NASA's Phoenix Finally Fills Oven

JoeRobe writes "Phoenix has successfully filled oven #4 of the Thermal and Evolved-Gas Analyzer instrument (TEGA). They have spent several days now vibrating the screen above the oven, trying to get a significant amount of soil sample into it. From the article: '[T]he oven might have filled because of the cumulative effects of all the vibrating, or because of changes in the soil's cohesiveness as it sat for days on the top of the screen.' Either way, this is the first step toward getting some interesting data from this instrument."

Comments

Cookies

[LeoDavinci578]

Who wants cookies?

Re:Cookies

[Mr2cents]

Just imagine that in a few days from now, the news headline could be "NASA cooks the first extraterrestial life - tastes like chicken".

invalidate the tests

[phrostie]

couldn't this invalidate the tests.

it seems to me that the clumps could be caused by the very ice we are looking for.
by screening it out, the samples won't be representative of the soil

Re:invalidate the tests

[LBArrettAnderson]

From my limited understanding of the properties of H2O on mars, I would imagine that letting a clump of dirt sit up above the soil would cause the ice to sublime after being directly exposed to sunlight. Anyone know if this is possible? Obviously they aren't going to get a false positive... but a false negative seems likely (although I'm sure that they will know this if it happens to be the case, and will try again to find water).

Re:invalidate the tests

[osu-neko]

couldn't this invalidate the tests.

I don't think so. What would they be testing for that would be invalidated by this? If they find presence of life, or evidence of past life, the fact that they screened something out doesn't invalidate what they found in what was left. If they fail to find anything like that, there's no valid conclusion that could be drawn in any case (absence of evidence is not evidence of absence), so a conclusion of "there's no life and never was" would be invalid regardless of whether parts of the sample were screened out or not.

In short, if it's a partial sample, it reduces the odds of success, but does not invalidate any result.

Re:invalidate the tests

[osu-neko]

Flawed data is better than no data. Right?

No. But that's not the issue here. What we're talking about here is getting less data than we'd like (because of what was excluded from the sample). Data is not "flawed" for being a smaller quantity, it's just, less. Some data is better than no data at all.

Re:invalidate the tests

[osu-neko]

There's no such thing as a "false negative" for the kind of tests they're doing. They're not conducting the kinds of experiments that would falsify a theory. The only results possible from the tests they're doing are "confirmed" or "failed to confirm" (and nothing much can be concluded from the latter in any case).

Re:invalidate the tests

[jessemerriman]

(absence of evidence is not evidence of absence)

Yes, it is:

Absence of proof is not proof of absence. In logic, A->B, "A implies B", is not equivalent to ~A->~B, "not-A implies not-B".

But in probability theory, absence of evidence is always evidence of absence. If E is a binary event and P(H|E) > P(H), "seeing E increases the probability of H"; then P(H|~E) < P(H), "failure to observe E decreases the probability of H". P(H) is a weighted mix of P(H|E) and P(H|~E), and necessarily lies between the two.

(from this Overcoming Bias post)

Re:invalidate the tests

[cetitau]

I don't want to sound like an expert in this field but I don't understand this response. This science doesn't look for life. Here it's looking for some specific chemical content in the oven at the conclusion of the test. If clumpiness was a result of soil mixed with frozen volatiles, i.e. soil particles stuck together by water or other ices, then evaporation of the volatiles over these days of shaking could certainly alter the outcome. I believe none of these tests are designed to prove or disprove the existance of life on Mars, only to produce results that could indicate or contraindicate the possibility that life could exist or could have existed at some time. The only sure proof would be a video of a drunk Martian Cubs fan stagering home after yet another loss at the park.

Re:invalidate the tests

[SiliconEntity]

This is just the first test. At this point, Phoenix is supposed to be testing the soil, not the ice. Later, they are going to dig down into the ice. They have a special drill-like object on the digging tool which will drill into the ice and produce fine shavings. These shavings will then be scooped up and dumped into the oven. But that will come later, first they are testing the soil. This is what has been a problem so far, it's good that they have managed to make progress with it.

Re:invalidate the tests

[profplump]

Why isn't "flawed data" at least sometimes the same as "some data" and therefore better than "no data"?

For example, what if you had a rain meter that leaked -- you couldn't accurately determine accumulation, and you couldn't conclusively ascertain that no water had fallen just because it was empty, but if the meter read 1.28" when you looked at it you could conclude that at least 1.28" of water had fallen since last time the collector was drained. The 1.28" reading would flawed, but the device would still provide the same sort of data it was designed to collect; so long as your understand the nature of the "flaw" in your data it is still generally useful.

Re:invalidate the tests

[Anonymous Coward]

It is a real concern, but it isn't a mistake.

The JPL engineers who designed it knew from the start that certain compounds, including water ice, would begin to sublimate once the soil was disturbed. For this reason, they wanted to get the samples into the chamber relatively quickly. It is very likely that the 3-4 day delay caused some loss of volatiles. It doesn't completely invalidate this sample because it's unlikely that all the ice sublimated, and water isn't the only thing they're looking for.

Also, there are 7 other chambers in this instrument, and they believe they've figured out how to avoid this trouble in the future.

They did test the aparatus pretty thoroughly on earth, but the soil properties ended up being quite a bit different from what they expected. No mission before has handled soil in quite the way Phoenix does, and the soil at the north pole may well be different from that in locations where previous landers have touched down.

Re:invalidate the tests

[antic]

"If they find presence of life..." ...let's cook it!

Re:invalidate the tests

[Anonymous Coward]

Phase diagram of water: http://www.lsbu.ac.uk/water/phase.html

Note the portion where solid and vapor phases are adjacent with no liquid phase in between (sublimation/deposition).

Re:invalidate the tests

[petermgreen]

Water doesn't sublime.
It does if the pressure is low enough, I think on mars there would be a liquid phase though it would be much much narrower than on earth such that it would be almost too narrow to notice.

Re:invalidate the tests

[tweak13]

Water Ice sublimes even in the earth's atmosphere. Ever wonder why ice cubes shrink after they've been in a freezer for a really long time? It's also the reason that all the ice will "melt" off your car if you expose it to the sun, even if it's below freezing out. Freezer burn on your food is also caused by sublimation. So yes, water ice does sublime, and in low pressures would probably do so even more.

Re:invalidate the tests

[eonlabs]

What I'm sure the 'grandparent' article is referring to as a false negative is that if there were water (ice) in the original sample when it was taken, there's a risk that several days vibrating it in under low atmospheric pressure may cause it to evaporate. If it's a small enough sample, or the pressure is low enough, it could sublime, converting directly from ice into steam.

This would result in a false negative if the original sample did, in fact, contain water, because spending that much time between gathering a sample and analyzing it invalidated the test results. This of course, assumes that the first paragraph is true.

The reason for sifting it is probably because anything too large could damage their 'oven.'

Re:invalidate the tests

[sveard]

Ever wonder why ice cubes shrink after they've been in a freezer for a really long time? I know. I also prefer to use deuterium ice.

Re:invalidate the tests

[Ihlosi]

Water doesn't sublime.

I have a phase diagram of water here that disagrees with you (and anyone who modded you informative. geez, people, hand in your geek licenses please).

See that boundary line in the lower-left corner, where vapor and ice are directly adjacent to each other ? That's where water sublimes.

http://encarta.msn.com/media_461541579/phase_diagram_for_water.html

Re:EZ Bake?

[rkanodia]

Sorry. Under Martian law, bakers and other wizards are forbidden!

Re:Vibrating the screen

[Harmonious Botch]

The martian critter sitting on the screen is probably tired of foreplay by now...

Too much vibration...

[Volante3192]

Great, now all Phoenix is going to say to NASA is TILT!

We're gonna have to fly someone up there to deposit a dollar in quarters into Phoenix now...

What were they thinking?

[elrous0]

Why would they have designed the thing to have such a low tolerance filter in the first place? Hell, most *terrestrial* soil wouldn't even make it into that oven. I sure wouldn't use it for a soil whose composition was largely a mystery. And, even if they get something, will it truly be representative of the Martian soil, or just the finest particles of it that finally made it through?

Re:What were they thinking?

[SBacks]

Why would they have designed the thing to have such a low tolerance filter in the first place? Cuz they had to strap it on a rocket and shoot it to Mars? I kinda doubt a full sized lab furnace would be under the weight requirement.

Re:What were they thinking?

[drrck]

We're talking about introducing material into an oven to be vaporized for Mass Spec analysis. You don't want or need to deal with huge amounts of material to tell what compounds are in the soil.

Re:What were they thinking?

[Sponge Bath]

1 mm diameter particles are tiny.

For the common man who needs a frame of reference: This is the same length as the distance between the solder balls of many BGA IC packages.

Re:What were they thinking?

[Changa_MC]

1 mm diameter particles are tiny.
For the common man who needs a frame of reference: This is the same length as the distance between the solder balls of many BGA IC packages. Good lord, that didn't help him at all. For the common man: a dime is about 1mm thick.

Re:What were they thinking?

[maxume]

The common man has long since spent his last dime.

Re:What were they thinking?

[Original Replica]

You don't want or need to deal with huge amounts of material to tell what compounds are in the soil.

You also don't want half of the contents to sublimate by leaving them exposed to sunlight and friction/heat from a vibrating screen. Considering how important it was to land where there was ice (polar landings are tough) you think they would be a bit more careful to preserve that ice since that is where they hoped to find the organic compounds.

Hooray

[Haoie]

We've come along way from the Easy-Bake Oven.

But I still bet the Phoenix can't make smores.

it's no turkey

[nguy]

To their surprise, NASA scientists discovered that, try as they might, roasting a phoenix in an oven never results in well-done meat.

Will it blend?

[kharri1073]

They should have consulted willitblend.com before they sent the craft to mars. I'm sure the people at will it blend would have had no problems getting some martian dirt through a micro screen.

I thought vibrators were for when...

[exp(pi*sqrt(163))]

...you didn't want a bun in the oven.

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[Spy der Mann]

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Oven #4 is the first oven?

[otter42]

From my reading of the FA, it seems that oven #4 is the first oven they tried. That's important, because it seems that whether the soil gets there or not, they only get one try with each oven. So they still probably have 7 more to go. Hurrah, NASA!

Re:Once again...

[Anonymous Coward]

The actual oven is only about 1 mm in diameter. The screen covers a funnel that directs a small sample of soil into the oven. What happens when you let a 2 mm particle fall on a 1 mm oven? That's right...it cover the opening and nothing else gets in.

Believe it or not, there are people at NASA and JPL capable of seeing the big picture.

In this case, the soil turned out to be clumpier than anyone expected, and before you ask, yes they did try to determine what it would be like before launch, using data from the Vikings and the rovers.

Re:investment vs result

[Ihlosi]

its depressing how feeble and unreliable the space probe design are compared to the insane amounts of investment.

And you're ... qualified to make this statement ? Are you any kind of engineer (ME or something along those lines would be best) ?

shovel, to scoop up dirt, instead of some decent drilling apparatus that could get samples from much deeper and from harder surface.

Yes, of course, a drill. How brilliant. So where do you get all the power to run that drill ? How do you keep it lubricated ? How do you keep your lubricant from polluting your samples ? How do you move the drill around to drill in different places ? And remember, this is a space probe. Weight is at a premium.

solar panels that get covered in dust because someone is too lazy to add windscreen wipers.

So how well do your windshield wipers work when its completely dry ? How do you avoid scratching the surface of the solar panels (which will permanently degrade their output) ? What do you do when the wiper breaks down in the middle of its operation (which will knock out that solar panel completely) ?Also, now we've learned that Martian winds are strong enough to keep the panels clean.

making things heavier and more robust than needed resulting in insane liftoff prices.

Hey, you're the one suggesting adding all kinds of heavy (and useless) stuff to probes.

if businesses would be contracted to design and make happen space missions we would have 1000 men moon base by now.

If business were contracted to do so, we'd have a lot of dead people on the moon, a couple of businesses that have gone belly-up, and some shareholders and CEOs that got insanely rich in the process. Not sure if that's any better than what we have now.

you could just give the budget and say use what you must to accomplish it and the leftover is your profit.

Great, give me the money, here's your space probe. Business closes, owners and CEOs make off with wads of cash, space probe fails because they've been cutting a few corners too many. And don't even think of delaying payment until the probe was successful - no businessperson in their right mind would accept such a delay in payment.