal ejecta look like flower petals! Cool.

Posted by: Shaka Mar 15 2006, 11:57 PM

wheel.gif http://static.flickr.com/41/113051772_e40da86735_o.gif
Nice animated anaglyph from the other forum, if you haven't seen it.

Posted by: CosmicRocker Mar 16 2006, 04:10 AM

QUOTE (elakdawalla @ Mar 15 2006, 02:24 PM) *
Squyres did not mention the wheel trouble in his talk today about Spirit. In fact he said at the end "Spirit has just completed a drive in the direction of Oberth and Korolev, we hope in a week or so to be on one of those nice toasty slopes that will allow us to survive another winter at Mars."

For what that's worth.

--Emily
Jim Bell concluded his presentation in the morning session by mentioning that most recently they had taken diagnostic images of the wheel, and that Steve Squyres might have more to say when he speaks. After SS didn't mention it, all ll I could think was that they didn't know enough yet to speculate.

I had a short chat with Matt Golombek after the last presentation. Although I should have known better, I couldn't help but ask him if they had any ideas about the wheel problem. As you might expect, he told me it was too soon to speculate because it was such a recent development. He also said the engineers were investigating (again, something you might suspect). So, I wasn't able to learn anything new, but only confirmed what one would logically suspect.

...for what _that_ is worth.

Posted by: mars_armer Mar 16 2006, 04:44 PM

The wheel is definitely looking dead (open circuit, consistent with a brush failure).

Without giving up on the motor, the most productive engineering effort will probably be enhancing the efficiency of 5-wheel-drive. The sol 781 drive took almost an hour to drive a total of ~4 meters, because of the need for visodom and other extra imagery. Their durrent energy budget only allows 1 to 1.5 hours of driving per day, so this gives you an idea of the pace you can expect.

Another drive is planned on sol 782.

QUOTE (alan @ Mar 15 2006, 02:34 PM) *
I assume for now that the wheel will turn when it meets enough resistance.

My understanding is that it takes ~30 N-m (22 ft-lb) of torque on the wheel to overcome the detent. Good for holding position on slopes, but it now makes it unlikely that the wheel will ever turn again. Deeply embedded rocks could easily snare the RF wheel.

Posted by: Sunspot Mar 16 2006, 05:28 PM

QUOTE (mars_armer @ Mar 16 2006, 04:44 PM) *
Their durrent energy budget only allows 1 to 1.5 hours of driving per day, so this gives you an idea of the pace you can expect.


Oh dear...that's very bad news... Spirit's roving days are pretty much over then.

Posted by: ToSeek Mar 16 2006, 05:48 PM

QUOTE (odave @ Mar 15 2006, 10:20 PM) *
See a http://www.unmannedspaceflight.com/index.php?s=&showtopic=2132&view=findpost&p=38654 from Emily.

Is she busy or something this week? wink.gif


She's at the Lunar and Planetary Science Conference.

Posted by: AlexBlackwell Mar 16 2006, 05:50 PM

QUOTE (ToSeek @ Mar 16 2006, 05:48 PM) *
She's at the Lunar and Planetary Science Conference.

I was wondering where she had disappeared to.

Posted by: ToSeek Mar 16 2006, 05:50 PM

QUOTE (Sunspot @ Mar 16 2006, 05:28 PM) *
Oh dear...that's very bad news... Spirit's roving days are pretty much over then.


Well, until next summer, at least.

Posted by: mars_armer Mar 16 2006, 06:13 PM

> Well, until next summer, at least.

And don't discount their ability to come up with clever driving algorithms, that can improve efficiency without compromising safety.

Posted by: odave Mar 16 2006, 06:17 PM

I'm sure the MER engineers will be able to squeeze more meters out of future 5 wheel drives, so I don't think Spirit will turn into a lander mission just yet. It just looks like I'll have to give up my hope of seeing a pan from Spirit at the mouth of Ma'adim Vallis smile.gif

Posted by: helvick Mar 16 2006, 06:46 PM

QUOTE (odave @ Mar 16 2006, 06:17 PM) *
I'm sure the MER engineers will be able to squeeze more meters out of future 5 wheel drives, so I don't think Spirit will turn into a lander mission just yet. It just looks like I'll have to give up my hope of seeing a pan from Spirit at the mouth of Ma'adim Vallis smile.gif

That may be hoping for too much but I don't think that losing one wheel is catastrophic. The 4m progress rate is more a consequence of the visodm drive mode. In a fully planned or blind drive she should be able to go further if and when the circumstances and terrain allow.

On the plus side the http://www.nature.com/news/2006/060313/full/060313-11.html So the planning is still for the long term.

Posted by: odave Mar 16 2006, 06:55 PM

Yeah, I know that Ma'adim Vallis is not a realistic goal - I've just always fantasized about what a killer desktop image it would make cool.gif

Posted by: Bob Shaw Mar 16 2006, 08:46 PM

QUOTE (helvick @ Mar 16 2006, 06:46 PM) *
On the plus side the http://www.nature.com/news/2006/060313/full/060313-11.html So the planning is still for the long term.


Oh no! Not Vista!

Can Autostitch make Blue Screen Of Death screens into panoramas?

Bob Shaw

Posted by: Marz Mar 16 2006, 09:14 PM

QUOTE (odave @ Mar 16 2006, 12:55 PM) *
Yeah, I know that Ma'adim Vallis is not a realistic goal - I've just always fantasized about what a killer desktop image it would make cool.gif


lol - when you dream, why not dream big!

Let me try some quasi-irrational optimism: is there any possibility that the wheel-freeze is a side-effect of much cooler temperatures? Could warmer summer temperatures suddenly result in a working wheel again?

My kingdom for a well-placed drop of oil! ph34r.gif

Posted by: djellison Mar 16 2006, 10:02 PM

The day time temps might be getting to -60 instead of say, -20 - but it still goes down to lots more than -100 at night. And even then - all the wheels have heaters.

Doug

Posted by: Jeff7 Mar 16 2006, 10:46 PM

Can't they just use the routines they developed before when Spirit's one wheel acted up? I thought that they'd figured out a fairly decent method of compensating for the navigational problems caused by a stuck wheel.

Posted by: djellison Mar 16 2006, 10:50 PM

Spirits wheel wasnt stuck back in the 150-350 sol region.The motor pulled more current when driven, 3x more than the others, and they thought that if it got worse they'd kill the motor - but it DID work when commanded to.

So - they commanded it to not turn about 90% of the time, and just turn it 10% of the time to clear the little trench it was digging.

What we have here is when you command the wheel to turn, it doesnt, a different problem, and possibly not even a related problem to the trouble of 500 sols ago.

Doug

Posted by: Shaka Mar 16 2006, 10:57 PM

QUOTE (Marz @ Mar 16 2006, 11:14 AM) *
lol - when you dream, why not dream big!

Let me try some quasi-irrational optimism: is there any possibility that the wheel-freeze is a side-effect of much cooler temperatures? Could warmer summer temperatures suddenly result in a working wheel again?

My kingdom for a well-placed drop of oil! ph34r.gif

Mars_armer's authoritative report that the motor circuit failed "open" indicates a break in the circuit - a broken wire or a broken motor brush. A technician with a soldering iron might be able to fix it in a jiffy, but we ain't got one unless Marvin the Martian shows up. The motor is not straining against a blockage or frozen bearing - it's lifeless sad.gif

Posted by: GregM Mar 17 2006, 03:22 AM

.

Posted by: ddeerrff Mar 17 2006, 04:29 AM

QUOTE (Shaka @ Mar 16 2006, 04:57 PM) *
Mars_armer's authoritative report that the motor circuit failed "open" indicates a break in the circuit - a broken wire or a broken motor brush. .....


Are the wheel drive motors really DC motors with brushes?!? I would have expected stepping motors.

Posted by: Shaka Mar 17 2006, 04:32 AM

QUOTE (GregM @ Mar 16 2006, 05:22 PM) *
My biggest concern about all of this is that if the Rover cannot climb the hill on 5 wheels, it will not gain enough altitude to catch the wind, and therefore not be able to clean off the solar panel. Even if it gets to the base of the hill and gets on a tilt that alllows better positioning with respect to the sun, it is only buying a little time. Eventually the dust will accumulate on the panel and starve Spirit anyway. Sooner or later it will need wind. The wind is up high on the hill. It needs to be able to climb somehow.

Be brave, Greg! We don't know yet what Spirit can do on 5 wheels. Maybe it will be able to climb McCool, slowly and with frequent roadblocks when the Bad Wheel (TBW) catches on a rock. Then we will have to back up, turn, and go around the rock. It will be slooowwww progress. But we have all the time the gods of space probes have allotted Spirit.
As to catching the wind, we could see a huge improvement as soon as we get into the Pass between McCool and Husband Hills. If you aren't familiar with the wind power they can provide, Google on wind farms, and Tehachapi, San Gorgonio, and Altamont Pass. We don't have to reach the peak of McCool to get the wind. On the contrary, it may be extra strong down in the pass.
To be the final, ultimate, SuperHero of Mars exploration, Spirit needs to slowly climb the north face of McCool Hill. If it gets even half way to the summit, it should have a bronze statue in every city park in America! smile.gif

Posted by: RNeuhaus Mar 17 2006, 06:11 AM

QUOTE (Shaka @ Mar 16 2006, 11:32 PM) *
As to catching the wind, we could see a huge improvement as soon as we get into the Pass between McCool and Husband Hills.

That is true. I have observed it on the Earth experience. The highest point of a valley, goes a strong wind tunneled by the lower valley. Hope that the point of junction of two hills: Husband and McCool there would be windy.

Rodolfo

Posted by: MahFL Mar 17 2006, 03:17 PM

"We're now in a drive or die situation," says Steve Squyres of Cornell University, Ithaca, New York, who leads the rover science team. "Our current focus is to drive like hell and get to a safe winter haven."

I did not realise the situation was that dire...............

Posted by: helvick Mar 17 2006, 04:08 PM

QUOTE (MahFL @ Mar 17 2006, 03:17 PM) *
"We're now in a drive or die situation," says Steve Squyres of Cornell University, Ithaca, New York, who leads the rover science team. "Our current focus is to drive like hell and get to a safe winter haven."

I did not realise the situation was that dire...............

Power is at 350 watt hours per sol now with daily insolation at 3630 whr per m^2. Insolation drops to its winter minimum of 2770 on August 24th (Sol 909). If they do not move and there is no additional dust deposition power would drop to 267 whr by then. Factoring in dust deposition causes an additional 0.08% per sol loss so the power level will probably drop to 241whr. 280whr is the number that we suspect is the minimum survival level, SS has said this in the past. A good slope (15-20% tilt approximately facing the noon sun) would add 20-30% to that bringing Spirit back to a level where she can survive and possibly even do some work.

Posted by: djellison Mar 17 2006, 04:09 PM

<360 Whr's per sol and decreasing quite rapidly

Doug

Posted by: ToSeek Mar 17 2006, 06:23 PM

QUOTE (helvick @ Mar 17 2006, 04:08 PM) *
Power is at 350 watt hours per sol now with daily insolation at 3630 whr per m^2. Insolation drops to its winter minimum of 2770 on August 24th (Sol 909). If they do not move and there is no additional dust deposition power would drop to 267 whr by then. Factoring in dust deposition causes an additional 0.08% per sol loss so the power level will probably drop to 241whr. 280whr is the number that we suspect is the minimum survival level, SS has said this in the past. A good slope (15-20% tilt approximately facing the noon sun) would add 20-30% to that bringing Spirit back to a level where she can survive and possibly even do some work.


Even the extra 20% would make it only up to 290 whr. Sounds like one cloudy day could be the end of Spirit....

Posted by: mars_armer Mar 17 2006, 06:37 PM

How sure are we of the 280 Whr "death" number? It's hard to believe that Spirit couldn't hunker down with overnight deep sleeps and infrequent comm passes and at least survive with much less than that. Could it be that SS was really talking about a minimum power level for usability, rather than a survival limit?

Edit: Plenty of discussion on this subject in http://www.unmannedspaceflight.com/index.php?s=&showtopic=1718. My impression is that we know a lot more about power availability than about power requirements.

Posted by: Sunspot Mar 17 2006, 07:08 PM

Was Spirit supposed to drive today?

http://qt.exploratorium.edu/mars/spirit/forward_hazcam/2006-03-17/2F195787603EFFAQ67P1211R0M1.JPG

No movement.

Posted by: helvick Mar 17 2006, 07:21 PM

QUOTE (mars_armer @ Mar 17 2006, 06:37 PM) *
How sure are we of the 280 Whr "death" number? It's hard to believe that Spirit couldn't hunker down with overnight deep sleeps and infrequent comm passes and at least survive with much less than that. Could it be that SS was really talking about a minimum power level for usability, rather than a survival limit?

Well you can read how SS phrased it in http://athena1.cornell.edu/news/mubss/archive/2005_04.html on his blog. He isn't particularly explicit about what happens below that level just that "We think that the rovers can't survive at power levels much lower than 280 watt-hours". There have been other comments from the team to the rovers dying when power drops below 300whr but I can't find them at the moment.

There has already been some discussion on this in the http://www.unmannedspaceflight.com/index.php?showtopic=1718&st=15# thread. Any additional insight would be welcome.

Posted by: djellison Mar 17 2006, 08:29 PM

QUOTE (Sunspot @ Mar 17 2006, 07:08 PM) *
Was Spirit supposed to drive today?


Nope. Charging day

Doug

Posted by: akuo Mar 17 2006, 08:40 PM

QUOTE (Sunspot @ Mar 17 2006, 07:08 PM) *
Was Spirit supposed to drive today?
http://qt.exploratorium.edu/mars/spirit/forward_hazcam/2006-03-17/2F195787603EFFAQ67P1211R0M1.JPG
No movement.


That image is from yestersol, but there shouldn't be movement tosol anyway. http://marsrovers.jpl.nasa.gov/mission/status.html says that tosol (783) is a battery recharging sol.

BTW, I like how they have started to add the plans for the next few sols in the rover updates.

Posted by: Bob Shaw Mar 17 2006, 11:44 PM

QUOTE (mars_armer @ Mar 17 2006, 06:37 PM) *
How sure are we of the 280 Whr "death" number? It's hard to believe that Spirit couldn't hunker down with overnight deep sleeps and infrequent comm passes and at least survive with much less than that. Could it be that SS was really talking about a minimum power level for usability, rather than a survival limit?

Edit: Plenty of discussion on this subject in http://www.unmannedspaceflight.com/index.php?s=&showtopic=1718. My impression is that we know a lot more about power availability than about power requirements.


I think there *are* certain genuine limits, such as with regard to the batteries and the way they get charged/discharged. Certainly, if they get frozen then they'll be damaged, and may take no more charge. That might leave us with a MER which the DSN can ping, but does little else, ie EOM.

Bob Shaw

Posted by: Oersted Mar 18 2006, 12:00 AM

I think we're all happy that the team was pretty conservative in their time estimates to reach a good slope on the hill. It is exactly that kind of planning that will make this situation most probably survivable. - Apart from that, this is reminding me more and more of Apollo 13's homecoming, when they were also scrounging for every little amp they could find anywhere, to power up the command module with the minimum power...

Posted by: nprev Mar 18 2006, 12:28 AM

On the weakly positive side, I hope that the wheel motor circuit is dead open (if it has to be open at all, I mean...rats! sad.gif ) This will at least remove a little bit of load from Spirit's energy budget, though I know that the other wheels will more than overwhelm this due to extra torque requirements. A short to any part of the vehicle chassis from a hanging wire or a blown winding could prove fatal at this point... ohmy.gif

Posted by: marsman Mar 18 2006, 01:39 AM

In today's press release below, there are a few additional tidbits of information about SPIRIT's wheel problem and current driving expectations.


Guy Webster (818) 354-6278
Jet Propulsion Laboratory, Pasadena, Calif.

Dwayne Brown/Erica Hupp (202) 358-1726/1237

NASA Headquarters, Washington


News Release: 2006-039 March 17, 2006

Mars Rovers Get New Manager During Challenging Period

NASA's long-lived Mars rovers demand lots of care as they age and the Martian winter approaches.

Dr. John Callas, newly named project manager for NASA's Mars Exploration Rover mission, is coordinating the work to meet these challenges. He is a scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. He was named project manager after earlier roles as science manager and deputy project manager for the Spirit and Opportunity rovers.

"It continues to be an exciting adventure with each day like a whole new mission," Callas said. "Even though the rovers are well past their original design life, they still have plenty of capability to conduct outstanding science on Mars. The JPL operations team and the remote science team working on the project are the best in the solar system at what they do. It is a pleasure and a privilege to lead such an outstanding team and great mission."

One of Spirit's six wheels has stopped working. Dragging that wheel, the solar-powered rover must reach a slope where it can catch enough sunshine to continue operating during the Martian winter. The period of minimum sunshine is more than 100 days away, but Spirit gets only enough power for about one hour per day of driving on flat ground. And the supply is dropping fast.

Spirit's right-front wheel became a concern once before, when it began drawing unusually high current five months after the January 2004 landing on Mars. Driving Spirit backwards redistributed lubricant and returned the wheel to normal operation. This week, during the 779th Martian day of what was originally planned as a 90-Martian-day mission, the motor that rotates that wheel stopped working.

"It is not drawing any current at all," said JPL's Jacob Matijevic, rover engineering team chief. One possibility engineers are considering is that the motor's brushes, contacts that deliver power to the rotating part of the motor, have lost contact. The motors that rotate Spirit's wheels have revolved more than 13 million times, far more than called for in the rovers’ design.

Spirit's solar panels have been generating about 350 watt-hours of electricity daily for the past week. That is down about 15 percent since February and less than one-half of their output during the Martian summer.

The best spot for Spirit is the north-facing side of "McCool Hill," where it could spend the southern-hemisphere winter tilted toward the sun. Spirit finished studying a bright feature called "Home Plate" last week and is driving from there toward the hill. It has approximately 120 meters (about 390 feet) to go. Driving backwards with the right-front wheel dragging, the rover needs to stop and check frequently that the problem wheel has not snagged on anything and caused other wheels to slip excessively. Expected progress is around 12 meters (40 feet) per day under current conditions.

Opportunity is closer to the equator, so does not need to winter on a slope like Spirit. Opportunity spent most of the past four months at "Erebus Crater." It examined layered outcrops, while the rover team determined and tested a strategy for dealing with degraded performance by a motor in the shoulder of its robotic arm. Opportunity left Erebus this week and is on a 2 kilometer (1.2 mile) journey to a giant crater called "Victoria."

Callas has worked on the Mars rovers' mission since 2000 and five other Mars missions since joining JPL in 1987. He succeeds Jim Erickson, who switched to a leadership role with NASA's Mars Reconnaissance Orbiter. Callas grew up near Boston and graduated from Tufts University, Medford, Mass. He earned his doctorate in physics from Brown University, Providence, R.I.

JPL, a division of the California Institute of Technology, Pasadena, manages the Mars Exploration Rover and Mars Reconnaissance Orbiter projects for NASA's Science Mission Directorate.

Posted by: odave Mar 18 2006, 02:42 AM

QUOTE (marsman @ Mar 17 2006, 08:39 PM) *
News Release: 2006-039
<snip>
The period of minimum sunshine is more than 100 days away
<snip>
It has approximately 120 meters (about 390 feet) to go. [...] Expected progress is around 12 meters (40 feet) per day under current conditions.


Those numbers make me feel better, though I know anything can happen at any time. I assume the 120 meter figure is to the nearest possible "good" slope. Here's hoping Spirit can make it to a windy spot too!

wheel.gif wheel.gif wheel.gif

Posted by: Steve Mar 18 2006, 02:59 AM

QUOTE (marsman @ Mar 17 2006, 08:39 PM) *
NASA's long-lived Mars rovers demand lots of care as they age and the Martian winter approaches.

Dr. John Callas, newly named project manager for NASA's Mars Exploration Rover mission, is coordinating the work to meet these challenges. He is a scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. He was named project manager after earlier roles as science manager and deputy project manager for the Spirit and Opportunity rovers.

Let me make a few off-topic comments.
This change must not have been unexpected. A biographical sketch of Callas appears in a recent report he co-authored: http://marstech.jpl.nasa.gov/tdaPublications/DistribOpsfortheMERMisswiththeSciActivityPlanner.pdf

QUOTE
Dr. John L. Callas received his Bachelor's degree in Engineering from Tufts University in 1981 and his Masters and Ph.D. in Physics from Brown University in 1983 and 1987, respectively. After completing his doctorate in elementary particle physics in 1987, he joined the Jet Propulsion Laboratory in Pasadena, California to work on advanced spacecraft propulsion, which included such futuristic concepts as electric, nuclear and antimatter propulsion. In 1989 he began work supporting the exploration of Mars with the Mars Observer mission and has since worked on seven Mars missions. In 2000, Dr. Callas was asked to join the Mars Exploration Rover (MER) Project as the Science Manager. Dr. Callas continues as the Science Manager for the highly successful Spirit and Opportunity rovers. Recently, Dr. Callas has begun serving as a Mission Manager on MER, as an additional duty, as the rovers continue their great success on the surface of Mars. In addition to his Mars work, Dr. Callas is involved in the development of instrumentation for astrophysics and planetary science, and teaches mathematics at Pasadena City College as an adjunct faculty member. In his spare time, he mentors students interested in science and works with schools classrooms on science projects.

His 11 publications listed in the Astrophysical Data System (1983-2006) focus on remote sensing involving spacecraft using the radio and gamma regions of the spectrum.

Posted by: Jeff7 Mar 18 2006, 03:48 AM

Wow, looking at today's hazcam footage http://qt.exploratorium.edu/mars/spirit/forward_hazcam/2006-03-17/. (I might be a bit behind on this though, so forgive me if this is old news.)
Looks like it's doing pretty well, considering a totally frozen wheel.
It also looks like there might be more salt deposits there by the wheel.

Posted by: Sunspot Mar 18 2006, 08:41 PM

http://qt.exploratorium.edu/mars/spirit/rear_hazcam/2006-03-18/2R195964770EFFAQ75P1311R0M1.JPG

Sort of moved... I wonder what they were trying to do.

Posted by: mars_armer Mar 18 2006, 09:10 PM

Looks like too much slip (yawing to the left).

RF wheel, from http://qt.exploratorium.edu/mars/spirit/forward_hazcam/2006-03-18/2F195964705EFFAQ75P1213R0M1.JPG:



LF wheel, from http://qt.exploratorium.edu/mars/spirit/rear_hazcam/2006-03-18/2R195964770EFFAQ75P1311R0M1.JPG:

Posted by: mars_armer Mar 18 2006, 09:25 PM

Left rear wheel:



Left front wheel:



Looks like a good thing that it stopped. This is a dicey situation given the RF wheel problem.

I wonder if there's any advantage to be gained by steering the RF?

Posted by: Shaka Mar 18 2006, 10:20 PM

QUOTE (mars_armer @ Mar 18 2006, 11:25 AM) *
Left rear wheel:



Left front wheel:



Looks like a good thing that it stopped. This is a dicey situation given the RF wheel problem.

I wonder if there's any advantage to be gained by steering the RF?

I guess I'm not as adept at understanding the 'language' of the wheels as you are. Can you explain how to interpret the haz photos? I would say that the left-rear wheel (facing front) has run into the 'popcorn mesa' and been unable to climb it (or else we just stopped at this point by programming). As a result the other wheels churned a bit and the forward wheels (facing aft) slid a little to the left before we stopped. Can we carry on and run over the popcorn, or do we need to skirt it to the left? Or is that what we are about to find out? unsure.gif

Posted by: mars_armer Mar 18 2006, 10:29 PM

Sorry for the flood of pictures, but here's one more corrected view that makes it easy to see how much they pivoted around the RF wheel:



About 45 degree yaw. I take back what I said... the situation doesn't seem too bad; they can probably just back straight up with no problem.

QUOTE (Shaka @ Mar 18 2006, 02:20 PM) *
I guess I'm not as adept at understanding the 'language' of the wheels as you are. Can you explain how to interpret the haz photos? I would say that the left-rear wheel (facing front) has run into the 'popcorn mesa' and been unable to climb it (or else we just stopped at this point by programming). As a result the other wheels churned a bit and the forward wheels (facing aft) slid a little to the left before we stopped. Can we carry on and run over the popcorn, or do we need to skirt it to the left? Or is that what we are about to find out? unsure.gif

I'm just guessing like everyone else. Looks to me like one of two things happened. Either they lost traction on the right middle/rear wheels (the ones leading the stuck wheel as they drive backwards), and the other 3 wheels pivoted them around the dragging wheel. Or the stuck wheel snagged a stubborn subsurface rock. Either way, you need to back up, change direction a bit, and move along.

Presumably this kind of occurrence will be common from now on. I would think JPL is working on algorithm enhancements to prevent and/or automatically recover from situations like this so they don't lose driving opportunities.

Posted by: mhoward Mar 19 2006, 12:20 AM

Navcam mosaic from from Sol 781, showing where we started dragging:

http://www.flickr.com/photo_zoom.gne?id=114364644&size=o

Posted by: Jeff7 Mar 19 2006, 07:12 AM

QUOTE (mars_armer @ Mar 18 2006, 05:29 PM) *
Sorry for the flood of pictures, but here's one more corrected view that makes it easy to see how much they pivoted around the RF wheel:



About 45 degree yaw. I take back what I said... the situation doesn't seem too bad; they can probably just back straight up with no problem.
I'm just guessing like everyone else. Looks to me like one of two things happened. Either they lost traction on the right middle/rear wheels (the ones leading the stuck wheel as they drive backwards), and the other 3 wheels pivoted them around the dragging wheel. Or the stuck wheel snagged a stubborn subsurface rock. Either way, you need to back up, change direction a bit, and move along.

Presumably this kind of occurrence will be common from now on. I would think JPL is working on algorithm enhancements to prevent and/or automatically recover from situations like this so they don't lose driving opportunities.


I don't know - look at the hazcam pics in the drive direction. It looks like they might have made an intentional end-of-drive turn.
And look at the tracks - they are fairly straight despite the draggin wheel. It seems like they're compensating reasonably well, possibly with a modification of the previous 5-wheel mode.

Posted by: Bobby Mar 19 2006, 08:54 AM

With the wheel now turned completely sideways. How much stress can the wheel take? Is there a chance that driving with the wheel turned sideways like this rip the wheel off?

http://qt.exploratorium.edu/mars/spirit/forward_hazcam/2006-03-18/2F195964602EFFAQ74P1209R0M1.JPG

And if Spirit did lose the wheel. Can it drive ok with 5 wheels??? unsure.gif

Hope for a Dust Devil soon also dd.gif

Posted by: djellison Mar 19 2006, 09:10 AM

I can't believe I'm saying this again....there is no evidence that a dust devil ever cleaned Spirit. Some of the cleaning events happened overnight. You don't get DD's at night. Further more - the fact that there was a clear lack of cleaning 'downwind' from the HGA shows that it wasnt a spiralling whirlwind, but simply strong local winds in a constant direction that cleaned Spirit.

What we need is a big hill - the sort of place that has strong winds - not a DD - not to mention the fact that the DD season is long finished.

Doug

Posted by: pirex Mar 19 2006, 01:27 PM

QUOTE (djellison @ Mar 19 2006, 09:10 AM) *
I can't believe I'm saying this again....there is no evidence that a dust devil ever cleaned Spirit. Some of the cleaning events happened overnight. You don't get DD's at night. Further more - the fact that there was a clear lack of cleaning 'downwind' from the HGA shows that it wasnt a spiralling whirlwind, but simply strong local winds in a constant direction that cleaned Spirit.

What we need is a big hill - the sort of place that has strong winds - not a DD - not to mention the fact that the DD season is long finished.

Doug


Doug,

Your comments sound interesting. I have never heard about strong winds other than DDs? Do you have any info on this?

Posted by: djellison Mar 19 2006, 01:42 PM

Listen to or read the Steve Squyres Q'n'A I did .

http://www.unmannedspaceflight.com/index.php?showtopic=1683

Doug

Posted by: jaywee Mar 19 2006, 04:12 PM

QUOTE (mhoward @ Mar 19 2006, 01:20 AM) *
Navcam mosaic from from Sol 781, showing where we started dragging:

http://www.flickr.com/photo_zoom.gne?id=114364644&size=o

I wonder - doesn't the dragged track look a bit like the Magic Carpet?

Posted by: mhoward Mar 19 2006, 06:11 PM

QUOTE (jaywee @ Mar 19 2006, 04:12 PM) *
I wonder - doesn't the dragged track look a bit like the Magic Carpet?


I thought exactly the same thing.

Posted by: Stardust9906 Mar 19 2006, 10:58 PM

QUOTE (Bobby @ Mar 19 2006, 08:54 AM) *
With the wheel now turned completely sideways. How much stress can the wheel take? Is there a chance that driving with the wheel turned sideways like this rip the wheel off?


I don't think the wheel has turned sideways. What has happened is that the Rover has slewed around so that it is sideways on.

Posted by: pirex Mar 19 2006, 11:15 PM

delete

Posted by: AndyG Mar 20 2006, 10:16 AM

QUOTE (mhoward @ Mar 19 2006, 06:11 PM) *
I thought exactly the same thing.

Is there a topographic/contour map for this area - the last I could find on the MER Mission site stops before Homeplate?

Andy

Posted by: RNeuhaus Mar 20 2006, 03:01 PM

I have a pair comments about Spirit's new situation.

First, I am thinking a possible better solution to minimize the dragging of the front right wheel is that the rover don't go straight in comparision to the troubled wheel but try to go in the same line as the troubled wheel. That is in order to minimize the width of friction. That is only a tought.

The other comment, the dragging wheel would provide a good chance to know better the different types of land: dark and light color which is the indication of the different degrees of sulfate process.

Meanwhile, I hope that at any moment the friction force will turn on again the troubled wheel during its struggling dragging.

Rodolfo

Posted by: djellison Mar 20 2006, 03:18 PM

QUOTE (RNeuhaus @ Mar 20 2006, 03:01 PM) *
First, I am thinking a possible better solution to minimize the dragging of the front right wheel is that the rover don't go straight in comparision to the troubled wheel but try to go in the same line as the troubled wheel. That is in order to minimize the width of friction. That is an only a tought.


I think you might be missing the problem. The problem is driving the wheel, not turning it. They can turn the wheel left and right, i.e. have it in the direction it would normally be for driving. What they can't do is DRIVE the wheel.

For comparison, Opportunity has a wheel that is steering-locked just off centre, but still driveable - and they're doing quite well with it.

Doug

Posted by: RNeuhaus Mar 20 2006, 03:29 PM

Good for the clarification. Thanks

Then why the wheel was not aligned to the direction. Let suppose that unaligned wheel was leading greater friction on the surface. From this view, I am re-thinking that the diagonal position (45 degree to the motion direction) is the best position that minimizes the friction because the wheel surface has small "carets"? that is perpendicular to the direction.

Rodolfo

Posted by: centsworth_II Mar 20 2006, 03:45 PM

QUOTE (RNeuhaus @ Mar 20 2006, 10:29 AM) *
Good for the clarification. Thanks

Then why the wheel was not aligned to the direction.

Rodolfo


I think they turned the wheel after stopping.

Posted by: Sunspot Mar 20 2006, 06:44 PM

According to the MER tracking pages imsages for sol 785 are down, but not on the exp' website, I thought there might be probalem with the site again, but images for Oppy are online... so maybe just a glitch on the Spirit side. Weird.

Posted by: Phil Stooke Mar 21 2006, 02:56 PM

This looks EXACTLY the same as Arad, Paso Robles and other less studied places where bright soil has been uncovered. It's salt-rich, not ice-rich.

Phil

Posted by: Sunspot Mar 21 2006, 08:05 PM

Interesting shots of the drag marks.......... still no driving though huh.gif

http://qt.exploratorium.edu/mars/spirit/pancam/2006-03-21/2P195962908EFFAQ67P2530L7M1.JPG

Posted by: slinted Mar 21 2006, 08:21 PM

Same as above, in false color
http://www.lyle.org/~markoff/processed/2P195962820EFFAQ67P2530L234567M1.JPG

Posted by: mhoward Mar 21 2006, 09:33 PM

QUOTE (slinted @ Mar 21 2006, 08:21 PM) *
Same as above, in false color
http://www.lyle.org/~markoff/processed/2P195962820EFFAQ67P2530L234567M1.JPG


Same as above, in context:

http://flickr.com/photo_zoom.gne?id=115977233&size=l

I like these three (very) false-color Pancam frames too. Different subject, though:

http://flickr.com/photo_zoom.gne?id=115977224&size=l

Posted by: Tesheiner Mar 21 2006, 10:01 PM

QUOTE (Sunspot @ Mar 21 2006, 09:05 PM) *
Interesting shots of the drag marks.......... still no driving though huh.gif

http://qt.exploratorium.edu/mars/spirit/pancam/2006-03-21/2P195962908EFFAQ67P2530L7M1.JPG


Well, some movement took place; at least looking to the "site/drive" id. which has changed from AQ75 (on sol 784) to the current id. AQ81. But I can't find any "post-drive" navcam mosaic to make a driving distance estimation.

Posted by: mhoward Mar 21 2006, 10:51 PM

QUOTE (Tesheiner @ Mar 21 2006, 10:01 PM) *
Well, some movement took place; at least looking to the "site/drive" id. which has changed from AQ75 (on sol 784) to the current id. AQ81. But I can't find any "post-drive" navcam mosaic to make a driving distance estimation.


The move to AQ81 was basically nothing. But wait! Now we're up to AQAE:

http://nasa.exploratorium.edu/mars/spirit/forward_hazcam/2006-03-21/2F196230651EFFAQAEP1213R0M1.JPG

Here's the view directly South on Sol 787, angled down 35 degrees to catch the dramatic wheel tracks:

http://www.flickr.com/photo_zoom.gne?id=116046426&size=l

Posted by: Shaka Mar 21 2006, 10:59 PM

QUOTE (mhoward @ Mar 21 2006, 12:51 PM) *
The move to AQ81 was basically nothing. But wait! Now we're up to AQAE:

Here's the view directly South on Sol 787, angled down 35 degrees to catch the dramatic wheel tracks:

Dramatic is right! Is it a fair conclusion that the 'popcorn' is actually granules of iron sulfate salts? This looks like a really major bed of the stuff.

Posted by: dilo Mar 21 2006, 11:02 PM

Very impressive turn, how did displaced so much white powder?!

 

Posted by: Ames Mar 21 2006, 11:15 PM

QUOTE (mhoward @ Mar 21 2006, 10:51 PM) *
The move to AQ81 was basically nothing. But wait! Now we're up to AQAE:

http://nasa.exploratorium.edu/mars/spirit/forward_hazcam/2006-03-21/2F196230651EFFAQAEP1213R0M1.JPG

Here's the view directly South on Sol 787, angled down 35 degrees to catch the dramatic wheel tracks:

http://www.flickr.com/photo_zoom.gne?id=116046426&size=l


Looks like the impediment of dragging the stuck wheel is actually bearing scientific fruit.

We are trenching wherever we go and serendipitously stumbling upon interesting soils.

Didn't someone say they wished the Mers had ploughs - now one of them does!

Nick

Posted by: Shaka Mar 21 2006, 11:29 PM

QUOTE (Ames @ Mar 21 2006, 01:15 PM) *
Looks like the bad news of dragging a wheel is bearing benifits.

We are trenching wherever we go and serendipitously stumbling upon interesting soils.

Didn't someone say they wished the Mers had ploughs - now one of them does!

Nick

Yeah, I wish it were retractable though. It's great fun in the sand, but I'm getting worried about when we get into the rocks. A worst-case scenario might be: two steps forward - one step back - turn - two steps forward - one step back - turn.... sad.gif
wheel.gif Hustle, guys! We have got to get to the Safe Zone! Stick to the sand until we get there. wheel.gif

Posted by: nprev Mar 22 2006, 12:07 AM

QUOTE (dilo @ Mar 21 2006, 03:02 PM) *
Very impressive turn, how did displaced so much white powder?!


That's really remarkable (again!)...still amazes me that this stuff exists in such discrete deposits so near the surface.

Just out of curiosity, does anyone know if potassium, sulphur, etc. salts decompose when exposed to typical Martian UV levels? Be interesting to know if this might be one big reason we don't see direct surface deposits.

Posted by: RNeuhaus Mar 22 2006, 03:00 AM

Due to the Spirit dragging surface, I hope to find some very interesting news soon from the wheel dragging mark. I won't be hoping to see any plant ancient roots but something novel thing hidden by the dust deposition. smile.gif So, come any birds to catch any alive worms! biggrin.gif

Rodolfo

Posted by: sranderson Mar 22 2006, 05:10 AM

QUOTE (Shaka @ Mar 21 2006, 03:59 PM) *
Dramatic is right! Is it a fair conclusion that the 'popcorn' is actually granules of iron sulfate salts? This looks like a really major bed of the stuff.


This could be percolation of salt-heavy groundwater, with evaporation at the surface leaving the salts, and then overcover of dust/sand.

Does anyone really understand the effects of evaporation through soils (from deep within the soil) in a low-pressure environment over millions of years? I wonder if the white salt beds and the odd formations (popcorn, like cave-popcorn, and blueberries, etc.) could be explained simply due to slow molecular water movement from within the the regolith and rock out to the atmosphere. The presence of underground water, even when frozen, with a thin atmosphere on the outside, sets up a strong molecule-by-molecule pumping gradient. It could fizz out into all kinds of formations similar to what are found in caves on earth.

Scott

Posted by: CosmicRocker Mar 22 2006, 06:13 AM

There you go, folks. Good work, let's take this lemon of a wheel and make lemonade of it. biggrin.gif It's going to be a pain to drag it along, but as several have noted, it will be an interesting running experiment, and as Rodolfo points out, the birds often follow our harvesting machines and earth-movers. We really don't seem to have much of a choice at this point, so let's make the most of it.

It looks as if it will be pretty useful for digging up the buried salt deposits. At first I was thinking the recent white patches were just places where Spirit scraped the soil away from the light-colored rock we have been driving over for several sols, but this turn really looks like the previous occurances of the fluffy sulfates.

Posted by: Marz Mar 22 2006, 05:43 PM

QUOTE (CosmicRocker @ Mar 22 2006, 12:13 AM) *
There you go, folks. Good work, let's take this lemon of a wheel and make lemonade of it. biggrin.gif It's going to be a pain to drag it along, but as several have noted, it will be an interesting running experiment, and as Rodolfo points out, the birds often follow our harvesting machines and earth-movers. We really don't seem to have much of a choice at this point, so let's make the most of it.


Cosmic Rocker must be in software design: A stuck wheel is a "feature", no extra charge. So what is the name for this useful tool? The Trenchifacator? The Aeolian Deposit Destratifier? tongue.gif

I wonder if we may also get luck in turning over many more pebbles and rocks to maybe see less weathered surfaces?

Another benefit will be the tracks will be much easier viewed from orbit: so over the years as they fade might give some useful clues to dust-movement rates across mars?

Posted by: Bubbinski Mar 22 2006, 07:12 PM

The "Trenchifacator"...I like that. The rovers' tracks and trenches have to be great for Mars soil science. I'd like to see a route map to where Spirit needs to go to stay safe and have a daily progress chart.

I'm not nearly skilled or knowledgeable enough to put together the route maps that other posters have put up (I'm just a very interested layman who wanted to get into space science past college but couldn't hack calculus). But I could try....I have MMB and Paint Shop Pro and some basic knowledge.

Edit: D'OH! I missed the pinned Spirit route map. I'm checking it out now.

Posted by: djellison Mar 22 2006, 07:32 PM

THE TRENCHINATOR - look for the new Q'n'A ( that's a full half hour long ) - we talk about trenchinating smile.gif

Posted by: Reckless Mar 22 2006, 10:42 PM

Faulty wheel? it's a pre-breaking devise for safety. Eat your heart out Volvo.
Roy F

Posted by: Sunspot Mar 23 2006, 12:00 AM

QUOTE (Reckless @ Mar 22 2006, 10:42 PM) *
Faulty wheel? it's a pre-breaking devise for safety. Eat your heart out Volvo.
Roy F


Oh great..the exploratorium is dead again. blink.gif blink.gif

Posted by: djellison Mar 23 2006, 12:12 AM

No it's not - Odyssey safe moded yesterday - expect a few days of blackout. sad.gif

Can't complain, she's a damn good messenger - last blackout was back before purgatory ohmy.gif

Doug

Posted by: mhoward Mar 23 2006, 02:09 AM

QUOTE (djellison @ Mar 23 2006, 12:12 AM) *
No it's not - Odyssey safe moded yesterday - expect a few days of blackout. sad.gif

Can't complain, she's a damn good messenger - last blackout was back before purgatory ohmy.gif

Doug


I was wondering why things were so quiet all of sudden. Thanks for filling us in.

Posted by: Sunspot Mar 23 2006, 11:30 AM

Weren't they using Odyssey to uplink commands to Spirit because of a communicatinos conflict with MRO? How are they going to handle communicating sith Spirit whle Odyssey is in safe mode?

Posted by: djellison Mar 23 2006, 11:43 AM

The rovers will look after themselves for days on end - but I'm sure they'll be able to do some sort of uplink if needs be.

Doug

Posted by: Bill Harris Mar 23 2006, 11:52 AM

QUOTE (sranderson @ Mar 21 2006, 11:10 PM) *
This could be percolation of salt-heavy groundwater, with evaporation at the surface leaving the salts, and then overcover of dust/sand.

Does anyone really understand the effects of evaporation through soils (from deep within the soil) in a low-pressure environment over millions of years? I wonder if the white salt beds and the odd formations (popcorn, like cave-popcorn, and blueberries, etc.) could be explained simply due to slow molecular water movement from within the the regolith and rock out to the atmosphere. The presence of underground water, even when frozen, with a thin atmosphere on the outside, sets up a strong molecule-by-molecule pumping gradient. It could fizz out into all kinds of formations similar to what are found in caves on earth.

Scott


There are a lot of things we don't/can't understand because of the time frames and environments involved.

Two years ago I started an oddball experiment creating my own Burns Formation. I got sandstone with the nastiest framboidal pyrite and let it oxidize to make a quantity of iron-plus_other_metals sulfates. Added this brew to a saturated solution of magnesium sulfate. Let it evaporate to dryness and continue to "dehydrate" over time. The slow "dehydration" from the "hydrated" mass of salt crystals has been interesting watching the 'fairy castle' structures grow. Looks rather like the "popcorn" masses we've seen lately.

Image attached.

I may redissolve the whole mass/mess and add a quantity of fine silica sand (as a matrix), no clays allowed.

--Bill

Posted by: AndyG Mar 23 2006, 02:26 PM

QUOTE (Bill Harris @ Mar 23 2006, 11:52 AM) *
Two years ago I started an oddball experiment creating my own Burns Formation. I got sandstone with the nastiest framboidal pyrite and let it oxidize to make a quantity of iron-plus_other_metals sulfates. Added this brew to a saturated solution of magnesium sulfate. Let it evaporate to dryness and continue to "dehydrate" over time. The slow "dehydration" from the "hydrated" mass of salt crystals has been interesting watching the 'fairy castle' structures grow. Looks rather like the "popcorn" masses we've seen lately.

Image attached.

Clearly biogenic. Oh, sorry - wrong Martian blog. wink.gif

Andy

Posted by: aldo12xu Mar 23 2006, 05:07 PM

Wow, Bill, that's really cool. Yes, it definitely looks like the strawberry textured nodules. Please keep the experiment going. I wonder what would take to get actual concretions to form?




Posted by: Bill Harris Mar 23 2006, 07:12 PM

After the water evaporated from the brew and it became a block of sulfate crystals, I left it for several months in a sunny window sill with a loose-fitting cover to keep dust and other "aeolian" deposition out. The textured features seen here are light, fluffy microcrystalline structures thaty have grown from the saturated sulfate salt mass. The thickness is between 5 and 35mm. I really should have been photographing their development all along, they were a suprise to me. I have noted that these sulfate salts have been pulling moisture from the air for their reaction. I expected this-- the pyritic sandstones react in containers in my lab/office using only humidity from the air. This may be an odd element of the Martian hydrologic cycle (as noted in the current Geology, and as noted here).

Instead of redissolving this mass and starting over I'll let it continue and do another vat with fresh sulfates and fine silica sand. I have lots of framboidal pyrite wanting to react to make the iron sulfate brew. I may try "seeding" the saturated sand mass with hematite, pyrite, etc.

--Bill

Posted by: Gray Mar 23 2006, 07:19 PM

QUOTE (Bill Harris @ Mar 23 2006, 07:12 PM) *
.... I'll let it continue and do another vat with fresh sulfates and fine silica sand. I have lots of framboidal pyrite wanting to react to make the iron sulfate brew.

--Bill




Bill,
Perhaps you could grind up some basalt and use it instead of a silica (quartz?) sand. Or would that be adding too much iron to the mixture?

Posted by: Bill Harris Mar 23 2006, 09:52 PM

I don't have a ball-mill handy and I'm not sure what variables the weathering of the pyroxene and feldspar would introduce into the equation (although this mix ought to be more real-life). I'm looking for a neutral matrix and can sieve commercial sand through 50 to 100 screen.

--Bill

Posted by: sranderson Mar 24 2006, 02:35 AM

QUOTE (Bill Harris @ Mar 23 2006, 04:52 AM) *
There are a lot of things we don't/can't understand because of the time frames and environments involved.

Two years ago I started an oddball experiment creating my own Burns Formation. [snip]

--Bill


This is great stuff Bill. Such structures seem to require water evaporation, and are modified by water in the air. Ummm.. Too bad you can't reduce the pressure some.

Scott

Posted by: RGClark Mar 24 2006, 03:07 AM

QUOTE (slinted @ Mar 21 2006, 08:21 PM) *
Same as above, in false color
http://www.lyle.org/~markoff/processed/2P195962820EFFAQ67P2530L234567M1.JPG



Thanks for the image slinted. This really brings out the similarity to the "Magic Carpet" feature that jaywee and mhoward mentioned.
Like the "Magic Carpet" seen when the air bags were retracted, this arose from material been pressed down and dragged away.
On the MarkCarey.com/mars forum there is discussion that this material may be or may have been moist:

Dark subsurface, blue ripples, red sand....
http://www.markcarey.com/mars/discuss-33889-dark-subsurface-blue-ripples-red-sand.html

If there were thin interstitial ice from atmospheric deposition this ice may have been melted by the squeezing and dragging of the wheel.

cf.

From: Robert Clark - view profile
Date: Wed, Jan 4 2006 1:02 pm
Email: "Robert Clark" <rgregorycl...@yahoo.com>
Groups: sci.astro, alt.sci.planetary, sci.physics
Subject: Could We Make A "Solar Still" On Mars?
http://groups.google.com/group/sci.astro/msg/f76e921c4b865f2e



Bob Clark

Posted by: silylene Mar 24 2006, 02:19 PM

QUOTE (RGClark @ Mar 24 2006, 03:07 AM) *
If there were thin interstitial ice from atmospheric deposition this ice may have been melted by the squeezing and dragging of the wheel.


That is highly unlikely, at least with pure ice. Ice is capable of compression melting only over a very small temperature range at reasonable pressures (e.g. down to about -10C for an ice skate), and even this requires significantly higher pressure than the wheel could exert (* caveat: pure ice, that is). See, for example "Why Ice is Slippery" by Rosenberg, Dec 2005, Physics Today pp 50-55.

I am unaware of any data measuring the phase diagram of highly concentrated sulfate/sulfurous brine. I think it is likely that Martian ices, if they are present, would be sulfate/sulfurous brines. I think it is likely that the water/ice phase transitions of such a brine could occur at lower temperatures than pure ice, perhaps -40C; but I don't know if said frozen brines could be compressed to form a liquid at reasonable temperatures.

Posted by: Decepticon Mar 24 2006, 02:38 PM

It's amazing how a malfunction has also caused a neat discovery.

Posted by: djellison Mar 24 2006, 02:49 PM

Don't forget that the pressure is approx 1.5% that of earth's pressure. It is exceptionally unlikely that liquid water, even one highly rich in dissolved minerals, cound exist at that surface temperature and pressure. Ice, if present, would most probabyl sublime to the gas phase.

Nick Hoffman explained it best over at THZ when replying to Robet.

Subject: No


smile.gif

Doug

Posted by: RGClark Mar 25 2006, 12:21 AM

QUOTE (silylene @ Mar 24 2006, 02:19 PM) *
That is highly unlikely, at least with pure ice. Ice is capable of compression melting only over a very small temperature range at reasonable pressures (e.g. down to about -10C for an ice skate), and even this requires significantly higher pressure than the wheel could exert (* caveat: pure ice, that is). See, for example "Why Ice is Slippery" by Rosenberg, Dec 2005, Physics Today pp 50-55.

I am unaware of any data measuring the phase diagram of highly concentrated sulfate/sulfurous brine. I think it is likely that Martian ices, if they are present, would be sulfate/sulfurous brines. I think it is likely that the water/ice phase transitions of such a brine could occur at lower temperatures than pure ice, perhaps -40C; but I don't know if said frozen brines could be compressed to form a liquid at reasonable temperatures.


That's a fair point. But the dragging also would have provided frictional heat.


Bob Clark

Posted by: RGClark Mar 25 2006, 12:47 AM

QUOTE (djellison @ Mar 24 2006, 02:49 PM) *
Don't forget that the pressure is approx 1.5% that of earth's pressure. It is exceptionally unlikely that liquid water, even one highly rich in dissolved minerals, cound exist at that surface temperature and pressure. Ice, if present, would most probabyl sublime to the gas phase.

Nick Hoffman explained it best over at THZ when replying to Robert.

Subject: No
smile.gif

Doug


It is now well known that salts can lower the freezing point of water. It's not as well known but also key that they can also lower the required pressure for liquid water. This is discussed here:

On the possibility of liquid water on present-day Mars.
Haberle, Mckay, Schaeffer, Cabrol, Grin, Zent, and Quinn.
Journal of Geophysical Research, no. E10, p. 23,317-23,326, Oct. 25, 2001
http://www.agu.org/pubs/crossref/2001/2000JE001360.shtml

"We now examine the effect of dissolved salts on the potential for melting. Pure water is unlikely on Mars since salts are believed to be a significant component of the Martian soil [Clark and Van Hart, 1981]. The presence of salts will lower the melting point and reduce the equilibrium vapor pressure of the solution. An example of the effect of a NaCl brine on the potential for melting is shown in Figure 7. In this example, the eutectic point is 251 K and the equilibrium vapor pressure of the solution at that temperature is 1.23 mbar. Clearly, the presence of salts greatly expands the regions where melting could occur and increases the total time such conditions might exist. In this particular example, virtually the entire planet (except the polar regions) experiences conditions favorable for melting at some point during the year, including the Tharsis plateau.
...
"For the NaCl brine mentioned above, boiling would not occur at its eutectic anywhere on Mars since the surface pressure never falls below 2.60 mbar anywhere on the planet during the year."
On the possibility of liquid water on present-day Mars, p. 23,321-23,322


There is also this:

37th DPS Meeting, 4-9 September 2005
Session 24 Mars III
Oral, Tuesday, September 6, 2005, 2:00-3:50pm, Music Concert Hall
--------------------------------------------------------------------------------
[24.09] New evidence for recent climate control as the source of the equatorial water equivalent hydrogen regions on Mars.
S.M. Nelli, J.R. Murphy (NMSU), W.C. Feldman (LANL)

The origin of the longitudinally confined equatorial water equivalent hydrogen (WEH) regions on Mars is disputed. Current arguments for their existence are: 1) recent ice age, 2) near-surface water table, 3) recent sublimation of the CO2 veneer of the south residual polar cap, and 4) in equilibrium with the current atmospheric conditions on Mars. The NASA Ames GCM is used to explore current Martian climate conditions as the source for the equatorial WEH-rich regions on Mars. There is a correlation between the simulated total annual deposition (but not accumulated) pattern of water ice and the equatorial WEH-rich regions on Mars. Model results indicate that local nighttime thermodynamics and thermal inertia/topography create bulk water ice precipitation regions over Arabia and Tharsis. Nighttime air in contact with the ground cools via radiation and conduction, precipitating water ice at locations where the local near-surface atmospheric temperature falls below the dew point. The highest topographic longitudes, coincident with the lowest surface thermal inertias, beget the lowest temperatures, resulting in a longitudinal wave two pattern of water ice deposition upon Arabia and Tharsis. These current longitudinally confined "wet" conditions provide water vapor that is readily available for adsorption by hydratable minerals during the night.

Support for this project comes from NASA Planetary Atmospheres Programs (NAG5-12123) and by the DOE through Laboratory Directed Research and Development funds.
--------------------------------------------------------------------------------
http://www.aas.org/publications/baas/v37n3/dps2005/766.htm


Bob Clark

Posted by: silylene Mar 25 2006, 01:09 AM

QUOTE (RGClark @ Mar 25 2006, 12:21 AM) *
That's a fair point. But the dragging also would have provided frictional heat.


Bob Clark


I think the frictional heat is minimal, and not enough to melt briney ice. Drag a wheel across your hand, the warming is at most a few degrees.

Posted by: CosmicRocker Mar 25 2006, 06:54 AM

Yeah. The frictional heat seems as if it would be hardly be worth mentioning. If there were significant water molecules this close to the surface and this close to the equator, they would have been detected by the orbiters, wouldn't they have?

Isn't this just really fine stuff agglomerating with the help of electrostatic forces, or other weak forces?

Posted by: djellison Mar 25 2006, 09:10 AM

QUOTE (CosmicRocker @ Mar 25 2006, 06:54 AM) *
If there were significant water molecules this close to the surface and this close to the equator, they would have been detected by the orbiters, wouldn't they have?


EXACTLY - and Odyssey hasn't done that.

Nick has it right.
[/color]
QUOTE
[color="black"]If more or less any random bit of Mars had saturated brines a few cm below the surface then there would be wetter areas with standing brine pools - lakes, streams, swamps and the like. The atmosphere of Mars is WAY too dry for that scenario - just the shallow brine would totally saturate the atmosphere through diffusion. Then you have to look at how the brine would be restored?

It may "look" like mud, but there's no way it can actually *be* mud. Focussing on your desires and hopes rather than scientific reality may be warm and cosy but it's totally incorrect and will lead you up a long and painful blind alley.

Mars is a very difficult planet to comprehend because [bold]it is not Earth-like[/bold]. All our human instincts and ideas are irrevocably shaped by our birth, education, and multi-million year Mammalian evolution on Earth. It is a hard buit profitable exercise to think yourself outside of that box. If you persist in believing only your eyes and your instincts, you will never understand Mars.


http://www.habitablezone.com/nexus/index.asp?svcpt=space

Personally - I see no evidence other that 'it looks a bit like mud' - and good scientific reasoning that it can't be. It's a no brainer.If it WERE such a material - where's the cohesion to the wheels?



Doug

Posted by: Sunspot Mar 25 2006, 10:23 AM

Does Spirit not have enough energy for any direct to Earth communication sessions (sending images like Opportunity)? This Odyssey blackout couldn't have come at a worse time for Spirirt. ohmy.gif

Posted by: Tesheiner Mar 25 2006, 11:49 AM

That's Murphy's Law. sad.gif

Posted by: nprev Mar 25 2006, 11:54 AM

I mentioned this before (probably on another thread), but back in my junior-high days for a science fair I built a Mars Jar (post-Viking) & mixed the soil in accordance with VL1 results. I assumed that the potassium and sulfur were oxides, so I purchased the pure stuff accordingly...and both of them were snow white.

To my horror at the time, the oxides refused to mix well with the red clays & iron oxide that constituted most of the soil; I ended up with distinct white layers in the final product (as viewed from the side of the transparent enclosure). Back then, I thought that this was my own sloppy procedure; after Spirit's repeated exposure of just such layers, I am beginning to believe that my model was pretty accurate after all! tongue.gif

Posted by: Bill Harris Mar 25 2006, 12:00 PM

This is a no-brainer: it ain't mud.

We have an exceedingly fine powder that compacts under pressure, just as we've seen at Oppy's Magic Carpet, many Mossbauer presses and countless wheel tracks.

It could be mud, though. There could also be lizard bones and @lien @rtifacts on the ground and windmills on the horizon, but that is less likely, too.

--Bill

Posted by: David Mar 25 2006, 01:33 PM

QUOTE
Mars is a very difficult planet to comprehend because it is not Earth-like. All our human instincts and ideas are irrevocably shaped by our birth, education, and multi-million year Mammalian evolution on Earth.


I'll buy the education, and maybe the birth, but the "multi-million year Mammalian evolution" is a bit much. Future humans raised on Mars will/would have just as "instinctual" a knowledge of how Martian surface materials behave as we Earthlings do about the way materials behave on Earth. It's just a matter of repeatedly observing conditions. I'm sure that some people who move from the tropics to a temperate zone are shocked to discover that water falls from the sky as frozen crystals at some times of the year, but they are not evolutionarily conditioned to be unable to learn how snow and ice behave. Human minds are very capable of adapting to circumstances.

Posted by: Cugel Mar 25 2006, 03:07 PM

QUOTE (David @ Mar 25 2006, 02:33 PM) *
I'll buy the education, and maybe the birth, but the "multi-million year Mammalian evolution" is a bit much. Future humans raised on Mars will/would have just as "instinctual" a knowledge of how Martian surface materials behave as we Earthlings do about the way materials behave on Earth. It's just a matter of repeatedly observing conditions. I'm sure that some people who move from the tropics to a temperate zone are shocked to discover that water falls from the sky as frozen crystals at some times of the year, but they are not evolutionarily conditioned to be unable to learn how snow and ice behave. Human minds are very capable of adapting to circumstances.


Adapting to the near vacuum of Mars would certainly take a few repeating observations!
rolleyes.gif

Posted by: RGClark Mar 25 2006, 03:17 PM

QUOTE (silylene @ Mar 25 2006, 01:09 AM) *
I think the frictional heat is minimal, and not enough to melt briney ice. Drag a wheel across your hand, the warming is at most a few degrees.

Drag a fifty pound wheel across your hand slowly, the heating can be more.
In any case assuming salts, daytime temperatures and pressures could already be within the range for liquid water.


Bob Clark

Posted by: RGClark Mar 25 2006, 03:52 PM

QUOTE (CosmicRocker @ Mar 25 2006, 06:54 AM) *
Yeah. The frictional heat seems as if it would be hardly be worth mentioning. If there were significant water molecules this close to the surface and this close to the equator, they would have been detected by the orbiters, wouldn't they have?

Isn't this just really fine stuff agglomerating with the help of electrostatic forces, or other weak forces?


In discussions on the internet one should always endeavor to maintain civility in your discussions.
But I have to say: they HAVE been detected from orbit.
In the thread to the sci.astro post I linked to above I discussed this further. To summarize, the Mars Odyssey GRS spectrometer team found seasonal variations in the amount of water close to the surface. They concluded this is due to ice or frost deposition including at near equatorial latitudes.
And both MGS and Mars Express found seasonal variations in the infrared spectral signature of water including at near equatorial latitudes. The MGS team concluded this is due to seasonal variations in the bound water content. I argue this overwhelming implies there are seasonal variations in the liquid water content at the surface to form the seasonal variations in these hydrated minerals.
The Mars Express team argued as did the Mars Odyssey GRS team that the seasonal variations are due to frost/ice deposition. But this deposition occurs even during the seasonal periods the daytime temperature would be within the range for liquid water.

I discuss this here:

From: Robert Clark
Date: Sat, Feb 11 2006 9:32 pm
Email: "Robert Clark" <rgregorycl...@yahoo.com>
Groups: sci.astro, alt.sci.planetary, sci.physics, sci.geo.mineralogy
Subject: Re: Could We Make A "Solar Still" On Mars?
http://groups.google.com/group/sci.astro/msg/95e5bae350f8c285

I must say I find this to be of bombshell importance. I'm quite surprised there was no discussion of this on the online discussions of the 2006 Lunar and Planetary Science Conference results.


Bob Clark

Posted by: djellison Mar 25 2006, 03:57 PM

Under 1/3rdG , we're talking less than 10kg per wheel, spread over something like 50-100 sqcm. Take a 10kg weight, drag it thru sand, very very slowly, and the net result is NOTHING. If there's any heating at all, I'd be astonished if it was more than a single degree. To suggest that the friction of wheel drag would cause heating to generate liquid state water is just silly. Consider the daily temperature swing, it's already 50 degrees+, and if you include the fact that we're approaching winter - then we'd have had much warmer temperature in the last 300 sols than anything the frankly laughable concept of wheel drag temperature increases.

If one or two degrees now can liberate liquid water onto the surface - then Gusev would have been a muddy bog for the past 300 sols.

You're just grabbing at straws.

Doug

Posted by: kungpostyle Mar 25 2006, 04:01 PM

QUOTE (RGClark @ Mar 25 2006, 10:17 AM) *
Drag a fifty pound wheel across your hand slowly, the heating can be more.
In any case assuming salts, daytime temperatures and pressures could already be within the range for liquid water.


Bob Clark



On Mars, given the reduced gravity, I believe there is far less than 50 pounds per square unit (use which ever you prefer) exerted on the surface. I Did the rough math once but don't have it handy.


In any case the surface of Mars is routinely heated above 32ºF by solar heating, I would assume this heat would easily transmit through the upper few inches of soil, and any water would volatilize.

I believe any water this close to the surface, as seen in data from orbiting spacecraft exists only hydrated minerals, that is to say water molecules bonded to and trapped in mineral structures.

I could be dead wrong on any or all of this, so take it for what is.

Posted by: alan Mar 25 2006, 04:10 PM

46 images down from spirit, I guess this means that Odyssey is back.

Posted by: djellison Mar 25 2006, 04:19 PM

QUOTE (alan @ Mar 25 2006, 04:10 PM) *
46 images down from spirit, I guess this means that Odyssey is back.


Or they just did a 4 hr DTE HGA pass and her battery's now flat smile.gif

The same site at which you can get UHF session data, also has uplink data for Odyssey. It's not up to date yet, but this is what was done last time Odyssey safed.

CODE
0796506249:0 2005-087T19:40:39 ci2997 d:/seq/crc_check_file_seq_pt1            RELATV CF6DDCD5
0796584494:1 2005-088T17:24:44 ci2998 d:/seq/crc_check_file_seq_pt2            RELATV CCA359FA
0797013133:8 2005-093T16:28:43 ci2262 d:/seq/safe_mode_daily_diagnostics       RELATV 47A47FFE
0797091539:9 2005-094T14:15:29 ci2262 d:/seq/safe_mode_daily_diagnostics       RELATV 47A47FFE
0797188568:1 2005-095T17:12:37 ci3007 d:/seq/rexmit_050405_upgo                RELATV 3C447CF7
0797189118:1 2005-095T17:21:47 ci2262 d:/seq/safe_mode_daily_diagnostics       RELATV 47A47FFE
0797197803:1 2005-095T19:46:32 ci2698 d:/seq/heap_reinit                       RELATV 53EA825F
0797203805:1 2005-095T21:26:34 ci3005 d:/seq/map_sm_recovery_upgo              RELATV 939F56E1
0797268565:2 2005-096T15:25:54 ci2951 d:/seq/map_sm_recovery_reinits           RELATV F115581C

Doug

Posted by: RGClark Mar 25 2006, 04:29 PM

QUOTE (djellison @ Mar 25 2006, 03:57 PM) *
Under 1/3rdG , we're talking less than 10kg per wheel, spread over something like 50-100 sqcm. Take a 10kg weight, drag it thru sand, very very slowly, and the net result is NOTHING. If there's any heating at all, I'd be astonished if it was more than a single degree. To suggest that the friction of wheel drag would cause heating to generate liquid state water is just silly. Consider the daily temperature swing, it's already 50 degrees+, and if you include the fact that we're approaching winter - then we'd have had much warmer temperature in the last 300 sols than anything the frankly laughable concept of wheel drag temperature increases.

If one or two degrees now can liberate liquid water onto the surface - then Gusev would have been a muddy bog for the past 300 sols.

You're just grabbing at straws.

Doug


Well I don't agree with you on the effect of this pressure and dragging. Keep in mind we're not talking about inch thick ice here. We considering interstitial ice layers that may be on the order of 10's to 100's of microns thick. This is on the range of the thickness of a snowflake.
Also remember the wheels are black so will absorb more heat. And the rims at least are metal which will also cause more heat to be absorbed. Now imagine these twenty pound wheels, warmer than surrounding temperatures, scraping across snowflakes on the ground.


Bob Clark

Posted by: RGClark Mar 25 2006, 04:41 PM

QUOTE (djellison @ Mar 25 2006, 04:19 PM) *
Or they just did a 4 hr DTE HGA pass and her battery's now flat smile.gif

The same site at which you can get UHF session data, also has uplink data for Odyssey. It's not up to date yet, but this is what was done last time Odyssey safed.

CODE
0796506249:0 2005-087T19:40:39 ci2997 d:/seq/crc_check_file_seq_pt1            RELATV CF6DDCD5
0796584494:1 2005-088T17:24:44 ci2998 d:/seq/crc_check_file_seq_pt2            RELATV CCA359FA
0797013133:8 2005-093T16:28:43 ci2262 d:/seq/safe_mode_daily_diagnostics       RELATV 47A47FFE
0797091539:9 2005-094T14:15:29 ci2262 d:/seq/safe_mode_daily_diagnostics       RELATV 47A47FFE
0797188568:1 2005-095T17:12:37 ci3007 d:/seq/rexmit_050405_upgo                RELATV 3C447CF7
0797189118:1 2005-095T17:21:47 ci2262 d:/seq/safe_mode_daily_diagnostics       RELATV 47A47FFE
0797197803:1 2005-095T19:46:32 ci2698 d:/seq/heap_reinit                       RELATV 53EA825F
0797203805:1 2005-095T21:26:34 ci3005 d:/seq/map_sm_recovery_upgo              RELATV 939F56E1
0797268565:2 2005-096T15:25:54 ci2951 d:/seq/map_sm_recovery_reinits           RELATV F115581C

Doug


I had suggested that one method to observe indications of moisture by the rovers would be to cover an area at night (to preserve deposited frost/ice) and uncover it in the morning:

From: Robert Clark
Date: Thurs, Jan 19 2006 12:15 pm
Email: "Robert Clark" <rgregorycl...@yahoo.com>
Groups: sci.astro, alt.sci.planetary, sci.physics
Subject: Re: Could We Make A "Solar Still" On Mars?
http://groups.google.com/group/sci.astro/msg/045193664ad43276

I was wondering if this is what happened with this material revealed in the trench dug by the stuck wheel.
Is there a way to check these data streams to see at what time the wheels were left in place and what time they were moved?




Bob Clark

Posted by: djellison Mar 25 2006, 05:20 PM

QUOTE (RGClark @ Mar 25 2006, 04:29 PM) *
Now imagine these twenty pound wheels, warmer than surrounding temperatures, scraping across snowflakes on the ground.
Bob Clark


Let's go totally and utterly nuts - let's say the temperature increase is as much as 5 degrees ( I doubt it would be 1/10th of that)

You're only raising things to a temperature they would have exceeded, regularly, for prolonged periods, all summer. If you're suggestion is that wheel friction is causing an increase in temperature of a few degrees, thus melting ice content of the soil, then that same ice would have been melted just by the warmer temperature of the summer, for hundreds of sols, across the whole planets equatorial regions.

Doug

Posted by: silylene Mar 25 2006, 06:23 PM

QUOTE (djellison @ Mar 25 2006, 05:20 PM) *
Let's go totally and utterly nuts - let's say the temperature increase is as much as 5 degrees ( I doubt it would be 1/10th of that)

You're only raising things to a temperature they would have exceeded, regularly, for prolonged periods, all summer. If you're suggestion is that wheel friction is causing an increase in temperature of a few degrees, thus melting ice content of the soil, then that same ice would have been melted just by the warmer temperature of the summer, for hundreds of sols, across the whole planets equatorial regions.

Doug


I agree, Doug.

Posted by: Steve Mar 25 2006, 06:30 PM

QUOTE (RGClark @ Mar 25 2006, 11:41 AM) *
I had suggested that one method to observe indications of moisture by the rovers would be to cover an area at night (to preserve deposited frost/ice) and uncover it in the morning:

In fact, they've been incidentally doing that for some time by leaving the instruments in contact with the soil for overnight measurements.
This image from SOL 65, a day which Spirit spent "analyzing soil targets with the alpha particle x-ray spectrometer, Mössbauer spectrometer and microscopic imager," suggests that some interesting surface changes took place.

Whether that smooth white surface is due to mere compaction by pressure or to water vapor or chemical transport I leave to people who got further along in chemistry than I ever did. I presume the Mössbauer and APXS results from SOL 65 are available by now for those who are interested.

Posted by: Marcel Mar 25 2006, 07:17 PM

Moving a wheel through talcum powder (which has probably far larger grains compared to this stuff) is not going to get you any heat worth talking about.

Theoretically, yes: The grains collide, so frictional heat must be generated. Theoretically yes: there's interstitial water in the salts, so this can be liberated by this "destruction".

Practically, no: I bet we're talking several molecules here. Not an amount that is detectable at all !

Besides, the only situation that (to my opinion) can generate heat with respect to the stalled wheel is when scrapping it along bedrock. Very localized for a very short period of time....

Posted by: RGClark Mar 25 2006, 08:01 PM

QUOTE (Marcel @ Mar 25 2006, 07:17 PM) *
Moving a wheel through talcum powder (which has probably far larger grains compared to this stuff) is not going to get you any heat worth talking about.

Theoretically, yes: The grains collide, so frictional heat must be generated. Theoretically yes: there's interstitial water in the salts, so this can be liberated by this "destruction".
...



At this point, I don't believe the presence of the ice/frost is theoretical anymore. All the current landers and orbiters confirm it is there.
We can debate about the accuracy of the model. In any case I believe that daytime temperatures alone with the presence of salts are sufficient to melt this ice seasonally.


Bob Clark

Posted by: djellison Mar 25 2006, 08:53 PM

QUOTE (RGClark @ Mar 25 2006, 08:01 PM) *
I believe that daytime temperatures alone with the presence of salts are sufficient to melt this ice seasonally.


So where are the lakes, bogs, the mud, to put it bluntly - the evidence for it?

Because this isnt it - this is just dry dust being dragged through.

And why do all the leading authorities on Mars disagree with you? What astonishing revelation have you discovered which they have overlooked?

ODug

Posted by: Myran Mar 25 2006, 08:59 PM

Yes we have seen frost at the Viking landing site, and its not at all unlikely that there have been some frost at the cryogenically cold nights the rovers might have experienced.
So far I am able to go with you RGClark, but that frost comes from the atmosphere in the first place.

The wheels might be a few degrees warmer than the environment, which means they still are somewhere 30-60 degrees colder than the melting point of water.

Secondly: Its one thing to feel frictional heat when you rub the palm of your hand against the textiles of your own pants for example, but it would take a calorimeter to even detect the extemely small fricitonal heat of wheels moving at centimeter speeds.

Posted by: RGClark Mar 26 2006, 12:25 AM

QUOTE (djellison @ Mar 25 2006, 08:53 PM) *
So where are the lakes, bogs, the mud, to put it bluntly - the evidence for it?

Because this isnt it - this is just dry dust being dragged through.

And why do all the leading authorities on Mars disagree with you? What astonishing revelation have you discovered which they have overlooked?

ODug


I'm referring to the micron scale ice/frost deposition that all the current Mars craft have shown exists even at near equatorial latitudes. The reports showing this are cited in the sci.astro posts I mentioned above.
Some of these reports show some of the deposition occurs during the local Summer season. Daytime temperatures are known to exceed the melting point of water near the equator during this season.
I would be interested to know what the authors of these reports say happens to this water during Summer daytime hours especially considering the presence salts/sulfates widespread on Mars.


Bob Clark

Posted by: Marcel Mar 26 2006, 11:54 AM

QUOTE (RGClark @ Mar 25 2006, 08:01 PM) *
At this point, I don't believe the presence of the ice/frost is theoretical anymore. All the current landers and orbiters confirm it is there.
Bob Clark

I never said that. I said practically no water will be freed this way. Some molecules maybe, but that's no water to me. It's nothing.

Posted by: RGClark Mar 26 2006, 01:31 PM

QUOTE (Marcel @ Mar 26 2006, 11:54 AM) *
I never said that. I said practically no water will be freed this way. Some molecules maybe, but that's no water to me. It's nothing.


If it was enough to be visible on the MER rover as frost, it's more than nothing.
If this were liquified for example it would be enough to supply microbes with sufficient water to survive on.
I'm arguing that since the abundant salts known to be present lower both the temperature and pressure requirements for liquid water, it can and does become liquified seasonally on Mars.


Bob Clark

Posted by: CosmicRocker Mar 27 2006, 05:03 AM

QUOTE (RGClark @ Mar 25 2006, 09:52 AM) *
In discussions on the internet one should always endeavor to maintain civility in your discussions.
Bob: Just how was I not being civil when I posed that question to you? I thought I was simply asking an obvious question. blink.gif

Posted by: TheChemist Mar 27 2006, 12:04 PM

QUOTE (CosmicRocker @ Mar 27 2006, 08:03 AM) *
Bob: Just how was I not being civil when I posed that question to you? I thought I was simply asking an obvious question. blink.gif


I think Bob just acknowledges that the subsequent use of bold capitals in his own reply is not civil smile.gif

Posted by: Bob Shaw Mar 27 2006, 12:57 PM

Let me summarise.

So far as I know, in the depths of Hellas there's enough atmospheric pressure to allow liquid water to briefly exist, though not to persist as it'd quickly evaporate; things are not so easy where the MERs are. Temperatures on Mars certainly *do* reach above the freezing point of pure water, and are often above that of salty water. Frost and snow were observed from the surface by Viking 2, and certain duricrust features observed by Viking implied the transport of water at least at molecular levels. Valles Marineris is often obscured by morning ground fogs made of water. Oh, and as for the polar caps and the sub arctic regions of Mars...

Any disagreements so far?

Now, add that catalogue of pretty well undisputed facts to the recent MER observations at Gusev. Frost *is* present; salty soils *are* present. There's the odd bit of cirrus in the sky.

We *have* seen strange flow features in numerous locations at Gusev, and they *could* be mediated by water. But, we can't tell much more than that at present, though there are certainly a few mechanisms which might make for some very interesting outcomes. And even if the mechanisms don't work today, they may have worked at some point in the past when the pressure of the atmosphere was not quite so low as we see today, and be preserved as a f*ssil record.

So where's the debate?

Well, we can argue about specifics, true. But the generalities? Nope!

Bob Shaw

Posted by: RGClark Mar 27 2006, 12:58 PM

QUOTE (CosmicRocker @ Mar 27 2006, 05:03 AM) *
Bob: Just how was I not being civil when I posed that question to you? I thought I was simply asking an obvious question. blink.gif



As Chemist said, I wasn't saying you were being uncivil. On the internet putting something in bold caps is analogous to yelling. My apologies.
I was being rather annoyed that my repeated citations of the reports of deposited water/ice at near equatorial latitudes were being ignored. I am arguing that since daytime temperatures can exceed the melting point at these latitudes and the known presence of salts decreases the temperature and pressure requirements for liquid water, this overwhelmingly implies liquid water brines form seasonally on Mars.
Such liquid water even if at layers at the micron-scale is enough for microbes to survive on.
This would be consistent with the origin of the detected methane being at near equatorial latitudes.


Bob Clark

Posted by: djellison Mar 27 2006, 01:31 PM

QUOTE (RGClark @ Mar 27 2006, 12:58 PM) *
Such liquid water even if at layers at the micron-scale is enough for...


But not enough to make mud, which is where your argument begins, and I still don't buy, for one minute, that the drag of a wheel would cause an noticeable increase in temperature.


Doug

Posted by: RGClark Mar 27 2006, 01:52 PM

QUOTE (djellison @ Mar 27 2006, 01:31 PM) *
But not enough to make mud, which is where your argument begins.

Doug



Mud or clays. Recall MER team members have argued APXS measurements of some Gusev rocks are best matched by clays.
Water vapor diffuses through porous soil. This subsurface water vapor may condense to ice. Being subsurface, it could be protected from subsequent evaporation/sublimation. Then over several days the amount of ice could be equivalent to millimeters of water.
The scraping away of the surface material by the wheels or by the airbags could expose this ice to the Sun. This with the additional heat produced by the dragging may have been enough to melt this ice.


Bob Clark

Posted by: Ames Mar 27 2006, 01:53 PM

QUOTE (djellison @ Mar 27 2006, 02:31 PM) *
But not enough to make mud, which is where your argument begins, and I still don't buy, for one minute, that the drag of a wheel would cause an noticeable increase in temperature.
Doug


Ahh but what about pressure?

Skiiers/Snow Boarders/Skaters all ride on a layer of water even when the snow/ice temperature is a long way below zero C.
It is pressure that melts a very thin layer of ice/snow.

Not saying that I agree with the mud theory, but that is it more than temperature.

Nick

Posted by: chris Mar 27 2006, 02:08 PM

QUOTE (Ames @ Mar 27 2006, 02:53 PM) *
Ahh but what about pressure?

Skiiers/Snow Boarders/Skaters all ride on a layer of water even when the snow/ice temperature is a long way below zero C.
It is pressure that melts a very thin layer of ice/snow.

Not saying that I agree with the mud theory, but that is it more than temperature.

Nick


We've done this already smile.gif

The rovers move very slowly, in 1/3 of our gravity. It isn't comparable to a dude on a snowboard.

For what its worth, I have always seen the "mud" as being very very fine dust.

Chris

Posted by: djellison Mar 27 2006, 02:26 PM

QUOTE (RGClark @ Mar 27 2006, 01:52 PM) *
additional heat produced by the dragging


I still maintain you're arguing a point that simply would not exist. At best, you would increase the temperature by an ammount significantly less than the day-night swing, and significantly less than seasonal swing. If mud like formations ( which is what you're saying this dragging has produces, soil with liquid water to produce that formation is your point ) can be triggered by the tiny tiny influence of a dragged wheel - then there should be HUGE ammounts of evidence of this all OVER the planet. Where is it?

Where's the pond in the bottom of the trenches that have been dug - you might get an increase in temperature there, of..ooo...a degree maybe? You're churning a lot of subsurface soil there, exposing it to the sun. Where are your mud and clays there? Where's the mud clinging to the wheels which have dragged their way thru km's of soil? Water vapour in the soil - that's great, but the total column volume of water in the atmosphere is about 20 microns.

Doug

Posted by: Bill Harris Mar 27 2006, 03:21 PM

QUOTE
Water vapor diffuses through porous soil. This subsurface water vapor may condense to ice. Being subsurface, it could be protected from subsequent evaporation/sublimation. Then over several days the amount of ice could be equivalent to millimeters of water. The scraping away of the surface material by the wheels or by the airbags could expose this ice to the Sun. This with the additional heat produced by the dragging may have been enough to melt this ice.


Evidence, please. All sorts of things _could_ happen but on a science board we are interested in what _can_ happen. Water does exist on Mars and can condense as frost and water-related weathering _has_ occurred.

--Bill

Posted by: RGClark Mar 27 2006, 03:25 PM

QUOTE (djellison @ Mar 27 2006, 02:26 PM) *
I still maintain you're arguing a point that simply would not exist. At best, you would increase the temperature by an ammount significantly less than the day-night swing, and significantly less than seasonal swing. If mud like formations ( which is what you're saying this dragging has produces, soil with liquid water to produce that formation is your point ) can be triggered by the tiny tiny influence of a dragged wheel - then there should be HUGE ammounts of evidence of this all OVER the planet. Where is it?

Where's the pond in the bottom of the trenches that have been dug - you might get an increase in temperature there, of..ooo...a degree maybe? You're churning a lot of subsurface soil there, exposing it to the sun. Where are your mud and clays there? Where's the mud clinging to the wheels which have dragged their way thru km's of soil? Water vapour in the soil - that's great, but the total column volume of water in the atmosphere is about 20 microns.

Doug


The amount of ice in the soil can be higher than 20 microns if it is replenished daily subsurface and it is protected from evaporation by remaining covered.
I am saying this ice exists planet-wide and moreover this melting occurs over a large portion of the planet, mostly in the temperate zones. My key over-arching point is that this melting has been confirmed by the current orbiters observations of seasonal varyings in the bound water content of hydrated minerals (reported in the articles I cited in my sci.astro post.)
I'm arguing that these hydrated minerals form by liquid water on Mars as they do on Earth.
Whether or not the wheel dragging itself causes further melting of subsurface water is not a big deal.
Solar illumination itself I argue is enough to melt surface frosts with the addition of the known presence of salts.



- Bob Clark

Posted by: djellison Mar 27 2006, 03:27 PM

We know the ice exists all over the planet - GRS telles us that, in quantites from not a lot - to huge ammounts.

What you are saying is that this regularly becomes liquid.

Where are the lakes, rivers, ponds, bogs, mud slides, streams?

If sub-surface water were becoming liquid regularly, then where is it? Where did it come from? What's pushing it to the surface?

You're trying to impose vast quantites of 'if' 'might' and 'may' onto some dragged tracks that look, at first glance with earth-bound eyes, a bit like mud.

QUOTE (Bill Harris @ Mar 27 2006, 03:21 PM) *
Evidence, please.


Exactly.

Doug

Posted by: silylene Mar 27 2006, 03:32 PM

QUOTE (Ames @ Mar 27 2006, 01:53 PM) *
Ahh but what about pressure?

Skiiers/Snow Boarders/Skaters all ride on a layer of water even when the snow/ice temperature is a long way below zero C.
It is pressure that melts a very thin layer of ice/snow.
...

Nick


This is incorrect and old tale often repeated, but unfortunately, wrong.

The slipperiness of ice and snow is not the result of pressure melting. Pressure melting does not occur to a useful extent even with ice skating (where the pressure/area is much greater than a ski or snowboard) once the temperature falls below -8C. Please read the Physics Today article: http://www.geo.hunter.cuny.edu/~hsalmun/ice_phy2day.pdf

Posted by: silylene Mar 27 2006, 03:54 PM

QUOTE (RGClark @ Mar 27 2006, 03:25 PM) *
The amount of ice in the soil can be higher than 20 microns if it is replenished daily subsurface and it is protected from evaporation by remaining covered.
I am saying this ice exists planet-wide and moreover this melting occurs over a large portion of the planet, mostly in the temperate zones. My key over-arching point is that this melting has been confirmed by the current orbiters observations of seasonal varyings in the bound water content of hydrated minerals (reported in the articles I cited in my sci.astro post.)


- Bob Clark


Melting has not been confirmed in the wheel trenches, which is what we are discussing.

QUOTE
Whether or not the wheel dragging itself causes further melting of subsurface water is not a big deal.


Ok, we can drop the wheel dragging friction or compression causing melting from discussion.

QUOTE
Solar illumination itself I argue is enough to melt surface frosts with the addition of the known presence of salts.


OK let's discuss solar warming of putative surface or subsurface frosts exposed in wheel-opened trenches as a mechanism for mud formation.

Assuming thin subsurface frosts exists, perhaps sublimation is more likely than melting once such frosts are exposed to sunlight. Unfortunately, we lack data, since most (all?) of the brine evaporation/sublimation experiments did not use a suphurous brine, rather they used alkali metal-halide brines. There will be differences in the evaporative properties when anions with -2 charge are present (probably helpful to your hypothesis).

Assuming melting (not sublimation occurs) from the putative surface and subsurface frosts, whether it can form a mud before the liquid water evaporates becomes a chemistry kinetics issue. Here are some questions (data) needed before making a claim of mud:
-1. How fast will briney water(l) be formed by solar warming compared to how fast it evaporates?
-2. Assuming the amount of frost is x% of the soil, what is the maximum amount of water formed in #1?
-3. How long would it take (seconds) for #2 (maximum amount of water)?
-4. Is there sufficient quantity of water (#2) to wet y grams of dehydrated soil dusts within z seconds (#3) before the putative water evaporates?
-5. Is there enough time within the brief period of time that the wheel opens and spreads the soils to actually make a mud (time required as defined in #4)?

Posted by: Ames Mar 27 2006, 04:20 PM

QUOTE (silylene @ Mar 27 2006, 04:32 PM) *
This is incorrect and old tale often repeated, but unfortunately, wrong.

The slipperiness of ice and snow is not the result of pressure melting. Pressure melting does not occur to a useful extent even with ice skating (where the pressure/area is much greater than a ski or snowboard) once the temperature falls below -8C. Please read the Physics Today article: http://www.geo.hunter.cuny.edu/~hsalmun/ice_phy2day.pdf


Very interesting - Thanks for pointing this out.

To be more precise Pressure melting is not the whole story - as with most things "it's not as simple as you think"

To quote from Physics Today "Each mechanism [Pressure Melting, Frictional Melting and Liquid-like films] plays a role that depends on temperature."

I shall endeavour to be more rigorous in the future. wink.gif

Nick

Posted by: RGClark Mar 27 2006, 05:26 PM

QUOTE (djellison @ Mar 27 2006, 03:27 PM) *
We know the ice exists all over the planet - GRS telles us that, in quantites from not a lot - to huge ammounts.

What you are saying is that this regularly becomes liquid.

Where are the lakes, rivers, ponds, bogs, mud slides, streams?

If sub-surface water were becoming liquid regularly, then where is it? Where did it come from? What's pushing it to the surface?

You're trying to impose vast quantites of 'if' 'might' and 'may' onto some dragged tracks that look, at first glance with earth-bound eyes, a bit like mud.



Exactly.

Doug

Well, we have seen examples of recent "streams", ephemeral they may have been. It's the Malin-Edgett gullies I mean. And the latest announcement is that such gullies are currently forming. I argue these currently forming gullies are also from liquid water.
As for ponds, I'm going to make a prediction that MRO will find small ponds located on Mars, oases if you will. These will be analogous to Don Juan pond in Antarctica.
My guess for where they will be found is at near equatorial areas that are known to have low lying fogs or clouds:

Clouds in Noctis Labyrinthis on Mars.
http://www.photovault.com/Link/Universe/Planets/Mars/UPMVolume01/UPMV01P02_06NoctisLabyr.html

As for lakes, I believe they do exist currently on Mars though subice, like the subice lakes in Antarctica. However, I don't know if MRO will have sufficient sensitivity to detect them.



Bob Clark

Posted by: general Mar 29 2006, 08:04 AM

Struggling a bit... huh.gif sad.gif

http://qt.exploratorium.edu/mars/spirit/forward_hazcam/2006-03-28/2F196854911EFFAQE2P1211R0M1.JPG
http://qt.exploratorium.edu/mars/spirit/rear_hazcam/2006-03-28/2R196674862EFFAQBMP1301R0M1.JPG

Posted by: Sunspot Mar 29 2006, 08:44 AM

QUOTE (general @ Mar 29 2006, 09:04 AM) *
Struggling a bit... huh.gif sad.gif

http://qt.exploratorium.edu/mars/spirit/forward_hazcam/2006-03-28/2F196854911EFFAQE2P1211R0M1.JPG
http://qt.exploratorium.edu/mars/spirit/rear_hazcam/2006-03-28/2R196674862EFFAQBMP1301R0M1.JPG


Oh Dear. Things are not looking good for Spirit at all. I didn't expect this wheel problem to be quite so crippling after the progress they previously made on 5 wheels.

Posted by: djellison Mar 29 2006, 08:44 AM

QUOTE (RGClark @ Mar 27 2006, 05:26 PM) *
As for ponds, I'm going to make a prediction that MRO will find small ponds located on Mars, oases if you will. These will be analogous to Don Juan pond in Antarctica.


Of course, the genius of that argument is that you can always say "well - it's not found them YET...but it will" for about 10 years smile.gif They'd have to be very very very small ponds to be visible with HiRISE but not with MOC, and MOC's been looking at Mars for nearly a decade.

Someone elsehwere has branded me as being 'anti' water. ( and I know they're reading - why not join in and make your case? ) and that's simply untrue. Think of the astonishing implications w.r.t astrobiology if we were to find liquid water on the surfafe of Mars. The impact would be huge, and it would be brilliant for exploration. Why would anyone so enthusiastic about space exploration as I be opposed to such a thing?

However - I'm pro-evidence - and I'm yet to see any evidence of water here.

Doug

Posted by: edstrick Mar 29 2006, 12:16 PM

Dealing with full time work and nearly full time elder-care, I have not been able to go down to the Univ. Texas. libraries, borrow the technical literature published by the Odyssey Gamma and Neutron instrument teams, xerox (lower case ;-> ) them and READ them. So I'm working from background knowledge here.

But regarding low latitude *HYDROGEN* on Mars. Note that we have no direct evidence for on-surface or subsurface water at low latitudes on Mars AT ALL. We did see water ice (presumably and most plausibly) on the top of Oppy's deck and or solar panels one near-dawn morning, deposited from the chilled atmospheric boundary layer pre-dawn. I do not know what current thermal modeling of the top surfaces of Oppy at that time of year with the Mini-TES measured atmosphere opacity and temperatures, or the modeled near-dawn boundary layer temperature of the atmosphere was. But that's it.

We DO see diurnal ice-hazes and fogs, some clearly trapped in topographic lows like craters and valleys, but there is little indications that this ice is deposited on the surface in anything more than trace and very transient amounts.

<to be continued next post>

Posted by: edstrick Mar 29 2006, 12:43 PM

What DO we see in the Odyssey orbital data? We see indications of a small but decidedly non-zero amount of hydrogen in the low latitude martian surface. We see it with horribly low resolution: We can map gross regional variations but not local correlations with discrete topographic features and color/albedo/thermal soil units. We reportedly see seasonal variations in hydrogen/water low latitude regions on the order of a few percent. How accurate either the absolute abundance and variability measurements are, I do NOT know. Outside of high latitudes where signal-to-noise in the data are high, I do not know whether the modelling based on the different energy neutron data plus the gamma data indicates any depth variation of water content in the surface materials.

In addition, there are both statistical and systematic errors in the measurement. One cause of systematic errors may be the the seasonal atmospheric pressure variation on Mars. I know atmospheric attenuation is a problem with the gamma data, I don't know how much it may complicate the different energy neutron bands. The published maps are so smoothed I get very little idea what's noise and what's feature. Lunar neutron data showed systematic effects due to surface composition and raw maps based on that data could mindlessly be interpreted as "water" at low latitudes where it's not plausibly present. For Odyssey, I have not seen seasonal maps, nor seen any comparison between Year 1 and 2 seasons in 2002, 2004 and now (presumably not processed) 2006 Mars Year 3 data.

So what is it we see? Hydrogen. It may be ice. Certainly a significant amount of it is water of hydration in sulfate minerals. That is likely to be the vast majority of hydrogen/water in non-ice-bearing soils planetwide. Additional amounts of hydrogen may be present in clay minerals or as yet poorly defined (some may not really be definable minerals of definite composition) weathering products, as well as bound hydrogen in water in igneous rocks and minerals. Some hydrogen will be present as adsorbed water, trapped on and in the surfaces of mineral and mineraloid grains.

<more next post>

Posted by: abalone Mar 29 2006, 12:59 PM

While you guys are arguing over the "could be, shouldn't be" frost you have all taken your eyes off the ball. All I see is the wheel sinking deeper. Can it ever get out of here on five wheels?

Is the dream over?

Is this the final panorama?


 

Posted by: edstrick Mar 29 2006, 01:02 PM

Ultimately, we will need (among other things) an aerostationary orbiter instrumented for martian meteorology, and climatology. This is needed to complement time-zone limited data from sun synchronous polar orbiters.

Meteorology instruments can observe the full diurnal cycle of ice and dust hazes and clouds, as well as regular meteorological events like winter cold fronts and special events like regional and global dust storms.

We should also be able to directly observe full diurnal temperature curves for the surface and infer sub-surface thermal layering to a depth of a centimeter in low thermal inertia regions like Arabia to centimeters in high inertia regions like Meridiani Sinus. We should also be able to directly observe post sunrise and pre-sunset albedo changes of the surface in the visible and near infrared and and set solid limits on frost deposition and hydration changes in sunlit surface minerals.

Note that temperatures where it's easy to have ultra-saline brines stable at Martian surface pressures tend to be present in only the very very uppermost layers of the surface. The "thermal skin depth" of the martian surface is one or two centimeters in low inertia regions, maybe 5 or 8 centimeters (I'd have to dig into literature on Viking IRTM observation modeling to get the exact numbers) At a depth of 1 thermal skin depth, the diurnal temperature variation is sharply reduced, I think to 1/e the variation at the surface or something similar to that. A very few thermal skin depths below the surface, the temperature variation is only a few degrees or so. Because this is a diffusion process, mathematically, the seasonal skin depth is only a few times deeper than the diurnal depth. At maybe a meter depth, there's almost no temperature variation year-round.

Low inertia materials, like those in Arabia, seem to require surface material with physical properties like unconsolidated cement powder. High inertia materials seem to require sand. Some very high inertia regions imply somewhat cemented sand or coarse sand to granule dominated surface material. Rock abundances are generally low but can be estimated in the multi-spectral thermal data and are near-zero (few percent or less) in low inertia regions and many percent to some 15% in higher inertia regions. Rocks can be partially dusted bedrock, loose cobbles and rocks, or highly cemented materials.

Most materials the rovers excavate seem to behave as dry powders, some granules, some coarse to fine sand, some silt to clay sized particles, sorted or mixed in varying amounts. Some gives the appearance of "mud", but the proponents of these materials being mud have to provide evidence that clay-sized or clay and silt-sized powders can NOT explain the mechanical behaviour and appearance of the seemingly wet soils.

Enough ramblings for tonight. I'll sort some more of this out later.

Posted by: djellison Mar 29 2006, 01:27 PM

Good grief, one high-slip drive, and people are calling it the end of Spirit - for all we know there may have been some cunning engineering exercise going on.

I'd have thought after nearly 800 sols, we'd have all learnt to be a bit more patient than that.

Doug

Posted by: Tesheiner Mar 29 2006, 01:42 PM

Engineering exercises aside, it looks Spirit is making a right turn probably (imho) looking for a less sandy path to the hills.

Posted by: brianc Mar 29 2006, 02:28 PM

Could I suggest a new thread entitled 'Handbags at 10 paces' for this one ladies !

Posted by: RGClark Mar 29 2006, 04:07 PM

QUOTE (djellison @ Mar 29 2006, 08:44 AM) *
Of course, the genius of that argument is that you can always say "well - it's not found them YET...but it will" for about 10 years smile.gif They'd have to be very very very small ponds to be visible with HiRISE but not with MOC, and MOC's been looking at Mars for nearly a decade.

Someone elsehwere has branded me as being 'anti' water. ( and I know they're reading - why not join in and make your case? ) and that's simply untrue. Think of the astonishing implications w.r.t astrobiology if we were to find liquid water on the surfafe of Mars. The impact would be huge, and it would be brilliant for exploration. Why would anyone so enthusiastic about space exploration as I be opposed to such a thing?

However - I'm pro-evidence - and I'm yet to see any evidence of water here.

Doug


I agree there is not overwhelming visual evidence. But I'm also considering the evidence of the scientific instruments on the orbiters. The evidence from the instruments on the orbiters for frost/ice deposition even at near equatorial latitudes is overwhelming. Furthemore this frost has been actually seen by the Opportunity landers.
For a long time Mars scientists said in regard to liquid water on Mars that temperatures near the equator exceed the melting point, BUT, they said, the near equatorial latitudes are desiccated. Well, when you find these seasonally warm locations are NOT desiccated you don't just ignore that fact. You face squarely the implications for liquid water.
Actually I thought I was going out on a limb by predicting ponds to be discovered by MRO and even likely locations. Incidently I forgot to mention as well the upper latitudes of the Hellas basin as a likely location, since it also has frequent low lying fogs or clouds. Note that the frost deposition on Opportunity was observed in connection with clouds over the site. The fogs/clouds seen over Noctis are much denser and closer to the surface. Indeed they look more like cumulus clouds than thin cirrus clouds, which is why I'm suggesting visible surface ponds with better resolution imaging. To be precise, I'm predicting such ponds will be seen during the period such low, dense fogs are seen over these near equatorial locations.
I believe that such ponds have been seen by MGS, but they have been hard to prove at the resolution of MGS. I'm suggesting they will be proven by MRO. Note that the gullies were not discovered by Viking orbiter imaging, but the fact that THEMIS on Mars Odyssey has been able to detect them at similar resolution to the Viking orbiter resolution suggests they were visible by Viking, just not provably so.
With each factor of 10 improvement of visual resolution of Mars has come revolutionary changes in our understanding of the role of liquid water on Mars. What revolutionary improvement over the discovery of possibly currently forming gullies by MGS would you predict for MRO?



Bob Clark

Posted by: djellison Mar 29 2006, 04:59 PM

QUOTE (RGClark @ Mar 29 2006, 04:07 PM) *
The evidence from the instruments on the orbiters for frost/ice deposition even at near equatorial latitudes is overwhelming.


Really? Hydrogen, yes - but one can only infer that to be ice. Phoenix should help us there and indeed it probably IS ice making up the percentage mass that those maps show us - but that doesnt actually provide evidence for the surface liquid water your claim there to be any more than the frost inside my freezer proves that there is a cup of liquid water sat in it.

QUOTE
Furthemore this frost has been actually seen by the Opportunity landers.


Yes - 3 hrs later it was gone, leaving no trace of ever having existed. It didnt form puddles on the rover, it sublimed back into the atmosphere. It really doesnt provide anything for your case.

QUOTE
To be precise I'm predicting such ponds will be seen during the period such low, dense fogs are seen over these near equatorial locations.

Through the fog? Are you predicting open water will. Given that the atmosphere is 100% humid as it is, one presumes that these ponds would struggle to evaporate away, so what would your prediction on how these form, their logevity, and how they vanish - and how do you side your prediction of only very small ponds ( fortuitously unobserveable with any instrument to date ) and nothing larger that would have been detected by one of the 3 spacecraft currently studying the planet.

QUOTE
What revolutionary improvement over the discovery of possibly currently forming gullies by MGS would you predict for MRO?


I wouldnt be so bold as to predict what might be 'discovered'. That's the whole basis of discovery - you discover things. Perhaps there are short lived outbursts of water causing these features. Perhaps they're caused by landslides, perhaps they're something we don't even know yet. And hopefully, MRO will get a good high res view of these and we'll be able to see what might cause them with a little more details. There's still an open virdict on the origin of them as it is
http://www.space.com/scienceastronomy/060321_mars_water.html
http://spacenews.dancebeat.info/article.php/mars-gullies-could-form-without-water

I'd like to see your MGS MOC obs of ponds ( and I know that sounds sarcastic, but it's not meant to be ) - because I'm fairly sure that if there were such obvious evidence of ponds on the surface of Mars - something would have been announced.

Like I said earlier - I'm not overse to the idea of surface liquid water on Mars, it would make it a more attractive place for exploration, but to date we have no evidence of it.

Doug

Posted by: RGClark Mar 29 2006, 07:56 PM

QUOTE (djellison @ Mar 29 2006, 04:59 PM) *
...
I'd like to see your MGS MOC obs of ponds ( and I know that sounds sarcastic, but it's not meant to be ) - because I'm fairly sure that if there were such obvious evidence of ponds on the surface of Mars - something would have been announced.

Like I said earlier - I'm not overse to the idea of surface liquid water on Mars, it would make it a more attractive place for exploration, but to date we have no evidence of it.

Doug


Here's one observed early in the MGS mission.

MOC--The First Year--Top 10
Water: Seepage and Ponding
Mars Global Surveyor Mars Orbiter Camera Release: MOC2-74
Mars Global Surveyor Mars Orbiter Camera Image ID: 567897575.7707
P077-07
http://www.msss.com/mars_images/moc/top102_Dec98_rel/seepage/

As I said this couldn't be proven to have been liquid. But it is interesting it was observed in connection with the Malin-Edgett gullies.


Bob Clark

Posted by: djellison Mar 29 2006, 08:01 PM

Well put by MSSS I think

It is important to note that both the channel and floor relationships seen in this image may be formed by other processes, and that there is also the possibility that they may not be related (i.e., that the fluid from the channels did not emplace the dark, ponded floor material). It is also important to remember that a fluid other than water, for example, fluid lava, could be responsible for the features seen. Indeed, lower resolution Viking and some MOC images suggest just such an alternative explanation. The absence of craters may reflect the difficulty of the materials to preserve such features, or their burial by dust. Finally, the environmental difficulties of having liquid water seeping from the wall of a south polar crater are quite formidable. For these reasons, caution must be exercised in adopting any specific hypothesis.

Posted by: Bubbinski Mar 29 2006, 09:24 PM

I'm wondering what the latest word on the wheel is....have they found any avenues of hope, anything else to try to get it unstuck? Or have they given up on the wheel?

Also are they still optimistic about getting the rover to a higher ground/north facing slope in time? Is the power situation stable for now?

Posted by: djellison Mar 29 2006, 11:08 PM

I think they've given up until they get to some nice slopes - then they can spend some time doing more engineering experiments on it - but it does look fairly terminal

Doug

Posted by: Bubbinski Mar 30 2006, 12:04 AM

Thanks Doug...hopefully it still looks good for getting to the north slopes.

Posted by: Shaka Mar 30 2006, 05:12 AM

QUOTE (Bubbinski @ Mar 29 2006, 02:04 PM) *
Thanks Doug...hopefully it still looks good for getting to the north slopes.

Oh yeah, Bubba! Hope is all we got, good buddy. But it ain't like we wuz flyin' to our Sacred Refuge.
No, me. Flyin' ain't the word.
Time t=0: http://marsrovers.jpl.nasa.gov/gallery/all/2/n/787/2N196232587EFFAQAEP1910R0M1.JPG
Time t=0+8.17 earth days: http://qt.exploratorium.edu/mars/spirit/navcam/2006-03-29/2N196939101EFFAQE2P1722L0M1.JPG
Flyin' ain't the word. sad.gif

Posted by: RGClark Mar 30 2006, 08:21 AM

QUOTE (edstrick @ Mar 29 2006, 12:16 PM) *
Dealing with full time work and nearly full time elder-care, I have not been able to go down to the Univ. Texas. libraries, borrow the technical literature published by the Odyssey Gamma and Neutron instrument teams, xerox (lower case ;-> ) them and READ them. So I'm working from background knowledge here.

But regarding low latitude *HYDROGEN* on Mars. Note that we have no direct evidence for on-surface or subsurface water at low latitudes on Mars AT ALL. We did see water ice (presumably and most plausibly) on the top of Oppy's deck and or solar panels one near-dawn morning, deposited from the chilled atmospheric boundary layer pre-dawn. I do not know what current thermal modeling of the top surfaces of Oppy at that time of year with the Mini-TES measured atmosphere opacity and temperatures, or the modeled near-dawn boundary layer temperature of the atmosphere was. But that's it.

We DO see diurnal ice-hazes and fogs, some clearly trapped in topographic lows like craters and valleys, but there is little indications that this ice is deposited on the surface in anything more than trace and very transient amounts.

<to be continued next post>


The reports on the detection of seasonally variable water content (bound or free water/ice) at near equatorial sites by the MER rovers, by MGS, and by Mars Odyssey are cited in the sci.astro post copied below.
The detection of variable water content by Mars Express is discussed here:

OBSERVATION OF 3 μm HYDRATION FEATURE ON MARS FROM OMEGA-MEx DATA.
D. Jouglet, F. Poulet, J. Mustard, R. Milliken, J.P. Bibring, Y. Langevin, B. Gondet and the OMEGA team.
1IAS, Université Paris 11, 91405 Orsay Cedex, France, denis.jouglet@ias.u-psud.fr. Brown University,
Providence, USA.
Lunar and Planetary Science XXXVII (2006) 1741.pdf
http://www.lpi.usra.edu/meetings/lpsc2006/pdf/1741.pdf

One of the locations in this report showing variable water content is Marwth Vallis. At 25 N latitude, I consider this a near equatorial site. In any case the maximum daytime temperature here exceeds the melting point of water seasonally.
Mawrth Vallis was one of the locations shown to contain clays. The authors of this report suggest the variable water could be free water/ice absorbed on these clays instead of bound water. I therefore wonder if the seasonally variable water content seen by the MER rovers and by MGS could also be due to absorbed free water.


Bob Clark

**************************************************************
From: Robert Clark
Date: Sat, Feb 11 2006 9:32 pm
Email: "Robert Clark" <rgregorycl...@yahoo.com>
Groups: sci.astro, alt.sci.planetary, sci.physics, sci.geo.mineralogy
Subject: Re: Could We Make A "Solar Still" On Mars?

The following reports to be presented to the 2006 Lunar and Planetary
Science Conference discuss seasonal variations in the bound water
content even at near equatorial latitudes:

SPATIAL AND TEMPORAL VARIATIONS OF BOUND WATER CONTENT IN THE MARTIAN
SOIL WITHIN THE GUSEV CRATER: PRELIMINARY RESULTS OF THE TES AND
MINI-TES DATA ANALYSIS.
R. O. Kuzmin1, P. R. Christensen2, S. W. Ruff2, T. G. Graff2, A. T.
Knudson2, M. Yu. Zolotov2, Athena Science Team, 1Vernadsky Institute of
Geochemistry and Analytical Chemistry, Russian Academy of Sciences, 19
Kosygin str., Moscow 119991, Russia, e-mail: *...@geokhi.ru,
2Department of Geological Sciences, Arizona State University, Tempe, AZ
85287, USA.
http://www.lpi.usra.edu/meetings/lpsc2006/pdf/1673.pdf

MAPPING OF SEASONAL BOUND WATER CONTENT VARIATIONS ON THE MARTIAN
SURFACE BASED ON THE TES DATA.
R. O. Kuzmin1, P. R. Christensen2, M. Yu. Zolotov2 and S. Anwar2.
1Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian
Academy of Sciences, 19 Kosygin str., Moscow
119991, Russia, e-mail: *...@geokhi.ru, 2Department of Geological
Sciences, Arizona State University, Tempe, AZ
85287.
http://www.lpi.usra.edu/meetings/lpsc2006/pdf/1846.pdf

This confirms observations of the HEND instrument on Mars Odyssey of
seasonal variations in the deposited water/ice content of the soil.
Note that this strongly implies the varying bound water is due to this
seasonal water deposition.
One type of mineral found containing the bound water is carbonate. Then
this carbonate should arise from this seasonal deposition. Most
importantly this implies this carbonate is currently forming.
One small discrepancy in the bound water observations and the HEND
measurements is that HEND suggests that in the south, the greatest
deposition occurs in the southern Summer, while the bound water
measurements show the largest amount of bound water is observed in the
southern Winter.
A possible explanation is based on the idea that the currently forming
bound water minerals are formed from liquid water brines. Since these
latitudes are near the equator, mid-day temperatures could be within
the range of liquid water brines even during Winter.
However, the Summer daytime temperatures may be too high to permit the
water to remain liquid for long before evaporating.
Evidence for this is that during southern Summer, clouds have been seen
by the Opportunity rover at night when the temperatures are low, while
the clouds and frosts have not been seen during the day. Since similar
clouds corresponded to observed frost deposition on the Opportunity
rover during the southern Winter, it is very likely water/ice
deposition occurred during the southern Summer as well, though at night
when the clouds appear.
I want to suggest that a search be made for this night-time deposition
by methods such as described in the post to sci.astro below.
Note experiments in simulated Mars conditions show that water can stay
liquid in brines for short times on Mars:

Water just might stay liquid on Mars
Studies show salty water can persist, raising hopes for life.
http://msnbc.msn.com/id/10052714/from/RL.2/

For this reason it very likely the currently forming carbonate on Mars
is formed from liquid water as it is on Earth.


Bob Clark


===========================================================
From: Robert Clark
Date: Thurs, Jan 19 2006 12:15 pm
Email: "Robert Clark" <rgregorycl...@yahoo.com>
Groups: sci.astro, alt.sci.planetary, sci.physics
Subject: Re: Could We Make A "Solar Still" On Mars?

There have been some video posted to the Unmannedspaceflight.com site
of these night-time clouds:

http://media.putfile.com/earthrise-oppy-sol-687

http://www.lyle.org/~markoff/op_movie/opp_687L1.gif

Do the fast bright streaks in the second video look like meteorite
trails?

I suggested the current deposition of the water/ice at Meridiani may
become liquid at some point because of the warm maximum temperatures
during the current Summer season. This is supported by the detection of
carbonate in dust by the rovers, and also from orbit:

January 09, 2004
Spirit Lowers Front Wheels, Looks Around in Infrared.
"We came looking for carbonates. We have them. We're going to chase
them," said Dr. Phil Christensen of Arizona State University, Tempe,
leader of the Mini-TES team. Previous infrared readings from Mars orbit
have revealed a low concentration of carbonates distributed globally.
Christensen has interpreted that as the result of dust interaction with
atmospheric water. First indications are that the carbonate
concentration near Spirit may be higher than the Mars global average."
http://marsrovers.nasa.gov/newsroom/pressreleases/20040109a.html

On Earth in nature carbonate is produced by iteraction with *liquid*
water. There have been some laboratory experiments that attempt to show
it can form with water vapor alone but this hasn't been seen in nature.
I suspect in fact in these experiments some small amounts of liquid
water are involved undetected by the experimenters.
It is quite key then that the HEND instrument on Mars Odyssey shows
water/ice deposition occurs on Mars even at near equatorial locations:

47 - EVIDENCE OF THE SEASONAL REDISTRIBUTION OF WATER
IN THE SURFICIAL MARTIAN REGOLITH BASED ON ANALYSIS OF
THE HEND MAPPING DATA.
R.O. Kuzmin, E.V. Zabalueva, I.G. Mitrofanov,
M.L.Litvak, A.V.
Parshukov, V.Yu.Grin'kov, W. Boynton, R.S. Saunders.
"As it well seen from fig.1b,c,d, two distinctive
"hollows" of neutrons flux reduction have been appeared
in the northern hemisphere during northern summer at
Ls=130°-170° and in first half of northern winter at
Ls=270°-330°, being extended from high to low
latitudes. At that, later "hollow" (Ls=270°-330°) is
characterized by much stronger reduction of the
neutrons flux and it traces from northern polar region
up to low latitudes in the southern hemisphere. The
first "hollow" is related with periods of the northern
middle summer, while the second one - with of the
southern middle summer. In both case the residual
polar caps serve as main source of the water in the
Martian atmosphere."
p. 2
http://www.geokhi.ru/~planetology/theses/47_kuzmin_et_al.pdf

This deposition was confirmed by Opportunity by the detection of frost
on the rover during the Winter season. But I consider it quite key here
that HEND shows the deposition is actually higher during the current
southern Summer season. So since maximal temperatures can exceed
melting currently, the carbonate may form in the period when
temperature is above melting but before it reaches the boiling point in
the low atmospheric pressure on Mars.
I therefore propose to search for this liquid water by the rovers.
However, I am informed that for technical reasons the rover engineers
prefer not to deploy the rover arm in the middle of the night. During
the current Summer season, the greatest deposition probably occurs at
night because of the colder temperatures. You want to cover the area
during the night to preserve this water before it burns off in the
daytime.
So some other methods: perhaps the RAT could be applied not in the
middle of the night but close to but just before sunrise. I don't know
if this would be sufficient to preserve the moisture. Another
possibility: move a small rock in the middle of the night to cover a
small area. Then uncover the area during the early morning, as soon as
light is available.
Another possibility: it may work to use a wheel to cover the area. This
would have to be done at night to insure the deposition has already
occurred. Then as soon as light comes, move the vehicle to uncover the
area. The problem is this might disturb the area so much to make the
moisture no longer visible.
Still another possibility: I remember reading the rover could move all
the wheels so that they all dug into the ground at the same time. Then
we could do that so that the bottom of the rover clung tightly to the
ground. Then move the rover to uncover this area at sunrise. A problem
with this is that if the rover bottom is this close to the ground it
may be difficult to extract the rover from this position.
Any others?


Bob Clark


Robert Clark wrote:
> Note we might already be seeing an example of this. See the MI images
> here:
> Erebus Outcrops.
> http://www.markcarey.com/cgi-bin/mt/mt-view.cgi/18/entry/27390/discussion_page?start=374&show=20
> The flattened areas have a mushy appearance to them. Another check for
> this might be to perform a RAT observation early in the morning where
> there might be residual moisture left and compare this to a RAT
> observation of a spot nearby later in the afternoon when moisture would
> be expected to burn off.
> Would there be a difference in the appearance in the two RATted areas?
> Bob Clark
> Robert Clark wrote:
> > Mars Odyssey hydrogen-content measurements have shown seasonal
> > deposition of water/ice on Mars even at equatorial locations. This has
> > been confirmed by the Opportunity rover in Meridiani by the observation
> > of early morning frost on the rover:
> > More on "Frost on the rover solar panels".
> > http://bautforum.com/showpost.php?p=323577&postcount=6
> > This deposition of frost at Meridiani corresponded to the observation
> > of clouds over the site during the local Winter:
> > Mars Rovers Spot Water-Clue Mineral, Frost, Clouds.
> > 13-Dec-2004
> > http://marsrovers.jpl.nasa.gov/gallery/press/opportunity/20041213a.html
> > Since clouds have also been seen over the site during the current
> > Summer season, I argue this should also correspond to water/ice
> > deposition currently at the Meridiani landing site:
> > Space Sciences
> > Summer clouds over Meridiani?
> > Posted by Robert Clark on 12/31/2005 6:56:40 PM
> > http://habitablezone.com/space/messages/409185.html
> > The "Mars Rovers Spot Water-Clue Mineral, Frost, Clouds" press release
> > showed the frost forming in early morning in the Winter season. The
> > image of the frost was taken 11 minutes after sunrise, and a subsequent
> > image showed the frost had burned off 3 hours later due to rising
> > temperatures.
> > Perhaps the clouds in the images in the current season appear at night
> > because of the coldness at night during this current Summer period.
> > Then we might expect the greatest water/ice deposition to also occur at
> > night.
> > Could the mini-TES detect H2O on the rover at night? Could we for
> > example compare the spectra at night to the morning spectra?
> > Another experiment I suggest to try would be to press down with the RAT
> > at night and keep the area covered till early morning. Then uncover the
> > area soon after sunrise to see if there are any remaining signs of
> > moisture.
> > This may have what occurred at the Gusev landing site with the Spirit
> > rover landing bags with the observation of the "magic carpet" mud-like
> > material. The Gusev landing occurred within the period that the Mars
> > Odyssey readings showed the greatest water/ice deposition occurs during
> > southern Summer. Then the landing bags covering the soil may have
> > allowed deposited water/ice to be retained against
> > sublimation/evaporation. When the bags were pulled away, moist soil
> > would have been revealed.
> > That this deposition occurs may provide a means of obtaining water for
> > consumption or fuel (hydrogen through electrolysis) by future manned
> > missions. The method of a "solar still" allows water vapor in the air
> > to be collected and condensed to liquid water even in desert regions:
> > Desert Survival
> > Collect Water in a Solar Still.
> > http://www.desertusa.com/mag98/dec/stories/water.html
> > Bob Clark


==============================================================

Posted by: Bill Harris Mar 30 2006, 01:37 PM

QUOTE
I'm wondering what the latest word on the wheel is....have they found any avenues of hope...


Unofficially, my take is that the wheel is toast. An animation was posted c ouple of weeks ago that showed radial play or movement when that wheel was "rocked"; this suggests to me that there was a wheel bearing or gearbox failure. Looks terminal.

I'd guess that Spirit will find a local north-facing slope to park near for the Winter and plan to work this local area. There is still a LOT to look at here.

--Bill

Posted by: gpurcell Mar 30 2006, 02:18 PM

I think we have to accept that Spirit has become a "hopping" mission rather than a "roving" mission. Disappointing, yes...but better than a stationary or dead mission.

Posted by: ddeerrff Mar 30 2006, 03:36 PM

QUOTE (Bill Harris @ Mar 30 2006, 07:37 AM) *
Unofficially, my take is that the wheel is toast. An animation was posted c ouple of weeks ago that showed radial play or movement when that wheel was "rocked"; this suggests to me that there was a wheel bearing or gearbox failure. Looks terminal.


A bit confusing. Later information indicated the motor was showing an 'open circuit' - it was drawing no current. If it was not drawing any current, how could it have wiggled the wheel the way that it did?

Is it now a double failure; A seized garbox/bearing followed by a burned out motor?

Posted by: odave Mar 30 2006, 04:03 PM

That would be my guess - but was the slight "wiggle" we saw caused by flexing in the suspension? It wasn't clear to me, though I'm not a mechanical guy by any means...

Posted by: mars_armer Mar 30 2006, 04:12 PM

QUOTE (ddeerrff @ Mar 30 2006, 07:36 AM) *
A bit confusing. Later information indicated the motor was showing an 'open circuit' - it was drawing no current. If it was not drawing any current, how could it have wiggled the wheel the way that it did?

Is it now a double failure; A seized garbox/bearing followed by a burned out motor?

The motor is indeed open circuit. The only suggestion of a second failure has been on this board; no one at JPL has even suggested that something was amiss with the bearing or gear.

My interpretation of the motion between sols 779-780 is that it was just flexing of the wheel itself. See http://mars.jpl.nasa.gov/mer/spotlight/images/wheels01.jpg. The wheel spokes allow some "give" in the direction seen. Though I admit that I don't know the actual stiffness of the wheel spokes and I don't know what motion of the other wheels took place between the two photos.

Posted by: centsworth_II Mar 30 2006, 05:36 PM

Opportunity took advantage of the time it spent stuck with a bum shoulder to examine in detail the layers and cracks of Meridiani's sulphate pavement. Much was learned from the extended stay.

It looks like this may be Spirit's primary mode of exploration through the winter. But that's not all bad. Much can be learned by being forced to stay at an outcrop, examining it thoroughly.

Posted by: atomoid Mar 30 2006, 09:03 PM

QUOTE (RGClark @ Mar 29 2006, 07:56 PM) *
Here's one observed early in the MGS mission.

MOC--The First Year--Top 10
Water: Seepage and Ponding
Mars Global Surveyor Mars Orbiter Camera Release: MOC2-74
Mars Global Surveyor Mars Orbiter Camera Image ID: 567897575.7707
P077-07
http://www.msss.com/mars_images/moc/top102_Dec98_rel/seepage/

As I said this couldn't be proven to have been liquid. But it is interesting it was observed in connection with the Malin-Edgett gullies.
Bob Clark

Just a note (and sorry if this is getting a little OT),
How probable is it that the "ponding" sand has blown in from elsewhere and is ponding up inside the crater creating an ancient-shoreline-like outline.
It seems that if there are craters nearby to http://www.msss.com/mars_images/moc/top102_Dec98_rel/seepage/n_seep_7707sub_50perc.gif then they should exhibit similar dark ponding.
Can anyone locate any images of other craters in the vicinity to check this out?
However, if we dont have any such images, we can compare this type of sand ponding to similar other examples:

http://mars.jpl.nasa.gov/mgs/msss/camera/images/10_30_01_releases/schiaparelli/E03-00728_sub50.gif

http://www.msss.com/mars_images/moc/2004/11/13/2004.11.13.E1700009.gif

http://www.msss.com/mars_images/moc/2003/07/11/2003.07.11.R0700378.jpg

http://www.msss.com/mars_images/moc/2004/08/04/2004.08.04.R0902972.gif

I think the dark sand is probably blown in from elsewhere, collected here and forming a "pond" by virture of it staying atop the other sands, however, the source of at least some of the sand might have originated from ancient mudslides in the crater walls. However, i dont think there is enough erosion in the walls to account for this deep of a sand pond (unless its relatively onion-skin depth). so im suggesting it blew in. however, it is certainly the better example of a defined shoreline than the other examples i found.

Posted by: RGClark Apr 2 2006, 01:47 AM

Here is another image of the western end of Valles Marineris showing dense low lying fogs/clouds:



taken from this report:

Adsorption water-driven processes on Mars.
D. Möhlmann, DLR-PF, Berlin.
FIRST MARS EXPRESS SCIENCE CONFERENCE. 21-25 February 2005, ESA/ESTEC
http://sci.esa.int/science-e/www/object/doc.cfm?fobjectid=36779


Bob Clark

Posted by: Bob Shaw Apr 2 2006, 12:21 PM

Bob:

Bruce posted this link in the 'Walking on Mars without a spacesuit' thread:

http://www.agu.org/pubs/crossref/2001/2000JE001360.shtml

Bob Shaw

Posted by: ljk4-1 Apr 3 2006, 01:43 PM

MARSDAILY

- Spirit Team Gives Up On Front Wheel

http://www.spacedaily.com/reports/Spirit_Team_Gives_Up_On_Front_Wheel.html

Pasadena CA (SPX) Apr 2, 2006 - NASA mission controllers have determined that
Spirit's right-front wheel is permanently faulty, so they have decided to stop
trying to use the wheel's drive motor - and from now on the rover will run on
five wheels instead of six.

- MRO Begins Adjusting Orbit And Collecting Data

http://www.spacedaily.com/reports/MRO_Begins_Adjusting_Orbit_And_Collecting_Data.html

Posted by: Marcel Apr 3 2006, 06:10 PM

I guess we'll have to get used to decimated amounts of distances covered by Spirit. The steering, bumping, freezing and thawing finally got to her. I'm sure Oppy would have done the same if she'd have landed in Gusev. But Oppy drove with much less flexing of conductors/off-axis forces on the wheels and thus goes strong. It's amazing how long these machines hang in.

Posted by: Shaka Apr 4 2006, 09:50 PM

http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20060404a.html
Nice new press images of the "salty quagmire" Looks like we could almost 'mine' the stuff!
What would it be useful for to Mars colonists (apart from "a good dose of salts" cool.gif )?

Posted by: dvandorn Apr 6 2006, 02:50 AM

Cue MBS (Martian Broadcasting System) commercial:

"After a long day exploring the mountains, canyons and deserts of Mars, your feet ache! Those pressure suit boots just don't provide the support you need!

"But with genuine Gusev Epsom Salts, your foot aches disappear! Just add a measured cup of Gusev Epsom Salts to a gallon of hot water, and soak those dogs 'till the aches melt away!

"That's Gusev Epsom Salts! Buy some today! (Price of the gallon of hot water, roughly 3000% of your annual recreational water ration, not included.)"

-the other Doug

Posted by: abalone Apr 6 2006, 12:39 PM

QUOTE (Marcel @ Apr 4 2006, 04:10 AM) *
steering, bumping, freezing and thawing finally got to her

..........And the salt water in the bearings of course, at least that what made the wheel fall off my boat trailer.

Posted by: ljk4-1 Apr 6 2006, 08:38 PM

At a lecture for children during the early days of the MERs explorations, the biggest
question asked by the kids was "How are they getting the rovers back to Earth?"

Next was "What if an alien eats the rovers?!"

Personally I think they should stay where they end up on Mars as monuments to those
who put them there and the early days of space/Mars exploration. If space archaeologists
want to study the heck out of them, that is fine. But no obnoxious tourists trying to take
home a piece of a rover!

Posted by: RNeuhaus Apr 6 2006, 08:56 PM

The MER won't be in their places unless they will be kept in a future very big glass coliseum and their printed etiquete: Squyres has sent me to here!

Rodolfo

Posted by: Stu Apr 7 2006, 08:28 AM

I like to think that while the originals are stored and displayed in a museum on Mars, there'll be life-size (or several times life size, even better!) statues of both rovers at several points along their "trails", so future generations can go see them.

What happened to my SPIRIT poem, by the way? Did I break some Forum rule? Been away a while so apologies if I did something wrong. unsure.gif

Posted by: Marcel Apr 7 2006, 05:51 PM

Maybe it's moved to " chitchat" ? I'm interested in the poem though...

I want to talk about the wheel: the fact that they give up on it seems to indicate that they're not going to put any effort in trying to recover it. The fact that the circuit is open does not automatically (imho) mean, that it's going to be that way forever. I'd say some exercice in rotating the wheel with the steering actuator in incremental steps might restore the contact (that is, ofcourse, IF the problem is caused by a "simple" crack in a flexing conductor: a cable).

Does anyone know how the complex of steering- and driving actuators (the wrist that's in the wheel) is engineered ? Drawings will be hard....but is there any cable in there ? Or is it all done with "brushes" made of carbon ?

Ofcourse, this whole experiment's not going to make any sense if it's the driving actuator itself (the brushes) that gave up.

But maybe it's before this motor ?

How can they know for sure ?

Posted by: Jeff7 Apr 7 2006, 11:23 PM

They might have only given up on it for right now. They don't have the time to sit and mess around with it like they did with Opportunitiy's arm. Spirit needs to be on the move for better slopes. Once it's somewhere safe, then maybe they can experiment on the wheel.

Posted by: general Apr 12 2006, 10:18 AM

"Engineers are considering directing Spirit to McCool in the spring."

http://www.usatoday.com/tech/science/space/2006-04-11-spirit-home_x.htm?POE=TECISVA

smile.gif cool.gif

Posted by: RNeuhaus Apr 12 2006, 02:12 PM

QUOTE (Marcel @ Apr 7 2006, 12:51 PM) *
Ofcourse, this whole experiment's not going to make any sense if it's the driving actuator itself (the brushes) that gave up.
How can they know for sure ?

Maybe, in the winter time, there were a little more humidity and it might facility to contact the electrical points. Some strong shaking so any loose contact will stick again...So any surface kicking would solve the problem smile.gif

Rodolfo

Posted by: maycm Apr 13 2006, 04:46 PM

Just curious

Do we know how much the 'wheel dragging' contributed to the inability to climb McCool?

Would the soft ground described have been an issue regardless of the condition of the gimpy wheel?

Posted by: Marcel Apr 13 2006, 09:16 PM

I don't think so. I can't proove it, but she's been facing much harder situations w.r.t. steepness and soil properties i'd say. It's really hard to drag a blocked wheel that's loaded just as much as the other 5 (about 10 kg's of weight).....especially considering the amount of (precious) power it consumes, which is probably the main reason that they decided to return. She's in a pretty tight energy budget these days and they didn't want to face the point of no return (to far to reach McCool and to far to return to HP) due to limited amounts of watts available with the sun getting lower every day. So, i think it's not because she can not get up there due to mechanical limitations, but because of lack of energy to make it over the edge to the north face.

Posted by: centsworth_II Apr 13 2006, 09:44 PM

QUOTE (maycm @ Apr 13 2006, 11:46 AM) *
Do we know how much the 'wheel dragging' contributed to the inability to climb McCool?


I agree that Spirit would have had little trouble reaching McCool Hill with all six wheels working.

Looking at the silver lining on Spirit's limited mobility, now they will be "forced" to undertake the types of in depth and time-dependent studies that some of the scientists have been waiting to do. Like making a time lapse film of grass growing, it may not be exciting but imagine the finished product: A time lapse look at dust clearing/accumulation and maybe even ripple movement. Also super long mossbauer and APXS integrations for detailed minerology. I wonder if they'll make a really large panarama with the micro imager... like 20 by 30 frames. Big enough to make a placemat-sized high resolution image of Mars' surface. Anyone who wants can have a life size "patch of Mars" on their table or desk top.

Posted by: Jeff7 Apr 13 2006, 11:38 PM

I guess it's Spirit's turn in Purgatory, only this Purgatory is a safe place, instead of a treacherous sandtrap.
At least Spirit is in a good place to survive the winter while remaining active.

I bet they never thought they'd see Spirit last to just one winter, much less survive and then have to prepare for a second one. biggrin.gif

Posted by: edstrick Apr 14 2006, 09:35 AM

I expect that Spirit will not stay at one place during the winter, but will end up working several stations, perhaps a month or 6 weeks long on the average. I expect initial movement to get optimized instrument access to "interesting" bedrock, then parking for some long integrations and comprehensive multispectral and infrared imaging/mapping of the vicinity. Then we'll see small (meter) and larger (few meters) repositioning, possibly working along the north face of the ridge, ending each drive in the power-safe zone.

Posted by: climber Apr 14 2006, 09:58 AM

There will probably be a lot of work done to find out the best place to go versus the safer place regarding power issues (may be Shaka can help with "his" energy' map biggrin.gif ). I agree that they're not going to stay in one place. We don't want either, dont we? Does anybody heard if they've done progress about the study of the possibility to "climb" on a rock with the left from weel to get more tilt for the solar panel ?

Posted by: PhilHorzempa Apr 26 2006, 04:04 PM

I want to talk about the wheel: the fact that they give up on it seems to indicate that they're not going to put any effort in trying to recover it. The fact that the circuit is open does not automatically (imho) mean, that it's going to be that way forever. I'd say some exercice in rotating the wheel with the steering actuator in incremental steps might restore the contact (that is, ofcourse, IF the problem is caused by a "simple" crack in a flexing conductor: a cable).

Does anyone know how the complex of steering- and driving actuators (the wrist that's in the wheel) is engineered ? Drawings will be hard....but is there any cable in there ? Or is it all done with "brushes" made of carbon ?

Ofcourse, this whole experiment's not going to make any sense if it's the driving actuator itself (the brushes) that gave up.

[/quote]



I would like to pursue the issue of Spirit's wheel and its design. I am technically
literate, but do not know the details of how the MER wheel drives are engineered.

Why is it necessary to "drag" Spirit's wheel? Wouldn't it make sense to have
the option of letting it "free wheel" or would that make the design too complicated?
If the wheels on the MERs are not designed to "free wheel," what about the wheels
on the MSL Rover? It would seem logical that, sooner or later, the drives on the
Rover wheels will give out and that the option of NOT having the wheel
"lock up" would be a benefit to the mission.

Perhaps, we have been lulled into complacency by the smooth operation of the
MERs. Let us not forget that a wheel could "lock up" early in the mission of the MSL,
and the Rover would then be burdened with having to drag it for a few years.


Another Phil




QUOTE (Marcel @ Apr 7 2006, 02:51 PM) *
Maybe it's moved to " chitchat" ? I'm interested in the poem though...

I want to talk about the wheel: the fact that they give up on it seems to indicate that they're not going to put any effort in trying to recover it. The fact that the circuit is open does not automatically (imho) mean, that it's going to be that way forever. I'd say some exercice in rotating the wheel with the steering actuator in incremental steps might restore the contact (that is, ofcourse, IF the problem is caused by a "simple" crack in a flexing conductor: a cable).

Does anyone know how the complex of steering- and driving actuators (the wrist that's in the wheel) is engineered ? Drawings will be hard....but is there any cable in there ? Or is it all done with "brushes" made of carbon ?

Ofcourse, this whole experiment's not going to make any sense if it's the driving actuator itself (the brushes) that gave up.

But maybe it's before this motor ?

How can they know for sure ?


Oops - my last post omitted the credit for the quote, which I include above.

Another Phil

Posted by: helvick Apr 26 2006, 04:25 PM

QUOTE (PhilHorzempa @ Apr 26 2006, 04:04 PM) *
Why is it necessary to "drag" Spirit's wheel? Wouldn't it make sense to have
the option of letting it "free wheel" or would that make the design too complicated?
If the wheels on the MERs are not designed to "free wheel," what about the wheels
on the MSL Rover? It would seem logical that, sooner or later, the drives on the
Rover wheels will give out and that the option of NOT having the wheel
"lock up" would be a benefit to the mission.

The wheels have detents that prevent freewheeling. This is to allow the rover to drive to a location on a steep slope and remain there when the power is turned off. The amount of force required to overcome the detents is more than will be transmitted from the friction of dragging it so it remains "locked". I'd assume that the same model will apply to MSL because it is fundamentally a good one for a rover that is designed to move from point to point.

Posted by: centsworth_II Apr 26 2006, 04:42 PM

QUOTE (helvick @ Apr 26 2006, 11:25 AM) *
The wheels have detents that prevent freewheeling.


Ok, so this is a good design for normal operation. But wouldn't it be worthwhile to have an override to allow freewheeling on an irreversibly frozen wheel?

Posted by: MahFL Apr 26 2006, 04:58 PM

That would just add more weight and complexity to the design...........and I am sure the MSL wheels will be designed to last a whole Martian year. smile.gif

Posted by: Jeff7 Apr 26 2006, 06:27 PM

Yes, that's just it. The MSL is designed for long-term use.
It was assumed that the MERs would be dead after 90 sols, so they didn't really design the components to last much longer. Doing so just adds cost and potentially weight, and they were already trying to cram an enourmous amount of functionality into a small weight constraint.

Posted by: ljk4-1 Apr 26 2006, 06:32 PM

QUOTE (Jeff7 @ Apr 26 2006, 02:27 PM) *
Yes, that's just it. The MSL is designed for long-term use.
It was assumed that the MERs would be dead after 90 sols, so they didn't really design the components to last much longer. Doing so just adds cost and potentially weight, and they were already trying to cram an enourmous amount of functionality into a small weight constraint.


Here's a question: Why didn't they design the MERs to last longer?

They knew the rovers couldn't move fast or far, and there was no
guarantee that they were going to land in interesting places they could
reach in time (Gusev almost turned out that way).

So why didn't they plan to make them last at least half a year, if not
more, to ensure success? $400 million a piece is a lot to spend on hope
and luck.

Posted by: djellison Apr 26 2006, 06:35 PM

Dust. They expected the dust to kill them soon after 90 sols.

To engineer the robustness and longevity to last 1000 sols ( i.e. design spec of 3000 sols as they design for minimum component life of 3x the requirement as I understand it ) from the outset, it would have put mass, volume, time and money over the edge.

Doug

Posted by: mwolff Apr 26 2006, 06:46 PM

[quote name= quote in reply -removed
[/quote]

Dust was only one factor. A lot more energy was expected to be expended in keeping things warm
at night and that would "wear down" the batteries' storage capacity...so eventually, the inability to spend the power to keep warm at night allows thermal cycling to kill some critical component. It turns out that the rovers had much better thermal performance than assumed (such that even the massive amount of "Deep Sleep" by Opportunity doesn't seem to have broken anything...though one might have things to say about the miniTES performance, at least for atmospheric observations rolleyes.gif ) ...and of course, the "dust cleaning events" helped avoid the dust problem mentioned by Doug which would certainly have been expected in an extended mission.

Posted by: Bob Shaw Apr 26 2006, 08:39 PM

FWIW, the Lunokhod wheels were, like the MER wheels, each equipped with an electric motor, but provision was made to 'blow' the motor if it stalled so that the wheel could freely turn. I don't think this feature was ever actually used.

Bob Shaw

Posted by: djellison Apr 26 2006, 09:14 PM

Blimey - I'm reaching WAYYy back into the distant past here - I seem to remember that they were a few degrees above predicts whilst still sat on the lander, but I've not heard anything since then.

Trying to convert that heat into a 'power saving' obviously requires more MER facts than we mortals have.....

Call it 4 degrees. Say we have an equiv within the structure and contents of the WEB of say 20kg of water in terms of equiv thermal capacity.

Specific heat is 4186J, x 20, x4 - 334880 Joules of energy.

3600 seconds in one hour, 1 Whr thus provides 3600 Joules - so 4 degrees of heat in 20kg of water is 93 Whrs. I have no idea if that relates in any way shape or form to the potential for saved power onboard a rover, but it's a thought isn't it.

Still waiting for that sky hemisphere eh Mike ph34r.gif

Doug

Posted by: helvick Apr 26 2006, 09:50 PM

QUOTE (djellison @ Apr 26 2006, 09:14 PM) *
3600 seconds in one hour, 1 Whr thus provides 3600 Joules - so 4 degrees of heat in 20kg of water is 93 Whrs. I have no idea if that relates in any way shape or form to the potential for saved power onboard a rover, but it's a thought isn't it.

It is a thought alright. The original engineering requirements documents go into quite a bit of detail on the thermal performance and the amount of IR heat energy the Rovers would be subjected to on the surface. Looking at the charts it seems that the design specified downward IR flux that varied from 20-50 watt/m^2 throughout the day when Tau was low up to 20-75watt/m^2 when Tau was around 2. That amounts to between 600 and about 1000 whr/sol for the rovers since the downward IR seems to remain around about ~20watt\m^2 even at night.

All of this is very speculative though considering that we have no idea how well insulated the rover body is and even if we had such detailed thermal model data we still don't really know what the temperature limits actually are. It could be that the components can just handle much colder temperatures than they had been designed for or it could be that they are managing to remain warmer than expected. I suspect the former because the latter would surely have led to real overheating problems.

Posted by: djellison Apr 26 2006, 09:59 PM

QUOTE (helvick @ Apr 26 2006, 09:50 PM) *
real overheating problems.


LIke the one's that resulted in cancelled UHF sessions whilst still on the lander, and turning the spacecraft off in the afternoons whilst atop Husband Hill smile.gif

Doug

Posted by: helvick Apr 26 2006, 10:15 PM

QUOTE (djellison @ Apr 26 2006, 09:59 PM) *
LIke the one's that resulted in cancelled UHF sessions whilst still on the lander, and turning the spacecraft off in the afternoons whilst atop Husband Hill smile.gif

I was thinking that as I was typing but at that time the total insolation was almost 20% higher than the maximum that would ever have been planned for in the original mission and even with the most optimistic hope for extended operations so overheating at that point wasn't really surprising. I seem to recall though that overheating was mentioned much earlier in the mission too but I can't remember when so maybe the insulation is just working much better than intended.
My comment was based on my own opinion that it would be much more of a surprise that the insulation on the rover worked better than expected than having components survive more repeated heating\cooling cycles than they had been designed for.
Hopefully there will be some nice papers on this at some stage. smile.gif

Posted by: mwolff Apr 27 2006, 02:45 AM

QUOTE (djellison @ Apr 26 2006, 04:14 PM) *
[snip]

Still waiting for that sky hemisphere eh Mike ph34r.gif

Doug


...in LOCO! biggrin.gif

--mike

QUOTE (helvick @ Apr 26 2006, 05:15 PM) *
My comment was based on my own opinion that it would be much more of a surprise that the insulation on the rover worked better than expected than having components survive more repeated heating\cooling cycles than they had been designed for.
Hopefully there will be some nice papers on this at some stage. smile.gif


rover naps were definitely inserted into the tactical planning process as a result of the need to "cool". you'll get
more reliable information from Emily, though. Atmospheric STG concerns about thermal issues was typtically limited to the amount of power that had to be used to pre-heat before overnight miniTES observations...

QUOTE (mwolff @ Apr 26 2006, 09:44 PM) *
...in LOCO! biggrin.gif
--mike
rover naps were definitely inserted into the tactical planning process as a result of the need to "cool". you'll get
more reliable information from Emily, though. Atmospheric STG concerns about thermal issues was typtically limited to the amount of power that had to be used to pre-heat before overnight miniTES observations...


...though apparently grammar wasn't a concern either. blink.gif

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