[X] My Assistant

[Guest_Zvezdichko_*]

Hello,

According to the publication here:
http://www.space.com/missionlaunches/08053...ion-update.html


The glitch seems to be a short circuit in a filament in a part of the instrument that ionizes the vapors before they are sent to the detector...

Does that mean that it's directly related to the DSC oven?

[rlorenz]

Hello,

According to the publication here:
http://www.space.com/missionlaunches/08053...ion-update.html


The glitch seems to be a short circuit in a filament in a part of the instrument that ionizes the vapors before they are sent to the detector...

Does that mean that it's directly related to the DSC oven?

Doesnt sound like it. Remember each oven has its own heater and sense windings. This sounds like the filiament
to generate electrons to ionise the evolved gases before they pass into the quadrupole (i.e. part of the mass
spectrometer - the EGA part of TEGA)

Hopefully as the release says, they can get it up and running nonetheless. But even if the mass spec croaks
altogether there is a good chance of detecting water ice in the TA (thermal analyser, aka DSC - actually there
is a whole literature on how to run these things, whether it is a Differential Thermal Analyzer or a Differential
Scanning Calorimeter is largely an issue of software). Either way, you can detect the latent heat of melting
and evaporation.

[Skyrunner]

As I understand it the part that has shorted out is one of the two carrier gas ionizers.

The ovens vaporize the soil samples; these vapors are carried by a neutral carrier gas to the mass spectrometer. But before the carrier gas is fed over the sample it is charged then accelerated. The ionizer is needed to charge the gas so it can be be accelerated (like in an ion engine). Luckily there are two coils so when one is malfunctioning the other may be used instead. It seems to me that the team has some confidence that this is the case and full functionality can be restored.

[rlorenz]

As I understand it the part that has shorted out is one of the two carrier gas ionizers.

The ovens vaporize the soil samples; these vapors are carried by a neutral carrier gas to the mass spectrometer. But before the carrier gas is fed over the sample it is charged then accelerated.

No. ionization occurs in the mass spec. The carrier gas is neutral - remember the baking in the
ovens must be done under 'pressure'.

[Skyrunner]

Yeah, I should have known that. Next time I work with the gas chromatograph mass spectrometer we have at the faculty I shall pay more attention to the explanations of the lab technician.

As hoped it is working with the backup ionizing filament now.

[climber]

One TEGA image on sol 9 : http://phoenix.lpl.arizona.edu/images.php?...2662&cID=40
Looks like "something" is open now


Edit : labbeled Sol 9 but from sol 8

[mars loon]

One TEGA image on sol 9 : http://phoenix.lpl.arizona.edu/images.php?...2662&cID=40
Looks like "something" is open now

At todays (June 3) telecon, Peter discussed this. One door is fully open. The other is visibly and "unexpectedly" not fully open. they are working on it.

ken

[BrianL]

Are they planning to test all the doors to see if any more might have issues?

Brian

[bgarlick]

Do the doors need to also be able to close for proper TEGA functioning?
If not, I imagine the doors could be forced fully open by using a corner of the scoop if need be...

[Airbag]

Are they planning to test all the doors to see if any more might have issues?

I can't imagine so as then they would lose the ability to control what sample goes in what container - assuming the doors can not be closed again, or at least risking a door not being closed again.

Which brings up a point - can the TEGA doors also be closed again? The TEGA documentation I have read only mentions that the doors are solenoid operated, but does not say they are/can be closed prior to TEGA thermal analysis (which is not necessary since each oven seals itself).

Let's say the doors can close - but would the dirt that was not filtered through and vibrated off the screen not prevent them from doing so anyway?

But say they can not close - then could a misplaced clump of dirt not prevent the neighboring door from opening, if said clump of Mars' finest dirt was deposited along the hinges of two adjoining doors, especially if one of those doors was at a convenient angle for the dirt to slide down towards the hinge...?

Well, we'll see soon enough!

Airbag

[rlorenz]

Which brings up a point - can the TEGA doors also be closed again? The TEGA documentation I have read only mentions that the doors are solenoid operated, but does not say they are/can be closed prior to TEGA thermal analysis (which is not necessary since each oven seals itself).
......
But say they can not close - then could a misplaced clump of dirt not prevent the neighboring door from opening, if said clump of Mars' finest dirt was deposited along the hinges of two adjoining doors, especially if one of those doors was at a convenient angle for the dirt to slide down towards the hinge...?

IIRC the doors are spring-loaded, and *released* by solenoid. No closure possible. (Opening is inhibited
by a memory-metal clutch thingy to prevent launch vibration popping it open)

Obviously, as you say, door closure is not needed for the analysis, as the oven seal takes care of isolating
the sample from the atmosphere.

As for dirt - it would need an awful lot of dirt to jam up an adjacent door. Getting enough sample is
considered more of a concern than getting too much.

[Sandro]

Hi together

I just had an short idea on a possible fix for the not fully open door. Although they can operate with the door not fully open (as far as I understood) I think it could be possible to open the door with help of the robot arm.

The doors are spring loaded and if they would move the arm slightly from left to the right (on this picture http://phoenix.lpl.arizona.edu/images.php?...2662&cID=40 ) over the not fully open door, we could press the door again down and hope that after the pass of the arm the springs will push the door fully open.

What are your thoughts about that option?

Regards,
Sandro

[MahFL]

I think the safest thing to do is just use the oven as it is, as they say the door is open enough.

[djellison]

A thermal day-night cycle may well help it deploy further as well. But active intervention would be un-necessary

Doug

[bgarlick]

The screen behind the TEGA doors looks very fine meshed and the soil looks very clumpy. I would not be surprised if they have a real hard
time getting any material through that screen. Is there a way for them to tell how much material is in the oven before closing the oven and starting the baking?

[nilstycho]

Whenever something gets stuck on a spacecraft, the two options available seem to be (1) jiggle it and (2) heat it. I'm imagining a spacecraft with lots of little peizoelectric-cum-resisting pads that can just vibrate and heat lots of things all over the spacecraft. This is an evolution from an earlier plan whereby each orbiter would have a micro helperbot that was equipped with (1) a hammer.

[MahFL]

The screen behind the TEGA doors looks very fine meshed and the soil looks very clumpy. I would not be surprised if they have a real hard
time getting any material through that screen. Is there a way for them to tell how much material is in the oven before closing the oven and starting the baking?

I think they would have thought about this before they launched it..........

[bgarlick]

I think they would have thought about this before they launched it..........

Note that they did do a second dig-n-dump because they were caught off guard by how sticky/clumpy the first scoop was.
Maybe the soil's properties are not exactly what they were expecting...

[nprev]

they were caught off guard by how sticky/clumpy the first scoop was.

Or electrostatically clingy? Just a thought; water really is practically a mineral where Phoenix is.

[Airbag]

I'm still kind of surprised that they did not use up one of the TEGA ovens for a "contingency" sample. On the Apollo missions that is pretty much the first thing they did on the first EVA of each mission - take a contingency sample of soil and rocks right outside the LEM, whatever was there. Then at least in case some emergency arises you have *some* samples.

If I were in charge I'd have dumped that very first scoop into a TEGA oven. Still have 7 ovens left, which is more than MECA can handle anyway, and what if the RA suddenly stops working...?

Airbag

[Tom Tamlyn]

equipped with (1) a hammer.

What a relative of mine, an engineer, likes to refer to as "the instrument of persuasion."

TTT

[JRehling]

On the other hand, what if the first use of the RA were the event that made it fail and we did so retrieving an uninteresting sample instead of an interesting one. Risk is a complex thing.

[glennwsmith]

I like Sandro's idea, after it has had time to open on its own.

[rlorenz]

Whenever something gets stuck on a spacecraft, the two options available seem to be (1) jiggle it and (2) heat it. I'm imagining a spacecraft with lots of little peizoelectric-cum-resisting pads that can just vibrate and heat lots of things all over the spacecraft. This is an evolution from an earlier plan whereby each orbiter would have a micro helperbot that was equipped with (1) a hammer.

There is an actuator that vibrates the funnel to encourage material to flow down into the oven. You could think
of it as a hammer...

[centsworth_II]

There is an actuator that vibrates the funnel to encourage material to flow down into the oven.

I wonder if that vibration extends to the screen, encouraging loosely clumped material to break up and fall through.

[Airbag]

On the other hand, what if the first use of the RA were the event that made it fail and we did so retrieving an uninteresting sample instead of an interesting one. Risk is a complex thing.

That may be, but from many reports it seems that it is the daily temperature variations that are the main source of unexpected component failures. So the longer you wait before doing something, the bigger the chance something will break.

Airbag

[rlorenz]

Is there a way for them to tell how much material is in the oven before closing the oven and starting the baking?

Not in as quantitative a way as one would want (it isnt a ThermoGravimetric Analyser)

There is an LED/photodiode 'oven full indicator' that shows if soil has backed up in
the load pipe - typically because the oven is full (duh). Transient signals from that may
give an indication of stuff drizzling into the oven during loading before it gets full.

A minor role I have associated with the TEGA team (I worked on TEGA-1 on MPL) on
which I did some lab testing while still in Arizona is on seeing whether the photodiode
data can give a sample mass estimate.

ans : maybe.

(a post-hoc mass estimate can also be had from the DSC data which indicates the heat capacity of the
sample, but that is also somewhat sample-dependent)

[ollopa]

Ironically, it is a "hammer" that appears to be causing the filament problem, and which could also be used as an "instrument of persuasion" in extremis.

There is a solenoid on the atmospheric gas inlet valve that gives a hefty kick when it opens and closes. The short-circuit apparently comes and goes with the operation of this valve. If the back-up filament were to fail, the fall-back would be to operate the inlet valve until the circuit closes on the primary unit and then leave it. Right now, I believe they're not operating the inlet valve - IIRC they are content to sample the atmosphere by opening the cell door, which is less optimal than venting through a small valve.

[Skyrunner]

I was wondering the accuracy of the samples (on both TEGA and MECA). Obviously the payload engineers went through great lengths to make the instruments as accurate as possible. But what makes me wonder is the temperature gradient. The soil is much colder than the lander deck (and instruments). We now this from METs temperature sensors as well as engineering calculations. Small differences in temperature could (at least in theory) lead to out gassing in the sample so that immediately after the sample is scooped up it could start out gassing. After the sample is dumped in the instrument of choice (before closing its lid) or when the arm is above deck, it heats up even more, encouraging more out gassing. Yes, the out gassing shouldn't be that much but still....it make me wonder about the accuracy and the precautions taken.

Wasn't this a concern for Viking as well?

[volcanopele]

What a relative of mine, an engineer, likes to refer to as "the instrument of persuasion."

Or as my old AP Physics teacher from high school would say, "If at first you don't succeed, use a hammer."

[Skyrunner]

Or as my old AP Physics teacher from high school would say, "If at first you don't succeed, use a hammer."

Or as the first tenet in mechanical engineering goes:
"If the brute force fails to work,
try using more of it"

[djellison]

Mythbusters
"With enough lubrication, we can do anything"



Doug

[Littlebit]

I was wondering the accuracy of the samples (on both TEGA and MECA). Obviously the payload engineers went through great lengths to make the instruments as accurate as possible. But what makes me wonder is the temperature gradient. The soil is much colder than the lander deck (and instruments). We now this from METs temperature sensors as well as engineering calculations. Small differences in temperature could (at least in theory) lead to out gassing in the sample so that immediately after the sample is scooped up it could start out gassing. After the sample is dumped in the instrument of choice (before closing its lid) or when the arm is above deck, it heats up even more, encouraging more out gassing. Yes, the out gassing shouldn't be that much but still....it make me wonder about the accuracy and the precautions taken.

Soil sampling is rarely entirely representive. In the Martian polar climes, where there are radical swings in temperature and soil shifting due to growth and shrinkage of the polar cap, you would expect a dynamic stability - ultra light molecules are gone, water ammonia and such just below the surface will sublime, but not terribly quickly at these temperatures and pressures. The samples should be highly representative, maybe off a few percent in the most volatile chemicals found.

[ilbasso]

Mythbusters
"With enough lubrication, we can do anything"



Doug

Anybody remember the Firesign Theatre and Fudd's First Law of Opposition? "If you push something hard enough, it will fall over."

[mike]

What about a flat plate resting long axes parallel to the eternally flat ground.. on the planet Flatia.. I suppose you could push it so hard it moves into space, at which point it will eventually fall onto something.. but it might fall onto an evil entity of some kind, like say an anti-happiness consortium

[Guest_Zvezdichko_*]

http://phoenix.lpl.arizona.edu/06_07_pr.php - sample released, "but the instrument did not confirm that any of the sample passed through the screen."

[Harder]

This first sample is "topsoil" where the 1 mm mesh screen can be expected to pass thru the finer material - or perhaps not, as we now seem to find out.

But to expect that ice-type matl scraped from deeper trenches will pass thru such a fine mesh screen seems completely impossible. I´m really flabbergasted to learn about the existence of this fine mesh screen today. Surely the design team has thought through the scenario of delivering ice and created a couple of bins without a screen? Take the test by getting a scoop of sorbet ice from your deepfreezer - the only way to get scraps of sorbet ice through any screen, no matter the mesh size, is by melting! But on Mars the sublimation will happen first.

Too pessimistric a view? I really, sincerely hope I overlook something here!

[ugordan]

Too pessimistric a view? I really, sincerely hope I overlook something here!

I was under the impression they're primarily interested in stuff potentially mixed in (dissolved?) in the ice, not ice per se. Even if ice sublimates away (and it only sublimates really fast when you have isolated small particles of ice, not loads of them), the other stuff will be left behind.

[Guest_Sunspot_*]

Oh Dear, things don't seem to be going too well.

[01101001]

But to expect that ice-type matl scraped from deeper trenches will pass thru such a fine mesh screen seems completely impossible.

How large to you expect the rasped ice particles to be?

RASP SAMPLE ACQUISITION ON THE PHOENIX MARS SCOUT MISSION (PDF)

The rasping operation powderizes materials while
it is cutting them free. In a few seconds and in a single
operation, rasp systems cut away strong materials,
process them to sizes that are instrument-ingestible,
and capture them in a catch container.
[...]
Conclusions: Rasping with the current ISAD RASP
bit design can remove a significant fraction of H2O in
permafrost samples. This is on top of passive sublimation
that takes place as the sample is transferred to the
instruments to be analyzed.

But the fraction looked to be 10 to 30 percent depending on weather.

[Harder]

Thanks for this info. It states that the rasp produces cuttings that are instrument-digestible. I can imagine that ice/permafrost as hard as stone will indeed be rasped into finer pieces which are immediately suitable to pass through the funnel of the TEGA. So why install a fine mesh screen in the first place, especialy since icy particles have some tendency to bind together and won´t pass at all thru a strainer just by the force of gravity?

Perhaps my misunderstanding is because icy particles/crystals on earth have some liquid water which creates these coagulation effects (like snow flakes) whereas on Mars liquid water is not forming at all. Even here there is a shadow of a doubt, due to the heat imparted by the rasp which might create temporary softening/melting of ice in rasp cuttings.

[bgarlick]

The screen behind the TEGA doors looks very fine meshed and the soil looks very clumpy. I would not be surprised if they have a real hard
time getting any material through that screen. Is there a way for them to tell how much material is in the oven before closing the oven and starting the baking?

Darn! It looks like my concern back on the 4th was not completely unfounded...
I wonder if they have the dexterity to use the RA scoop to manually 'smoosh' some of the soil through the TEGA screen, or at least press down on the soil on the screen with the scoop while the shakers are activated.

[brianc]

Darn! It looks like my concern back on the 4th was not completely unfounded...
I wonder if they have the dexterity to use the RA scoop to manually 'smoosh' some of the soil through the TEGA screen, or at least press down on the soil on the screen with the scoop while the shakers are activated.

A wee tap with the scoop on the end of the arm should do the trick. My wealth of DIY projects leaves with me with the conclusion that there are few jobs that can't be completed with the aid of a hammer and screwdriver and the scoop looks like the sort of thing I would use as a hammer, actually my dad (god rest his soul) may well have used the scoop edge as a screwdriver substitute, I seem to recall him using mother's cutlery as proxy-screwdrivers !

[MahFL]

Oh oh, lots of head scratching at UA.

[Stu]

Well, head-scratching is good, you know? Doesn't do to take success for granted, and Mars takes a perverse delight in making us work for the knowledge we gather there. This is just one more thing to work out, isn't it? This spacecraft has been tested to within an inch of its life, but they couldn't predict every possible problem. I'm sure they'll figure something out.

If all else fails, Phoenix's passenger can pat the dirt with a paw, after his heroic efforts removing the bio-barrier earlier in the mission...

(No, seriously... packing a cat into a Faberge egg and ejecting it from Phoenix??... who thought that up? And where can I buy some of whatever they were on when they did? )

[belleraphon1]

Here is where litter box skills will come in handy. Yes, this may a job for Steve the Cat!!!!

Seriously.... I believe there were similar issues on Viking, and that team worked it through. I am sure this team can do the same.

Does anyone know if the scoop arm is capable of actually touching the TEGA ports? I am not sure if it can reach down that far.

Craig

[ngunn]

Mars people please - I need some help with dismissing what is probably a daft idea. In the presence of salts it is possible for a wet soil to refuse to dry out completely; it just stays sticky. Is it possible for carbon dioxide ice to be saline, in the way that water ice can? Could that make it resist sublimation? For water, salt widens the gap between freezing and boiling, favouring the liquid state. Is it possible to imagine 'saline carbon dioxide' having a liquid phase on Mars, even transiently, that might make the soil sticky? I know. It's horrible. Shoot it down quickly please.

[deglr6328]

The liquid phase of CO2 is forbidden below 5 bar.

[ngunn]

The liquid phase of CO2 is forbidden below 5 bar.

That's a very good start! But I need more to dismiss the idea entirely. We don't know what chemical games CO2 engages in when it is a constituent of the soil.

I suppose we also have to consider aqueous brines with excessively low melting points for the cause of the stickiness. Is there such a thing as a H2O:CO2:chloride brine?

[deglr6328]

Ionic salts are insoluble in liquid CO2 because it's non-polar and the solubility of CO2 in water at low pressure is insufficient to have an appreciable freezing point depression effect.

[helvick]

Is there such a thing as a H2O:CO2:chloride brine?

Seltzer..

[elakdawalla]

So why install a fine mesh screen in the first place, especialy since icy particles have some tendency to bind together and won´t pass at all thru a strainer just by the force of gravity?

There's a very good reason: the business end of TEGA, the oven itself, is a tiny quartz vial only a millimeter in diameter. If they let anything bigger into the doors, it would block the opening of the oven, and you'd get no sample.

--Emily

[deglr6328]

Mightn't we expect the MARDI microphone to be used sooner than expected now for trobleshooting, ie. to listen for TEGA mesh vibration?

[Reed]

Is there a diagram or detailed description of the layout of TEGA anywhere ? A quick google didn't turn up much beyond this page http://planetary.chem.tufts.edu/Phoenix/th...as_analyzer.htm

[Aussie]

but they couldn't predict every possible problem. I'm sure they'll figure something out.

I'm sure they will Stu. The MER team proved their innovation time and again. But Phoenix planners must have known that martian soil has clumping tendancies since Spirit took the close up on 18 January 2004. So they had a heads up and plenty of time to consider the implications of putting a fine mesh over the oven (although obviously that filter is required). With respect to rasped ice I would anticipate that they would have tested the theory in a Martian temperature/pressure simulated environment to make sure that the rasped ice didn't bond back together. They would have..wouldn't they?

[SickNick]

Or as my old AP Physics teacher from high school would say, "If at first you don't succeed, use a hammer."

Don't FORCE it, just use a bigger hammer...

[SickNick]

Mars people please - I need some help with dismissing what is probably a daft idea. In the presence of salts it is possible for a wet soil to refuse to dry out completely; it just stays sticky. Is it possible for carbon dioxide ice to be saline, in the way that water ice can? Could that make it resist sublimation? For water, salt widens the gap between freezing and boiling, favouring the liquid state. Is it possible to imagine 'saline carbon dioxide' having a liquid phase on Mars, even transiently, that might make the soil sticky? I know. It's horrible. Shoot it down quickly please.

The behaviour of CO2-H2O mixtures is well understood over a wide range of temperatures and pressures. At Earth-normal conditions, CO2 dissolves slightly in water to form carbonated beverages and acid volcanic/mineral water. Solubility is better at higher pressure and lower temperature. At low temperature, a joint ice (Clathrate) is formed. This can form at up to 10C (above the melting point of pure water). Again, pressure favours clathrate formation.

it is not clear wheter CO2 clathrates are stable at mars near-surface conditions, but there is almost certainly SOME clathrates in the pole caps (On earth, the polar ice contains small amounts of Nitrogen, oxygen, and CO2 clathrates because trapped gas in snow is not entirely expelled from recrystallised ice. On Earth it's a curiosity. On Mars, it *might* be important, or it might not. (If the poles had a substantial CO2 clathrate component, they could be trapping a significant fraction of a whole atmosphere's woth of CO2, for example.

Excess CO2 *can* exist as a liquid at depth, above 5.2 bars and below 30C. This is unproven, but fun to speculate on...

[dvandorn]

Don't FORCE it, just use a bigger hammer...

But just remember -- when the only tool you have is a hammer, most everything begins looking like a nail...



-the other Doug

[deglr6328]

The behaviour of CO2-H2O mixtures is well understood over a wide range of temperatures and pressures. ..........

Excess CO2 *can* exist as a liquid at depth, above 5.2 bars and below 30C. This is unproven, but fun to speculate on...
=====================================
Nick Hoffman Mars Specialist
White Mars Research Unit

My heavens! It never ceases to amaze me the actual scientists and engineers who pop up on this site, it's fantastic. Though, I see that almost all of your posts were made 4 years ago Nick and so I have to ask; your 'no-liquid-water' "white Mars" liquid CO2 only theory, if it hasn't been well and truly demolished by the findings of the MER's over the past several years must be hanging by the thinnest, most gossamer thread imaginable. Are you prepared to abandon it as the evidence now appears to demand that you must?

[gallen_53]

Or electrostatically clingy? Just a thought; water really is practically a mineral where Phoenix is.

An electrostatic clinging mechanism would be my guess as well.

I suggest that the guys at JPL smear a regolith sample flat on a metal surface of the vehicle and let it sun a bit. Then scrape it up and deposit it into the TEGA.

Another approach would be to scoop up some regolith, jiggle the sample, orient the scoop so the sample gets lots of sunlight, jiggle some more, repeat several times and then deposit the sample into the TEGA.

The trick is to encourage electrostatic discharge. Short wavelength UV reaches the Martian surface and that should accelerate electrostatic discharge if the sample is properly exposed.

[ngunn]

Excellent replies from the chemists as I had hoped. I've no objection to the electrostatic-sticky explanation, but nevertheless I persist with the thought that there could be a damp-sticky component (possibly a seasonal transient one) in this soil. Abandoning foolhardy attempts to guess myself what that might possibly be I ask the experts again this wider question. Are there any plausible candidates?

[Tman]

Could it be that the behavior of this sample is affected by the soil that was blown away (and probably melted too) when Phoenix landed?

[Aussie]

An electrostatic clinging mechanism would be my guess as well...... Short wavelength UV reaches the Martian surface and that should accelerate electrostatic discharge if the sample is properly exposed.

But the dust deposited on the MER solar panels clumps? So perhaps the electrostatic explanation is not the answer. I think ngunn has asked an extremely valid question. Is there a cementation process here and if so what?

[SickNick]

But the dust deposited on the MER solar panels clumps? So perhaps the electrostatic explanation is not the answer. I think ngunn has asked an extremely valid question. Is there a cementation process here and if so what?

I don't think there is a "need" for an electrostatic clumping mechanism. The Mars soil is basically rock flour, and extremely fine gained powders (or powders with a fine component) are notorious for clumping. Perhaps it is caused by Van-der-Waals forces between exposed and damaged mineral surfaces in the very fine grains, but it is a genuine and relatively common behaviour. Wheat flour behaves just like this, even though it is compositionally very different.

How to deal with it? More difficult. A small mechanical pulveriser? A forced seive? None of these are built into the TEGA design. Maybe the soil sample can be pushed against the filter grid by the remote arm, but maybe that would just pack it worse?

Maybe the next sample can be dumped from higher up so that it gets more dispersed as it falls? SOme more dump-and-drop trials would be in order, I think. with careful photos of the clumping as the regolith falls/arrives.

maybe the sample needs to be smaller?

Time for some careful trial and error, and some practice with an appropriate physical simulant on Earth...

[Guest_Zvezdichko_*]

Hello, I have a question which may sounds a bit silly, but anyway. At Uni we study that a soil is a substance which has three components: the mineral component (it's basically the underlying rock), the organic component (humus, peptones and so on), and gas component (CO2, nitrogen...). The Martian soil is obviously lacking the organic component (if Gas-Chromatograph aboard Vikings gave correct results). We are still waiting the results from the problematic TEGA which has some advances (slow heating etc). So why call it "soil"? In the Eastern block we call it just "grunt".

[djellison]

So why call it "soil"?

Because that's the lazy thing to call it. Fines, regolith, whatever geologically accurate term you elect to use is fine - but 'common' english means that soil is the 'stuff' on the ground. It's a point that has been at some of the press confs.

[Guest_Zvezdichko_*]

Once again, thank you, Doug. In the end MECA and TEGA may prove that the Martian soil is more Earth-like, with nearly neutral pH, organic material and normal concentration of salts.

[SickNick]

Once again, thank you, Doug. In the end MECA and TEGA may prove that the Martian soil is more Earth-like, with nearly neutral pH, organic material and normal concentration of salts.

let's see what it *does* prove, rather than pushing our own speculative agendas.

The important thing with planetary missions is to wait.

See all the data, and think what the hell it means. It's never what we expected, or imagined, or hoped. Sometimes a single image or data point is a breakthrough. other times it takes an accumulation of images and data to help us understand what's going on.

I'm itching for TEGA data. Let's all try to be patient while our good friends on the mission team work out how to get the data, despite any obstacles that may arise.

[Guest_Zvezdichko_*]

I apologise to you then. This was my natural desire, my expectations, my heart is with that mission.

[glennwsmith]

A tip o' the hat to bgarlick for his prediction, on June 4, re difficulty of getting material through the screen. Interesting, that much of the challenge of space exploration will involve what could be referred to as "fuzzy" engineering, ie, the problem of lunar dust. But the Phoenix team has a lot of options, and they will figure it out!

[Sputnik]

Wouldn't a high frequency vibrator between the bottom of the receptacle and the oven itself be enough to shake some particles from the sample, into the oven?

[gallen_53]

IMaybe the next sample can be dumped from higher up so that it gets more dispersed as it falls? SOme more dump-and-drop trials would be in order, I think. with careful photos of the clumping as the regolith falls/arrives.

That's the ticket! Just slowly pour it in from higher up. It'll be a bit messy but should do the trick.

[gallen_53]

Sushil Atreya (a professor at the University of Michigan) has written some papers about the accumulation of electrostatic charge on Martian dust. This publications list at http://www-personal.umich.edu/~atreya/s_publications.html by Prof. Atreya covers many diverse topics in planetary science, provides PDF links and is very interesting. I suspect Prof. Atreya would have predicted this clumping problem if anyone had bothered to ask him.

[JRehling]

Could it be that the behavior of this sample is affected by the soil that was blown away (and probably melted too) when Phoenix landed?

There was definitely some alteration of the surface -- the key answer would be, what is the displacement of native surface material as a function of distance from Ground Zero? We can make 3D micro-topo maps of the vicinity and, with the sound assumption that there was nothing special about the landing site before Phoenix dropped out of the sky, measure the local effect. It seems to be something like 6 cm of displacement at Ground Zero. The stain shown by MRO probably corresponds to the boundary of a VERY slight alteration of the surface (akin to dust devil tracks or less -- the backshell made a stain a significant fraction of the same size).

I suspect that the alteration where the arm dug first is on millimeter scales and moreover consisted largely of removal of dust rather than alteration of the stuff that's left.

By definition, the post-landing surface consists of the surface where the force of the engines was too weak to move any more material. So I think if the material's failing to fall through the only difference owing to the engines is that there might have been a VERY fine layer of dust that would have fallen through and was instead blown away. If this stuff that was collected had been powdery before, it would have blown away, too.

I highly doubt that the stuff here was melted by the rockets. It takes an awful lot of heat to get that cold of ice up to 0C and much more to melt it. The moment of landing was pretty quick, and exhaust would cool off incredibly fast in that environment.

[Guest_Sunspot_*]

Has there been any update on the TEGA problem?

[akuo]

Twitter says:

Goal Sunday was to shake the screen to help soil particles fall into the TEGA oven. Downlinking data o'nite for team to see the result.

[Stu]

Hey, Doug, if all else fails, they could always ask Lewis Hamilton to give Phoenix a gentle nudge...

[djellison]

You think you're funny... you THINK you're funny.

Actually - that is kind of funny. Hamilton could nudge it one way, Rosberg the other

[akuo]

A sol 14 image of TEGA has appeared. There is some shifting of soil over the next sample doors, at least:
http://phoenix.lpl.arizona.edu/images/gallery/lg_3567.jpg
Earlier image:
http://phoenix.lpl.arizona.edu/images/gallery/lg_3304.jpg

Edit: More images:
http://phoenix.lpl.arizona.edu/images/gallery/lg_3568.jpg
http://phoenix.lpl.arizona.edu/images/gallery/lg_3571.jpg
http://phoenix.lpl.arizona.edu/images/gallery/lg_3572.jpg
http://phoenix.lpl.arizona.edu/images/gallery/lg_3573.jpg

I'd be surprised if there wasn't a sample acquired now :-)

[jmknapp]

I highly doubt that the stuff here was melted by the rockets. It takes an awful lot of heat to get that cold of ice up to 0C and much more to melt it. The moment of landing was pretty quick, and exhaust would cool off incredibly fast in that environment.

The ice could sublimate though, right? Phoenix landed around 5pm local time so the temperature probably would have been near the max -30C.

A paper On the sublimation of ice particles on the surface of Mars states:

During the Phoenix mission to Mars it is planned that a Robotic
Arm will be used to obtain samples of sub-surface ice
and deliver these to analysis instruments. The process may take
several hours and there is a concern that, if the samples are not
treated appropriately, significant sublimation could take place.
Cloud physics modelling of sublimation from a single ice
particle suggests that the half-life of 1-mm-diameter particles,
even with no ventilation or solar radiation, would be less than
3 h, even at 223 K [-50C] and that smaller particles or warmer temperatures
would exacerbate the problem. Mars chamber experiments
with isolated particles freely exposed on a surface confirmed
this prediction. The procedure in Phoenix will however be to
collect a small pile of a mixture of ice chips and dust. We find
that the sublimation rate from this will be lower, especially if
the pile is a mix of ice and dust and can be kept cold and shaded.

...

(1) Single small ice particles, or loosely scattered particles are
liable to sublimate rapidly in the atmospheric conditions
anticipated during the Phoenix mission.
(2) When collected together in a pile, the sublimation rate appears
to depend primarily on surface area rather than total
mass. ...
(3) Temperature is THE critical parameter and ice samples collected
during the Phoenix mission must be kept as cold as
possible, and in the shade, while awaiting analysis.
(4) Mixtures of ice particles and dust sublimate less rapidly
than pure ice at the same temperature and in a similar container.
The lowest sublimation rates at temperatures near
−30 ◦C (CSIL, Run 14) occurred for mixtures of ice particles
with very fine dust.
(5) Actual sublimation rates on Mars may be significantly
larger in the presence of wind speeds that exceed a few meters
per second.

[MahFL]

I'd be surprised if there wasn't a sample acquired now :-)

I am not convinced myself.

Also the next set of doors are well covered in dirt, as the first set did not open correctly with out anything ontop of them it does not bode well for the future. I wonder if the team had tested this situation out, I'd be astonished if they had not.

[ugordan]

Hmmm... I wonder how much (if any) of the soil fell through the mesh as opposed to just consolidating and sliding downward along the mesh? It doesn't look like the soil level was depressed after the vibration, at least not noticeably. The images don't look very promising to me. Hopefully some of the smaller grains did manage to get through...

[MahFL]

I still maintain they poured way too much soil onto that oven opening.

[Stu]

I can't make out much "settling" or shifting either... fingers crossed that some small grains managed to sift out of the underlying crud...

I was very surprised to learn just how tiny these TEGA ovens actually are! There's a good YouTube clip here, and you can see the ovens at 6:23. Tiny!!

[ugordan]

On the brighter side, even if there was soil deposited into the oven, that small an amount wouldn't be readily obvious to the RAC. Fingers crossed.

[centsworth_II]

I wonder why they started with the uppermost oven. If they had started at the bottom, excess dirt would fall away from the yet unused oven doors. As it is, if they continue from high to low, there will be quite a pile built up by the time they get to the lowest.

.... or, is the TEGA shuttered cover horizontal and only looks tilted in the image?

[djellison]

The ovens are side by side, not one above the other. That oven is the same level as the other 3 on that side, and the four on this side.

Doug

[centsworth_II]

The ovens are side by side, not one above the other.

Ah, now ugordan's movie makes sense to me!

(I forgot, the shape is like a gable roof.)

[djellison]

Yeah - it's a very very expensive, but small, barn conversion

http://phoenix.lpl.arizona.edu/images/gallery/lg_99.jpg

[centsworth_II]

Yeah - it's a very very expensive, but small, barn conversion

It's funny seeing that salt shaker to the right in the image you link. For depositing test samples? I can't imagine the test bench doubles as a lunch room counter!

[tuvas]

Poor TEGA... It just doesn't seem to be working quite as intended... I sure hope they can get all of the problems resolved...

[centsworth_II]

Poor TEGA... It just doesn't seem to be working quite as intended... I sure hope they can get all of the problems resolved...

I hope you're not saying this based on something you've heard about the second attempt to get sample into the oven.

[MahFL]

Yeah - it's a very very expensive, but small, barn conversion

http://phoenix.lpl.arizona.edu/images/gallery/lg_99.jpg

Hey did ya'll notice the salt shaker in that picture ?

[Stu]

I hope you're not saying this based on something you've heard about the second attempt to get sample into the oven.

Oh surely not. I can't imagine anyone here who'd be so cruel as to drop a hint about a development they've heard about but can't share with the world yet -

Oh hello Jason, didn't see you there...!

[jmknapp]

Is a press conference scheduled today? Seems like there's a lot of fodder for questions, given that TEGA is kind of the central instrument of this mission, such that "Poor TEGA" = "Poor Phoenix."

[Stu]

Yep...

Media Update
NASA and the University of Arizona, Tucson, will hold a media teleconference at 11 a.m. PDT (2 p.m. EDT) on Monday, June 9, to report on the latest news from NASA's Phoenix Mars Lander mission.

[Guest_Sunspot_*]

How many of the original science objectives can be met without TEGA?

[ugordan]

Whoa, people... Getting a bit negative, aren't we?

[Stu]

I was just thinking that... come on guys, first sample dump, first oven, first everything. That's why there are more than one on there; it was very unlikely everything would go perfectly the first time. I reckon the Phoenix team reading this need our support and encouragement now. Keep at it!

Edit: interesting article here...

[MahFL]

There are plenty of positive things about Phoenix of course. We have colour and 3d pics of the northern tundra. Pretty sure we see ice under the lander. Temperatures, pressures and wind direction. Microscope views of the dust/dirt. I am sure I missed a few things too.