The Storm, Dust storm of 2007 Options

[OWW]

Oh no...This is getting bad:

The new and potentially bleak outlook is a stark shift from the prognosis earlier this week.

The dusty squall has reduced direct sunlight to Mars' surface by nearly 99 percent, an unprecedented threat for the solar-powered robotic explorers. If the storm keeps up and thickens with even more dust, officials fear the rovers' batteries may empty and silence the robotic explorers forever.

Opportunity's energy-gathering ability has been slashed to a dangerous 280 watt-hours-enough power to light only three 90-watt light bulbs.

"The worst-case scenario is that enough dust in the sky decreases solar energy to the point that we have to shut down too many things to save power," Lemmon said. "The rovers keep their battery alive by keeping their electronics alive."

"The reality of the situation is that we're limited as to what we can do from the ground by cutting power use," Callas said. "If it continues to worsen and stay that way, it's a survivability issue for Opportunity. If Mars wants to kill the rovers, it can."

http://www.space.com/news/070705_dusty_rovers.html

[kungpostyle]

This is starting to look like it might need it's own topic.

http://www.space.com/news/070705_dusty_rovers.html

With Home plate and the inside of Victoria on the menu I really hope this blows over.

[helvick]

99% drop in direct beam flux is Tau of around 5.2. That's slightly worse than the highest Tau levels measured by the Vikings in 1977.

Edited. Doh! My bad - it's actually about 4.6 which is not quite as bad as the worst the Viking's saw in 1977.

[Guest_Bobby_*]

I saw this article on Yahoo News and thought everyone might want to see it regarding both Rovers on Mars.

Martian dust storm affecting twin rovers:

http://news.yahoo.com/s/ap/20070705/ap_on_...bvYqwxIae_737YB

[Stu]

Hope this doesn't get any worse... don't want to see pics like this coming down...

[mchan]

It would be awesome if the pictures can show something visually dramatic like that. Unfortunately, the pictures appear to show the the landscape getting slowly murkier and murkier. An animated movie would be awesome.

It's probably not too bad if any pictures can still come down. It's bad if no pictures can come down.

[Stu]

I know there's no way we'd ever get pics like that, I was just imaginin' ...

[Oren Iishi]

Can the rover be shut down until the storm passes? Or at least put in sleep mode?

[MarsIsImportant]

Yes, but the heaters need to be on to keep the electronics in safe condition. Nomatter what, Opportunity needs a certain level of power to survive. The latest news suggests that those power levels are uncomfortably close to that lower limit even with sleep mode.

This is a very unfortunate turn of events. But if opportunity survives intact, then this storm and its aftermath is an incredible new science opportunity for the rover. Let's just hope that the dust storm does Not get any worse than it has over the 4th of July.

If you believe in the Gia hypothesis, then maybe Mars was just celebrating with it own brand of fireworks! ;-) ...the kind that some western states had to ban because of the drought.

[Tom Tamlyn]

What is the impact of the storm on dust deposition rates? Is the activity mostly too high in the atmosphere to blow heaps of dust onto the solar arrays?

TTT

[djellison]

Strangely, if I get this right - regional dust storms are quite good because they cause high wind speeds ( note the cleaning that Opportunity got just over a week ago ) - BUT I would imagine that there comes a point when the dust loading, whatever the wind speed, must cause increased deposition.

Doug

[ngunn]

It must all fall down when the wind stops. If it causes almost complete obscuration when it's airborne then I fear it will do the same when it settles, unfortunately.

[djellison]

What happened after the, admitedly much more modest regional storm, that Opportunity had in the 600-ish range - the one that made it sleep in late one morning?

Doug

[Guest_Sunspot_*]

Are there any pictures of the dust storm anywhere? This isn't looking good.

[Pavel]

Would not the air be warmer if the airborne dust is consuming the solar light? It's summer in the southern hemisphere, and Mars should be close to its perihelion, so maybe the power requirements for the heater are not so high as in the middle on the winter?

[djellison]

That's true - I remember the depths of Spirits winter, and they mentioned that they got away with less than the 240whrs they thought they needed, because the vehicle ended up staying warmer than they expected.

Doug

[ustrax]

it is my oppinion that if Oppy survives this we should take to Ithaca...in shoulders!

[slinted]

Are there any pictures of the dust storm anywhere? This isn't looking good.

I'm sure there are other resources for finding amateur images of Mars, but the Mars Observers Yahoo group isn't a bad place to keep track of daily images of the storm. Imaging Mars isn't too easy now , but I'm consistently impressed with what you can see even in low res images. Unfortunately, you need to join the group to read the messages/see the images.

[Tom Tamlyn]

Is the MRO's Mars Climate Sounder able to return observations that are helpful in understanding the current dust storms? Are the observations useful for rover operations or only for long-term assessments of the atmosphere?

TTT

[helvick]

What happened after the, admitedly much more modest regional storm, that Opportunity had in the 600-ish range - the one that made it sleep in late one morning?
Doug

The purple line is a 30 Sol moving average and the red line is a 50 sol moving average trend line on that. I had to do that in order to dampen out the noise sufficiently to see any trends at all but it means that the data in those lines is shifted to the right by 30 and 80 sols so keep that in mind.
It is pretty clear (to me maybe others differ) that stormier high Tau weather (such as seen around sol 370, 420 and 510) are followed rapidly by an increase in dust deposition rate from ~0.2% per sol to ~0.3% per sol. I would assume that the much more severe dust levels we are now seeing would result in higher deposition rates fairly soon but we'll only know for sure once it happens.


Also Pavel's comment on night time temperatures is correct - at Tau=2 night time minimum temperatures would be about 15-20 degrees warmer IIRC and I'd expect that Tau-4 would improve that again. The effect is the similar to that seen here on earth where cloud cover raises night time temperatures.

That said the stuck heater on Oppy means she draws a bit more juice than Spirit. Again IIRC the heater in question draws 15watts and is activated if the atmospheric temperature falls below -52C and stays on until it warms up past -42c - they use Deep Sleep to keep it off during the night however I think they still have to live with it being stuck on for at least two hours per Sol under the best conditions so Oppy needs about 30 Whr per Sol more than Spirit.

[john_s]

Here's another nice site for amateur images of Mars, and other Mars news:

International Mars Watch

John.

[slinted]

Dr. Lemmon has an update on his dust devil page, with some specific tau figures:

New, sol 1244: The recent dust storm activity has been intense for both rovers. Opportunity experience optical depths of (starting sol 1215) 1.3, 1.5, 1.7, 2.2, 2.6, 3.0, 3.3, 2.7, 3.1, 4.0, 4.1, rising from a background of 1.0. Spirit's opacity remained near 0.9 until starting on 1239 it went to 1.0, 1.0, 1.2, 1.3, 1.6, 2.4, 2.3. On sols 1239 and 1244, movies caught some dust devil activity. Sol 1240's movie did not see any activity. Recent sols have seen minor dust cleaning and deposition, but I'm not aware of major changes. The sol 1244 movie shows a much more indistinct horizon. The winds at Meridiani, especially, have probably been quite intense at times.

[Pando]

Dr. Lemmon has an update on his dust devil page, with some specific tau figures:

Tau is 4.1 now!!!

[fredk]

Tau is 4.1 now!!!

That's a bit better than our estimate of 4.6 based on the 99% direct sunlight attenuation quoted in the Space.com story. From Lemmon's site it was 3.1 on sol 1223. Was that a sol 1224 figure, Pando?

[Astro0]

Just got some feedback that Sol 1225 Tau is 4.125.
Oppy is at 255Whr.

Pray!

[Stu]

Murky sky... hang on in there, Oppy...

[Guest_Bobby_*]

The dust storm has delayed Oppy from entering Victoria Crater for now:

http://www.jpl.nasa.gov/news/features.cfm?feature=1411

[djellison]

What with the stuck shoulder joint heater, 255 is a lot worse for Opportunity than for Spirit

Doug

[Tesheiner]

Just got some feedback that Sol 1225 Tau is 4.125.
Oppy is at 255Whr.

Pray!

Checked the imaging plan for sol 1226 and it's only composed of two or three tau measurements. It remember Spirit during mid-winter times and looks like the available power would be not enough to run other things.

Keep strong little rover!

[belleraphon1]

Dust storm.... high tau...... high winds.....

Knowledge always comes with a price......

Yes, hang in there little rovers......

Craig

[sattrackpro]

There is an interesting article about dust storms on the hubble-site HERE - that foretells a possible second following storm. (Hope not!)

Here's the relevant excerpt:

After three months, the storm is beginning to wane. The planet's shrouded surface has cooled, and this allowed the winds to die down and the fine dust to begin settling. However, Mars is approaching the closest point of its orbit to the Sun. Once the atmosphere begins to clear, the return of unfiltered solar radiation may trigger additional high winds and kick up the dust all over again. This one-two punch has been seen in previous Mars storms for centuries.

The article is old - but could multiple storms be caused, or have been caused in this fashion with this episode?

[helvick]

Multiple major storms do happen in some years - the Vikings saw two in 1977 for example.

[mhoward]

At least she was still taking pictures on sol 1225, and the calibration target looks clean. It's now morning on sol 1226. Let's keep our fingers crossed...

[tedstryk]

Speaking of Hubble, it will look at Mars near the end of this month to help with MARCI's calibration woes, but in the process, it may catch the aftermath of this.

[Guest_Analyst_*]

... and the calibration target looks clean.

Very clean I have to say. Probably better than before?

Analyst

[centsworth_II]

Very clean...

But almost no shadow. There's the rub.

[hortonheardawho]

colorized Spirit sol 1244 ( July 4, 2007 ) L0 1x2:



Just a guess.

[diane]

Just got some feedback that Sol 1225 Tau is 4.125.
Oppy is at 255Whr.

Does anyone know what Oppy's power reserves were before the storm got bad? I assume she can withstand some days of low power input, if the batteries were well-charged before the Tau got so high.

She doesn't have to survive a whole martian winter on low power.... Hopefully just a few days.

[dvandorn]

I'm actually a little more worried about Spirit than I am about Oppy. This dust is all still entrained in the atmosphere, it hasn't really started to fall out yet. I don't know why, but I have this gut feeling that Meridiani may collect less dust from this storm than Gusev eventually will. Maybe because there is less overall dust accumulation on the ground at Meridiani than there is at Gusev; it just feels like Meridiani doesn't collect dust as effectively as Gusev does. (Maybe Gusev's crater rim causes a large-scale swirl in the winds that tends to make dust collect within, while the lack of any such circulation patterns at Meridiani keeps it from getting dumped on nearly as much.)

I guess I'm thinking that the dust ought to have specific patterns of fallout, based on when in the year the storms occur and what the wind patterns are like at the time. It also may have something to do with your distance from where the storms start and how they grow. It just feels like, since Oppy was closer to this storm as it formed, it may actually get away with having less of the dust dumped on it than other places on the planet -- perhaps even halfway across the globe.

Also, rather obviously, the polar caps display a process in which dust is often sandwiched between layers of dry ice. It may well be that a majority of the dust pulled up during these major storms ends up being deposited at the fall/winter pole, to which the air is flowing and where the air is precipitating out and plating itself onto the ground. That would tend to make sense from a global circulation pattern perspective.

-the other Doug

[akuo]

Some new information in this National Geographic article.

Jacob Matijevic is confident of rover survival.

[kungpostyle]

Jake seems confident;

best rover news I've heard in a couple of days!

[mhoward]

A handful of sol 1226 images are online. Just solar-filter images so far.

[MarsIsImportant]

Sol 1226...look how clean the rover looks!

http://qt.exploratorium.edu/mars/opportuni...R9P1962R0M1.JPG

[CosmicRocker]

She looked very clean, but that image should be from sol 1223. I suspect she is still pretty clean, despite the dust storm.

It's nice to hear that somewhat positive news from national geographic. I can't help but wonder if this would have been more of a survivability issue for the rovers if they hadn't been cleaned by the earlier winds. I also can't help but wonder if such early, cleaning winds might be expected prior to a dust storm.

[Guest_Sunspot_*]

www.spaceweather.com reports the storm has intensified and grown.

MARS UPDATE: A late-June dust storm that delayed Mars rover Opportunity's descent into Victoria Crater has intensified and spread around the planet, reports veteran observer Jim Melka of St. Louis, Missouri. On July 6th, the view through Melkin's 12-inch telescope showed "a chain of five dust clouds over Mare Cimmerium," he says. "One cloud is very close to the location of the Opportunity's twin, Spirit." Stay tuned for updates.

[djellison]

Strong winds with the storm mean that Opportunity's going to be VERY clean as long as we don't catch a big chunk of dust when...er...the dust settles, as it were

Doug

[vikingmars]

As a reminder, here are the fully calibrated comparison pics showing the minimum of light level encountered by Viking Lander 1 on sol 324 (1977).
Tau was between 5 and 6 depending your reading sources...
Enjoy ! (if I may say...)

Attached thumbnail(s)

 

[Stu]

Hey, welcome back vikingmars! Missed your gorgeous pics!

Just for my own interest, not claiming 1000% accuracy or anything, but there's a LOT less detail visible on them that hills...

( left: June 13th, right: yestersol. )

[deglr6328]

how do we know how high the winds are at the surface?

[djellison]

Well - from the rovers we don't really. For dust to be leaving the rover it has to be 'higher' than normal. Orbital imagery can track dust, clouds etc and gauge wind speeds that way.

Just a bit of fun from the values on Mark's page. Looks like we might be seing the turn in the trend- but as you can see, Meridiani already fooled us once in that regard.

Doug

Attached thumbnail(s)

 

[belleraphon1]

Sol 1226...look how clean the rover looks!

http://qt.exploratorium.edu/mars/opportuni...R9P1962R0M1.JPG

Yes.... but what goes up must come down. All that dust in the upper atmosphere has to settle out at some point..... and those beautiful solar panels make a nice target....... just hope there is a balance between dust deposition and wind cleaning events....

Worried....... stay warm little rovers.... hold on.............. if I could I would gently blow your petals clean...

Craig

[belleraphon1]

OK - doing a total inline quote is one thing - doing it with your own post is madness!
Pointless quote removed! - Doug


And shine a light on your petals!!!!!!!

Craig

[CosmicRocker]

Yes, whatever goes up must come down, but thanks to the winds it also travels sideways. I guess it's kind of a crap shoot. As the forces blowing dust around this planet run out of energy, let us hope that most of the entrained dust falls somewhere else. Everyone, cross your fingers.

[djellison]

another sols info on Marks page.

Attached thumbnail(s)

 

[clt510]

another sols info on Marks page.

Thanks for posting this, but could you provide the URL link for these?

THX.

Carrick

[centsworth_II]

... could you provide the URL link for these?

http://www.lpl.arizona.edu/~lemmon/mer_dd.html
(The values are in the text at the top of the page.)

[Tesheiner]

Let´s hope for this descending trend in the tau values.
Meanwhile, Opportunity´s imaging operations are limited to tau measurements only since sol 1226. Same is expected/planned for tosol (1229) and tomorrow.

[CosmicRocker]

The early trend is in the hoped-for direction, but Dr. Lemmon's page still has no new tau values as I go to sleep tonight.

New, sol 1249: The recent dust storm activity has been intense for both rovers. Opportunity experience optical depths of (starting sol 1215) 1.3, 1.5, 1.7, 2.2, 2.6, 3.0, 3.3, 2.7, 3.1, 4.0, 4.1, 3.7, 3.0 (to sol 1227-sol 1228 data aren't due until 1229 PM due to energy conservation measures from weekend plan), rising from a background of 1.0. Spirit's opacity remained near 0.9 until starting on 1239 it went to 1.0, 1.0, 1.2, 1.3, 1.6, 2.4, 2.3, 2.1, 2.1, 2.4, 2.3 (to sol 1249). New, sol 1244: On sols 1239 and 1244, movies caught some dust devil activity. Sol 1240's movie did not see any activity. Recent sols have seen minor dust cleaning and deposition, but I'm not aware of major changes. The sol 1244 movie shows a much more indistinct horizon. The winds at Meridiani, especially, have probably been quite intense at times.

We don't have any imagery from sol 1229.

CODE

5. What EDRs are missing?

Missing EDRs by sequence number and image type:  (This compares the SSF requests
to actual EDR PDS image files.  The missing ones may not have made it off the rover
yet, may not have been processed by MIPL yet, or may not have been taken as requested.)

Sol   Seq.Ver  ETH ESF EDN EFF ERP Tot  Description
----- -------- --- --- --- --- --- ---- -----------
01229 p2685.15 2   2   0   0   2   6    pancam_tau
01229 p2687.15 4   4   0   0   4   12   pancam_wide_range_tau
01229 Total    6   6   0   0   6   18

It does not appear that sol 1230 will be very active.

CODE

4. What EDRs did we request?

Expected EDRs by sequence number and image type:

Sol   Seq.Ver  ETH ESF EDN EFF ERP Tot  Description
----- -------- --- --- --- --- --- ---- -----------
01230 p0099.01 2   0   0   2   0   4    navcam_stereo_1_bpp_no_actuation
01230 p1550.01 2   0   1   0   0   3    navcam_tau
01230 p1550.01 0   0   0   0   0   0    navcam_sun_pri_57
01230 p2685.15 2   2   0   0   2   6    pancam_tau
01230 p2687.15 4   4   0   0   4   12   pancam_wide_range_tau
01230 Total    10  6   1   2   6   25

Sol 1231 is not a high energy consumption day, either.

CODE

4. What EDRs did we request?

Expected EDRs by sequence number and image type:

Sol   Seq.Ver  ETH ESF EDN EFF ERP Tot  Description
----- -------- --- --- --- --- --- ---- -----------
01231 p1550.01 2   0   1   0   0   3    navcam_tau
01231 p1963.06 2   0   0   2   0   4    navcam_tracks_loco_pri57
01231 Total    4   0   1   2   0   7

I am still optimistic that it is getting better for our rovers.

[Pando]

The early trend is in the hoped-for direction, but Dr. Lemmon's page still has no new tau values as I go to sleep tonight.

I am still optimistic that it is getting better for our rovers.

2.9. So am I

[djellison]

Ignore the last Opportunity point - that's my guess, not an actual value.

I THINK...(well, guess) that we're closer to the 400 whr level rather than the 255 whr level now.

Doug

Attached thumbnail(s)

 

[jaredGalen]

Out of curiosity, to reach Tau levels as we saw here (e.g. 4.0) would it typically take a storm to throw it up?

As such, would there be globally increased wind levels? Or can the storm be localised and kick the dust up into the higher atmosphere, leaving regions further from the storm with normal winds (virtually none) but high Tau? I don't know how low atmospheric pressure affects all that.

While high Tau is bad for solar junkies like Oppy and Spirit, will these events have helped glean a better understanding of mass air movement on Mars? What will they be trying to learn from the past few weeks?

Sorry for all the questions, guess I'm just thinking out loud....

[Tom Tamlyn]

During Monday's Phoenix Mission press conference, Doug McCuistion, NASA's Mars Exploration Program manager, gave a brief but upbeat report on Opportunity's ability to survive the storm. I thought I also heard him say that Opportunity could function at a power level of about 100 watts. (It appeared later on that at least one reporter interpreted the 100 watts comment as referring to Phoenix, but I recall it as relating to the rovers).

That's a lot lower than the approximately 270-80 watt figure that's been discussed here as the rover's survival threshold. I assume that a good deal of the difference is represented by the fact that less power (no power?) is needed for keeping the electronics warm during the summer season.

Aside from heating, does anyone know what functions require power (and how much) for minimum survival? Does the rover draw no power at all during Deep Sleep?

TTT

Edit to fix typo.

[centsworth_II]

I thought I also heard him say that Opportunity could function at a power level of about 100 watts.

He did say that. But it's more like "stay alive" than "function".
I think the only thing Opportunity would be doing at that power
level would be recharging. I don't know about heating. Has
deep sleep been used during the day? I envision it as a
deep sleep/recharge situation.

[Pando]

To cut down power consumption, they would also need to reduce communication windows.

[Tom Tamlyn]

Emily has posted a comprehensive discussion on her blog, with a full transcript of McCuistion's comments.

Most intriguing was this, which I had forgotten: "We have the ability to charge the batteries below 100 Watts. We can do imaging even below 100 Watts. So we can select the instruments we want; we don't communicate with the orbiters as frequently."

Emily has also promised to try to obtain more information.

TTT

[jaywee]

Emily has also promised to try to obtain more information.

Emily, could you also ask (or anyone else) how the storm affects the surface day/night temperatures ?

jv

[MarsIsImportant]

I've been looking for images of the magnets on the rover. I found a few; but I wish I could find a whole lot more.

These are the most recent images downloaded in order.

June 27th, 2007

http://qt.exploratorium.edu/mars/opportuni...R9P2976M2M1.JPG

July 1st, 2007

http://qt.exploratorium.edu/mars/opportuni...R9P2976M2M1.JPG

July 3rd, 2007

http://qt.exploratorium.edu/mars/opportuni...R9P2936M2M1.JPG

July 9th, 2007

http://qt.exploratorium.edu/mars/opportuni...R9P2936M2M1.JPG

As you can see, the wind is blowing some of the magnetic particles off of the magnets. I think that is an indicator of just how strong some of these winds must be.

[OWW]

The first two are both from Sol 1217 and the last two are the same picture, from sol 1223.
So there is no evidence for more than one gust.

[djellison]

Yup - raw images 101. The date something appears at the Exploratorium has little relation to when it was actually taken. The file name shows you when it was taken

1M236222506EFF85R9P2976M2M1

That's the time tag in red.



Doug

[Tom Tamlyn]

jaywee,

Helvick, the forum expert on Martian solar power, briefly discussed the effect of dust on surface temperature earlier in this thread (post #20, responding to post # 15).

Of course it would also be great to hear what the Mars weather scientists are learning and expect to learn about this storm from the instruments in orbit.

TTT

[MarsIsImportant]

The first two are both from Sol 1217 and the last two are the same picture, from sol 1223.
So there is no evidence for more than one gust.

I wasn't suggesting evidence for any more that one major gust. Actually we don't know whether it was just one gust...just one time interval when the change occurred. My point was that it was strong enough to clean the magnets significantly.

BTW the red tag continues to confuse me. They just look like a lot of number to me.

[djellison]

http://midnightmarsbrowser.blogspot.com/

Get it.

Be confused no more.



Doug

[CosmicRocker]

I just noticed this Aviation Week Article dated July 8th (Rover Ready for Dangerous Descent After Dust Storm) It seems to have a little new information about the dust storm and operations planned for inside the crater.

"For several sols [Martian days] we saw the opacity ["tau levels"] increasing at a rate of about 0.3/sol on Opportunity. It peaked at about 3.3, which is by far the highest value we have seen to date for either rover," says Squyres. But late last week, it was back down to 2.66--which is a large and sudden drop, indicating dust levels are highly variable.

[elakdawalla]

Hi guys, I went to the Mars meeting at Caltech today and planned to get some answers but had to leave because I wasn't feeling well. I did catch Ray Arvidson before I left and asked him about the 100-Watt number and he said that was an error. A woman with him said she thought the number was more like 280 or 290.

--Emily

[Ant103]

Hi all

A few times without posting because I've broken my wifi pcmcia card (thanks to gravity who have made fallen my laptop ). The problem is now solve.

I learned that a dust storm hit our rovers.... And Olivier made us a little visit

So, a picture I've made showing the inversion phenomena through the sky during a dust storm :


And here, a color panorama of Victoria crater during the storm :


In expecting that the storm will not during a lot of time

It's a pleasure to read you at new

[Tman]

BTW the red tag continues to confuse me. They just look like a lot of number to me.

This site on the MER homepage explains the whole image code.

[helvick]

That 255 whr figure for Sol 1225 is bugging me (Sorry Astr0 - feel free to object right back )

I calculate that at a Tau of 4.1 on Sol 1225 for Opportunity she should have generated around 310Whr.

All of the other numbers that I've seen recently indicate that the insolation model I'm using underestimates the real values by 10% or so ( e.g. on sol 1221 @ Tau=3.3 the MER team have published a value of 402 Whr when I estimated about 360 Whr ). That would make me expect a real value of about 340 Whr if the Tau value of 4.1 is correct. Furthermore I really suspect that there was at least one small (5% or so) cleaning event sometime between Sol 1211 and 1220 which would put the number closer to 355Whr.

The most likely reason for this is that the diffuse Insolation model I'm using becomes increasingly unreliable as Tau rises past ~3 but it is also possible that the 255 Whr number isn't accurate. I'm also very surprised at Opportunity being able to function at all at that level, my understanding all along has been that 270-280Whr is extremely marginal for her given her stuck heater.

Very much looking forward to published numbers from the team.

[Floyd]

BTW the red tag continues to confuse me. They just look like a lot of number to me.

The code is explained here.

Edit: sorry didn't see Tman's post as was reading the previous page.

[fredk]

That 255 whr figure for Sol 1225 is bugging me

Well, we had that report that began this thread that the direct sun was attenuated by "nearly 99%" (tau = 4.6), with power at 280 Whr. The report was dated the 5th (sol 1225), though the sol is not mentioned in the article. Does that fit your model better?

The more recent data show a peak at 4.1, so 4.6 seems to have been an error. I suppose at times like this with everyone wanting tau values, numbers get out that aren't very accurate. Let's hope the clearing trend continues!

[hendric]

Is it possible that the Tau reading is just a single point on a line, ie the Tau could be 4.6 now, but could be lower or higher before and after that reading. Tau comes from looking at the sun, right? So power produced could be slightly off from what you expect because the dust isn't consistent either across the sky, or from morning to evening.

[edstrick]

high dust opacity drops daytime temperatures, but raises nighttime temperatures.

Local dust storms, if strong, show strongly convecting or at least dynamically churning clouds, often with some mixed-in condensation clouds, as seen from orbit. They can probably be quite opaque, but then the dust spreads out and disperses, like the storm that happened shortly before Beagle and MER's arrived.

Globe-encercling storms have been observed from orbit in development phase 3 times (2 viking orbiter storms and the 2001 storm), and once in the decay phase (the greatest of all, the 1971 global storm: Mariner 9.) Storm heating probably has a massive "ripple" effect on the adjacent atmosphere, as well as strongly boosting global atmospheric thermally-driven tidal oscillations, and can probably cause unusually strong winds even in non-storm-dust affected areas before the dust arrives. Areas near an active storm may plausibly have such strong induced winds that there is strong local dust scouring and lifting, causing a propagation of the main storm, starting solar heating of the newly raised dust in a sort of chain-reaction effect.

We just don't really understand the meteorology of storms and their growth. Vikings got some good photography at intervals, as well as infrared thermal mapper data. The 2001 storm was before Odyssey's arrival, I think but had good coverage by MGS's wide angle cameras and the thermal infrared spectrometer. With the wide angle cam on recon orbiter and the climate sounder, we're getting our first meteorology instrument look at a big storm :-) I hope to hell the've switched the instrument back into scanning mode for the storm.

[Pertinax]

Is it possible that the Tau reading is just a single point on a line, ie the Tau could be 4.6 now, but could be lower or higher before and after that reading. Tau comes from looking at the sun, right? So power produced could be slightly off from what you expect because the dust isn't consistent either across the sky, or from morning to evening.

I would be strongly suspicious of any answer other than 'absolutely'.

The dust in the atmosphere certainly varies on short time scales -- they do on earth. Also, as you noted the extinction of sunlight would be greater for lower sun angles than higher for any given tau, as the effective optical depth increases with a lower sun (sun having to shine though a greater volume of air & dust). I have wondered myself how for a constant tau the sky appearance (including of course scattered light) would vary.

FWIW: http://marswatch.astro.cornell.edu/Bell_etal_SkyColor_06.pdf

-- Pertinax

[helvick]

Thanks for the input folks.
The MER team's Tau values into account the solar zenith angle and the resulting increase in air mass as do my calculations for beam insolation. You can see this in the published Tau charts - the air mass numbers and DN's vary as they should with the changes in the local true solar time of the Pancam shots the readings are based on and the resulting Tau values are pretty consistent throughout each sol (on the occassions that multiple readings are taken)

However even though they are consistent there is definitely a daily cycle - Tau (generally) increases slightly over the course of a normal sol and then clears up slightly again overnight. Whether this cycle is more or less pronounced during a storm I can't say but for the vast majority of the year the variation is <0.1 over the course of each sol. To explain the variation I'm puzzled by we would need a variation of about 2.0 for about half the sol.

It is probable that part of the explanation is that very short time scale events (passing higher density dust flurries for example) are causing significant variations in Tau during the day.

[Pertinax]

For fun, a question that I can probably dig for an answer for if there is not a quick one available here.....

Question: Is there engineering data available from the rovers (in the PDS I would presume) which reports the output from the solar arrays? If so, what is the temporal resolution (and averaging period if any) of the data?

It would be fascinating data if available in decent resolution.


-- Pertinax

[climber]

I was wondering if we have, here on Earth, the equivalent of Marsian's dust storms?
For exemple, dusts coming from deserts that goes very high in our atmosphere where the pressure could be comparable to what it is on Mars?

[helvick]

Pertinax wrote: It would be fascinating data if available in decent resolution.

I've been saying that for years.

I don't think we'll see it any time soon unfortunately. It's engineering data that doesn't directly feed into any science data (as far as I know) and since some of the engineering data skirts into ITAR terrain releasing any of it requires that lawyers clear it first. That's just asking too much for data that is only of marginal interest at this stage in the mission. It would be great if someone used the data as part of a paper (say on short time scale variations in atmospheric opacity) and got it published that way,

The temporal resolution was good enough for the team to be able to specify that Spirit's last major cleaning event happened at 13:20 local time (IIRC) so I think it's at least possible to get it down to 10 minute intervals.

[tty]

I was wondering if we have, here on Earth, the equivalent of Marsian's dust storms?
For exemple, dusts coming from deserts that goes very high in our atmosphere where the pressure could be comparable to what it is on Mars?

Desert dust certainly can spread quite far. For example a fair amount of the soil on Bermuda is very fine saharan dust accumulated over hundreds of thousands of years. However terran "weather" in almost all forms very largely happens in the troposphere. For example despite the vast amount of salt spray created continuously over the oceans essentially nothing gets into the stratosphere (otherwise the sky at twilight would be yellow from the Na and the ozone layer would be destroyed by the Cl).

About the only exceptions is material from volcanic eruptions and large impacts which gets injected into the stratosphere with consequent climate effects extending over years (dust in the troposhere is washed out by rain fairly quickly).

[djellison]

Saharan dust landing on cars in the UK isn't uncommon - I remeber two distinct occurances of that in the past decade or so.
Meanwhile - updated to 1230/1250 actual figures

Massive kudos to Mark for putting these on line so quickly.

Attached thumbnail(s)

 

[Guest_Oersted_*]

The Sirocco:

Some nice pics here of the dust blowing from the Sahara up towards Europe.

http://en.wikipedia.org/wiki/Sirocco

[djellison]

Infact -thinking about it - I remember finding comedy in the fact that a Sirocco was dumping sand on my mums VW Sirocco.

Doug

[climber]

Infact -thinking about it - I remember finding comedy in the fact that a Sirocco was dumping sand on my mums VW Sirocco.
Doug

Did any DD cleaned it up?

[J.J.]

A similar phenomenon we have here is "muddy rain"; it isn't really muddy, of course, but it is rich enough in dust that was lofted into the atmosphere in arid West Texas and deposited here to leave a significant film on one's car.

[Astro0]

'helvick' said that figure is "bugging me".

Hi Helvick,
That number came straight from someone on the MER team.
I'm sure that there's room for error though.
Astro0

[fredk]

The latest navcam shows several changes in the tracks - the wind's been a-howlin' at Meridiani. And the shadows are much stronger now! (These views are less than half an hour apart local time.)

Sol 1224.
Sol 1231.

[helvick]

Thanks for the confirmation Astr0. I'm going to have to hope that this means that Tau was varying fairly dramatically that day. Otherwise I might have to accept I've been wrong. Oh The Shame!

[OWW]

According to this report on space.com the dust storm is still spreading.

http://www.space.com/scienceastronomy/070711_mars_dust.html
and
http://themis.asu.edu/dustmaps/

The enormous dust storm raging across Mars' southern half has begun to creep into the northern hemisphere as well, new satellite images reveal.

"This storm isn't as big or severe as the one in 2001," Bandfield said. "THEMIS and other orbiters can still see the surface, despite the continuing dust activity."

It's uncertain how long the current storm will last, but it probably won't disappear as quickly as it began. "Mars will remain dusty for at least a couple more months," Bandfield predicts.

Sounds like the rovers will remain power-starved for a Long time.

[Ant103]

Good eyes fredk. I'm going to make an animation to show this more evident

The Themis link is very good : hop! direct favourite

Edit : gif is finish.



The is little material disturbing, particulary just behind the low-gain antenna.

[Shaka]

According to this report on space.com the dust storm is still spreading.

Sounds like the rovers will remain power-starved for a Long time.

Especially long if they read the scale bars in reverse.
What's wrong with this picture? space.com figure

[fredk]

It occurs to me after comments in the Spirit thread that even though the local times are very similar in the two navcams I posted above, the tau has dropped from around 4 to around 3 so the lighting is less diffuse now. That should account for some of the changes visible in the tracks, but not all.

[fredk]

From Lemmon's dust devil page, Oppy is stable at tau = 2.9 as of sol 1231, but Spirit has climbed in the past few sols to tau = 2.8 on sol 1252, which is the highest Spirit has ever been.

I get the sense this could linger for some time. The fat lady has not yet sung.