Phoenix on Mars - Page 14

01101001 · #**391** (**permalink**) 01-August-2008, 01:09 AM

Quote:

Originally Posted by timb

Sara Hammond (NASA spokeswoman) says they were "surprised" to find ice in the sample.

I was surprised there was ice in that supposedly dry sample, too.

===

Links? Here. Take two. They're free.
NASA Phoenix Mission
University of Arizona Phoenix Mars Mission
University of Arizona Phoenix Mars Mission: Lander Gallery
JPL Phoenix Mission News
NASA Phoenix Twitter Feed
NASA Phoenix Multimedia
CSA Phoenix Mars Mission
Planetary Society: Phoenix Mission
Planetary Society: Phoenix Non-SSI Raw Images
Planetary Society: Phoenix Sol-By-Sol Summary
Planetary Society: Weblog
Emily Lakdawalla Ustream video chat (Wednesdays)
Texas A&M University Phoenix SSI Raw Images Directory
Unmanned Spaceflight Forum: Phoenix 2007/8
Google Mars landing site
NASA TV (or NASA TV Yahoo! source or high-resolution)
NASA TV Media Channel

01101001 · #**392** (**permalink**) 01-August-2008, 02:32 AM

Quote:

Originally Posted by 01101001

[From the July 31 briefing Q&A] Where's MECA? 2nd wet test? Provocative? Why? Notified Presidential Science Adviser? There are uninterpreted signals. Too early to say what we have besides the salt and alkalinity we already described. Soil different than expected.

(That was a weird question. Woo-woo reporter? (Edit: Later, I saw that was Craig Covault, Aviation Week, in my experience not prone to outrageousness. I wonder what he was trying to get at.))

At UMSF, article in topic Sol 65 and after (edit: reorganized into topic The MECA story), Emily Lakdawalla answers others' questions about Craig Covault, and mentions (mild) MECA rumors she's heard:

Quote:

I've heard some very vague rumor to the effect that the MECA guys have found something interesting -- but that's all I know. [...]

Cool. Much more idle speculation and questions there.

01101001 · #**393** (**permalink**) 01-August-2008, 03:07 AM

Maybe we could use a reminder of what the MECA Wet Chemistry Lab might tell us, worthy of a presidential heads-up (or comedic reference thereto).

THE 2007 PHOENIX MARS SCOUT MECA WET CHEMISTRY LABORATORY (PDF), an abstract:

Quote:

In addition to investigating the geochemistry, the MECA-WCL directly
addresses a variety of astrobiology goals. Among these is its search for habitable zones and
biosignatures by, (1) identifying potential chemical energy sources available to support life, (2)
determining whether the subsurface geochemistry is hostile to life, and (3) identifying the
potential of the geochemical environment to preserve paleontological evidence.
[...]
The WCL for the 2007 Phoenix, and future Mars missions, provides a low mass/energy device
for obtaining unique information about the potential habitability and history of the aqueous and
geochemical environment.

Tufts University: Microscopy, Electrochemistry, and Conductivity Analyzer

Quote:

The WCL has four single-use modules consisting of a beaker assembly and an actuator assembly. The modules mix soil samples with a leaching solution in a pressure vessel, for electrochemical analysis. Each beaker assembly (Thermo Electron) is instrumented with an array of ion selective electrodes (ISE) and electrochemically-based sensors. This array of sensors allows for the determination of a wide variety of inorganic anions, cations, selected heavy metals (via ASV), and electrochemical parameters, including:

Conductivity
pH (3 sensors)
Cl- (2 sensors)
Br- (2 sensors)
I- (2 sensors)
NO3-
SO4= (using Ba ISE)
K+
Ca2+
Mg2+
NH4+
Na+
Pb/Cu/Cd/Zn/Fe (ASV)
Cyclic Voltammetry
ORP (redox potential)
Temperature
Li Reference (3 sensors)

01101001 · #**394** (**permalink**) 01-August-2008, 06:44 AM

Quote:

Originally Posted by Swift

I had not know that their thermal analysis was done with a step-wise temperature schedule (ramp up and soak).

If you haven't seen it, view the brief animation of the TEGA mechanism. I thought it was interesting the path the sample takes. It can be found at Animation of TEGA Sample Delivery and Analysis.

From NASA Phoenix Mission Multimedia

Some other animations that just appeared there, from the briefing:

How Phoenix Creates Color Images
Full-Circle Color Panorama of Phoenix Landing Site on Northern Mars, Animation
Testing of Icy-Soil Sample Delivery in Simulated Martian Conditions
Zenith Movie showing Phoenix's Lidar Beam

01101001 · #**395** (**permalink**) 01-August-2008, 08:22 AM

Sol 66 Raw Images are arriving.

The usual assortment of yawn-producing telltale and atmosphere images. 46 so far.

JonClarke · #**396** (**permalink**) 01-August-2008, 08:51 AM

I am very intrigued by the non release of the 2nd MECA wet chemistry results!

On the ice melting temperature, the fact that it melted at zero degrees shows that the water was very pure. This confirms the first wet cell run that showed that soil salinity was no more than 1000 ppm TDS.

Jon

Warren Platts · #**397** (**permalink**) 01-August-2008, 11:40 AM

So what does the low salinity imply for the "history of water"? Probably that there wasn't much history, as in long lasting oceans?

JonClarke · #**398** (**permalink**) 01-August-2008, 01:17 PM

Interesting question Warren. Fresh water means that it is not a buried ocean, or a long lasting closed lake.

But maybe buried snow, glacial ice, or an open lake that froze over and got buried. Or infiltrating snow melt?

When you freeze water you tend to exclude salts. So the ice will tend to be low salinity anyway. But the fact that there are so few salts in the soils suggests that the water was not salty to begin with.

All good evidence that Mars is very diverse and that global cliches like "Mars is very salty" are inadequate.

Low salinity ice in a low salinity host is good news for those interested in resources that might support human settlements.

Jon

01101001 · #**399** (**permalink**) 01-August-2008, 04:16 PM

Quote:

Originally Posted by JonClarke

I am very intrigued by the non release of the 2nd MECA wet chemistry results!

Here's what Aviation Week's Frank Morring reported a few days ago, July 28, Aerospace Daily: Phoenix Soil Sample Tantalizing:

Quote:

Mars Phoenix scientists are carefully analyzing some tantalizing results from the second wet-chemistry experiment with a soil sample scooped from the Martian tundra at the beginning of July.

The testing has taken longer than expected, and may lead to more tests before the Phoenix science team is ready to announce results. An announcement of the findings could come as early as mid-August, NASA says.
[...]

The same was published a few days earlier, July 25, Aviation Week: Scientists Excited Over Phoenix Soil Sample

01101001 · #**400** (**permalink**) 01-August-2008, 09:06 PM

Here we go... Aviation Week's Craig Covault was asking about Presidential Science Advisers and if they had been notified of MECA results at the recent briefing. And writes:

Aviation Week: White House Briefed On Potential For Mars Life

Quote:

The White House has been alerted by NASA about plans to make an announcement soon on major new Phoenix lander discoveries concerning the "potential for life" on Mars, scientists tell Aviation Week & Space Technology.

Sources say the new data do not indicate the discovery of existing or past life on Mars. Rather the data relate to habitability--the "potential" for Mars to support life--at the Phoenix arctic landing site, sources say.

The data are much more complex than results related NASA's July 31 announcement that Phoenix has confirmed the presence of water ice at the site.

I'm not sure what's new about the second sample. We did the asparagus-patch potential after the first sample.

OK. The article compares first and second sample:

Quote:

The MECA instrument, in its first of four wet chemistry runs a month ago, found soil chemistry that is "Earth-like" and capable of supporting life, researchers said then.

It is intriguing that MECA could have found anything more positive than that, but NASA and the University of Arizona are taking steps to prevent word from leaking out on the nature of the discovery made during MECA's second soil test, in which water from Earth was automatically stirred with Martian soil.

Interesting. What could it be? What could the second sample yield that the first didn't, that would make it more habitable? Asparagus ain't chopped liver. (You can quote me on that.)

01101001 · #**401** (**permalink**) 01-August-2008, 09:38 PM

Quote:

Originally Posted by 01101001

At UMSF, article in topic Sol 65 and after (edit: reorganized into topic The MECA story), Emily Lakdawalla answers others' questions about Craig Covault [...]

And I just fed that topic a link to Covault's Aviation Week story. Maybe those fine people will have good commentary on what it might be about.

01101001 · #**402** (**permalink**) 01-August-2008, 09:57 PM

For a refresher, here's what was in the June 26 press briefing regarding the first MECA sample (and its effect on asparagus):

Quote:

Samuel Kounaves:
Uh, yes. We've had a very, very exciting day yesterday. We've, uh -- we've completed about 80 percent of the analysis on the first cell. Uh, this has been -- this is the first wet chemical analysis on the Martian soil and any other planet besides Earth by our robotic lab assistant. Uh, it's been difficult and slow, but it performed flawlessly yesterday t -- uh, and we were all very flabbergasted at the data we got back.

Uh, this is very preliminary data. But, uh, we took in -- I presume we've taken in about a-a cubic centimeter of a soil sample. And, uh, we don't know the density yet and everything. But we-we appear to have gotten what we were looking to get. Uh, in general, we, uh, appear to have a variety of soluble species of ionic species of minerals or nutrients, whatever you want to call them.

Uh, our biggest, uh -- it wasn't a surprise, I guess. We-we knew there was some level of acidity or alkalinity on Mars. But the first data indicates that the, uh, soil that we've sampled on the surface about an inch from the -- from the -- uh, an in -- the top inch of the surface material has a pH that would be in the alkaline re-region, somewhere probably between eight or -- pH of eight or nine.

So it's a very alkaline soil, uh, where we've, uh, analyzed it. Uh, we've also seen levels, significant levels of a -- of several other ionic species, soluble ionic species, uh, including, uh, magnesium, sodium, potassium, uh, uh, chloride. Uh, and we still have-have not done the analysis for sulfate. That's coming up in the next couple of days.

Uh, there are some other species there probably. We have a lot of lab work to do and other ways to interpret this data. There are some hidden species in this, uh, set, uh, that we're still working on. Uh, we basically have found, uh, what appears to be the requirements, the nutrients to support life, whether past, present or f-future.

Uh, the sort of soil you have there is the type of soil you'd, uh, probably have in your backyard, v -- you know, alkaline. You might be able to grow asparagus in it really well. [laughter] But strawberries, probably not very well. Uh, and again, this is, uh, one more piece of evidence showing that, uh, these salts got there by some sort of, uh, liquid water action at some point in the history of Mars.

Uh, and so -- and-and it's also surprising. This is very similar to the sort of, uh, analyses or analytical results we got from Antarctica dry valleys when we were down there, uh, very similar soils, very similar analyses. So all in all, it's, uh, very exciting for us. And, uh, we still have -- I know there -- have another part of the experiment to do and, uh, three more cells to go. And, uh, hopefully, we'll see even more. And, we'll have more results later.

And the less uh-ful June 26 news release:

Quote:

"This soil appears to be a close analog to surface soils found in the upper dry valleys in Antarctica," Kouvanes said. "The alkalinity of the soil at this location is definitely striking. At this specific location, one-inch into the surface layer, the soil is very basic, with a pH of between eight and nine. We also found a variety of components of salts that we haven't had time to analyze and identify yet, but that include magnesium, sodium, potassium and chloride."

"This is more evidence for water because salts are there. We also found a reasonable number of nutrients, or chemicals needed by life as we know it," Kounaves said. "Over time, I've come to the conclusion that the amazing thing about Mars is not that it's an alien world, but that in many aspects, like mineralogy, it's very much like Earth."

fredquimbo456 · #**403** (**permalink**) 01-August-2008, 10:22 PM

It appears something interesting happened when they mixed water from earth with martian soil during the second wet test:

Quote:

The key is in the soil and water, and how the two behave together at that site on Mars, not the expected confirmation of water ice at this stage in the mission, Mars investigators told Aviation Week.

Sounds fascinating. Now what are the possibilities here?

Quote:

The Microbial Detection Array will mix water and sterilized soil (the nutrient) with unsterilized Mars soil, and look for any signs of metabolic activity.

Can we assume they have indeed found signs of microbial metabolic activity, even growth?

More on the MDA:

Quote:

MDA is designed as a test bed for an astrobiology field instrument to detect microbial metabolic activity in terrestrial or extraterrestrial geological soil samples. MDA employs electrochemical sensors in a unique differential chamber configuration, able to detect minute changes in the chemical composition between the two otherwise identical chambers. Both chambers are filled with identical autoclave-sterilized, sample-water mixtures. Only one of the chambers receives an additional minute, non-sterilized inoculation sample. Under the minimal assumptions that the geological sample contained nutrients (energy), organisms, and required water to initiate growth, the differential electrochemical measurements would now allow detection of metabolic activity, in addition to the electrochemical characterization of the soil samples in both chambers.

More:

Quote:

Replication of the experiment and positive results would lead to the conclusion of biologically induced changes. Changes resulting from non-biological chemical reactions of whatever type are canceled out by the control. The replication of the procedure, split sample, and minimal inoculation protocol, eliminate non-biogenic causation. ... This life detection system makes minimal assumptions about the nature of any life on Mars. It assumes only that, after addition of water, the microorganism replicates and that in the process will produce small changes in its immediate surroundings by consuming, metabolizing, and excreting a number of molecules and/or ionic species.

01101001 · #**404** (**permalink**) 01-August-2008, 10:36 PM

Quote:

Originally Posted by fredquimbo456

More on the MDA:

The MDA (Tufts University: Microbial Detection Array (MDA), a Novel Instrument for Unambiguous Detection of Microbial Metabolic Activity in Astrobiology Applications (PDF)) is a prototype still on Earth, right? I doubt it has detected any Mars microbes.

Quote:

Originally Posted by fredquimbo456

Can we assume they have indeed found signs of microbial metabolic activity, even growth?

Certainly not with cause. None of the hints warrant that sort of assumption.

fredquimbo456 · #**405** (**permalink**) 01-August-2008, 11:31 PM

You're right. So, no growing microbes yet. But we can try and narrow down the possible discovery if we look at the WCL sensor array, right?

Kounaves said after the first test:

Quote:

If you dig down 30 centimeters, to the ice table, you can find that the ice-soil interface somehow acts to concentrate a lot of the chemicals that MECA is searching for.

Are we talking about such a sample here?

JonClarke · #**406** (**permalink**) 02-August-2008, 12:35 AM

Quote:

Originally Posted by fredquimbo456

It appears something interesting happened when they mixed water from earth with martian soil during the second wet test...

The Viking soils showed peculiar activity when water was added. Perhaps similar behaviour here?

Jon

JonClarke · #**407** (**permalink**) 02-August-2008, 12:47 AM

Quote:

Originally Posted by 01101001

Here's what Aviation Week's Frank Morring reported a few days ago, July 28, Aerospace Daily: Phoenix Soil Sample Tantalizing:

The same was published a few days earlier, July 25, Aviation Week: Scientists Excited Over Phoenix Soil Sample

Speculations on my part:

1 Very high levels of ammonium and/or nitrate (both usually indicators of biological activity on Earth)

2 Very strongly reduced soils (ditto)

3 Very acidic soils (unexpected so close to very alkaline soils)

4 Hypersaline soils (unexpeted so close to low salinity soils and fresh water ice)

5 Unusual changes in chemistry over experiment time (eg. pH, eH, salinity, temperature) indicating unexpected chemical activity.

Because of their significance, 1 and 2 would need verification to prevent misinterpretation and mis-use of the data.

Jon

01101001 · #**408** (**permalink**) 02-August-2008, 01:30 AM

Quote:

Originally Posted by JonClarke

Speculations on my part:

1 Very high levels of ammonium and/or nitrate (both usually indicators of biological activity on Earth)

2 Very strongly reduced soils (ditto)

But, what of the hint in the article, if the sources were straight:

Quote:

Sources say the new data do not indicate the discovery of existing or past life on Mars. Rather the data relate to habitability--the "potential" for Mars to support life--at the Phoenix arctic landing site, sources say.

Does that fit?

I was also thinking about the possibility of an acidic sample, in contrast to the first, just indicating variety of habitability. (Here: aspargus; over there: OK, strawberries!)

The bit about the key being a water/soil behavior thing, though... I'm still wondering how the second sample would differ from the first in this regard. The soils both behaved with similar Earth water. What sort of "behavior" could indicate more habitability -- but not existing life -- than they already saw?

Where are our chemists on this?

Procyan · #**409** (**permalink**) 02-August-2008, 02:12 AM

Welp there is one aspect to this alkaline pH that is most tantalizing relative to the Phoenix mission to elucidate Martian natural history. Its about the rather extreme difference, a kind of "geochemical divide" (love it, love it) between the sulfate rich, acidic regions like Meridani and what seemed to be more ancient, reducing environments. I have to wonder if they've got a chemical reaction that quickly released CO2. If so I would speculate that they saw the pH go rapidly from alkaline to acidic. Glycolysis (fermentation) on earth decreases pH (by releasing acid). Once carbonates are acidified they become airborne as CO2 gas. This all links in with theory's related to the Squyre's team discovery of acid sulfates. I asked Prof. Andrew Knoll of Harvard U for his thoughts on this and he wrote back!

I don't think Prof. Knoll will mind me reprinting his letter below:

At 10:24 PM 1/3/2006, you wrote:
>Dear Prof. Knoll,
>
>I've been reading the latest from your group and others on Martian
>chemistry. Could you comment on what seems an interesting point to me?
>the allan hills sample contained carbonates that may or may not have
>been biological. Either way, the evidence from the rovers suggests that
>the soils are acidic and the interesting "water-table" idea floated by
>S. Squyres would give everything a periodic dip in highly oxidizing
>fluids.
>
>Hope I haven't overlooked something and without wishing to overdraw on
>the available bank of data... can these opposing chemistries be
>harmonized? Could ALH ### predate a more modern "acid era"? Has Mars
>really lost almost all of its carbon to space?
>
>I would close with a promise not to engage you in endless dialog if you
>answer.
>
>Best wishes, we are enjoying the show very much indeed!
>ProCyan

>Dear ProCyan,

Your question is a good one. We know that carbonates will not
precipitate from strongly acidic solutions that deposit jarosite; thus, the
fluids that percolated through the parent rocks of martian meteorites could
not have been strongly acidic like those at Meridiani. Similarly, nearly
all the iron in the Meridiani outcrops rocks has been oxidized, whereas
iron in sulfides and carbonates in martian meteorites is reduced. Thus,
the "meteoritic" and Meridiani environments differed in both pH and Eh. On
the present day Earth, we find variations in pH (uncommonly, highly acidic
waters develop locally, many of which deposit jarosite, but not
carbonates), and redox variations are common -- just dig into the mud of a
salt marsh, where pyrite is forming a few millimeters below an oxygen rich
atmosphere. So the simple answer is that the two deposits reflect
different environments. Whether these reflects environmental heterogeneity
at any one point in time or globally homogeneous environments that evolved
through time remains unknown -- my guess is that both occurred.

You might check out a recent paper in Science magazine by Bibring
et al. (the exciting Mars Express orbital program), which documents clay
minerals in martian southern highlands. Interestingly, both experimental
and observational data show that under acidic conditions, silicate minerals
in basaltic volcanic rocks will simply dissolve, whereas under less
strongly acidic conditions, basalt minerals will fractionate to form
clays. Controversially (but I'm rooting for it), Bibring et al. suggest
that early martian environments were less acidic, forming clays, whereas
after about 4.0 billion years ago, acid environments took over, producing
sulfate rich surface rocks.

My MER colleague Scott McLennan has a manuscript in the works that
specifically discusses the "geochemical diviide" that differentiates
Meridiani deposits from those of Mars meteorites. You might ask Scott
about his views.

Hope these comments help,

Andy Knoll

ProCyan: There is a story to tell and these guys are nutting it out step by step. Phoenix cannot directly measure living processes, but life always finds a way to tell its story. Now will someone please tell me how we're supposed to wait until MID AUGUST for "the rest of the story"?

Olowkow · #**410** (**permalink**) 02-August-2008, 04:43 AM

Pretty new here, and I tried to read most of the thread, so I'm not sure how off topic this is. I just have so many questions and the info on the web seems to be pretty sparse. Now that we know that it is in fact ice, it seems odd to me that water ice could exist just below the surface for, one has to assume, billions of years without subliming, since the small samples exposed to the atmosphere disappeared in just days. Anyone else find this remarkable? Could the soil be that air tight? Is anyone speculating on how it could have gotten there, and get covered quickly enough to prevent sublimation?

01101001 · #**411** (**permalink**) 02-August-2008, 06:10 AM

Welcome to the BAUT Forum.

Quote:

Originally Posted by Olowkow

Now that we know that it is in fact ice, it seems odd to me that water ice could exist just below the surface for, one has to assume, billions of years without subliming, since the small samples exposed to the atmosphere disappeared in just days.

I think it's Winter. Happens every martian year. It gets really cold there. Cold enough for water and carbon-dioxide ice to form. Almost all the CO2 probably does sublime away in Spring, but the soil shades and insulates the water ice enough that some remains until the cold returns.

And, notice that the exposed large chunk of ice, named Snow Queen, under Phoenix, is even exposed and just its low surface area to volume helps it persist. It was only the small chips with high surface area to volume ratios that vanished.

(And, don't assume things are so very stable for billions of years. Expect the climate to change some with Mars' obliquity changes. When the north polar region becomes pointed at the sun, it likely gets quite warm for that half of the year.)

RBG · #**412** (**permalink**) 02-August-2008, 07:29 AM

One thing I picked up on that might need some reconciliation or explanation:

Above we read quotes about all the salts that were discovered in the soil sample. But the recent oven sample showed the ice changing to water apparently at 0 degrees suggesting a pure H20 without any salt content.

Perhaps salty soil and pure ice can coexist? That doesn't seem right.

RBG

JonClarke · #**413** (**permalink**) 02-August-2008, 08:25 AM

Quote:

Originally Posted by RBG

One thing I picked up on that might need some reconciliation or explanation:

Above we read quotes about all the salts that were discovered in the soil sample. But the recent oven sample showed the ice changing to water apparently at 0 degrees suggesting a pure H20 without any salt content.

Perhaps salty soil and pure ice can coexist? That doesn't seem right.

RBG

The first MECA wet chemistry cell indicated that total salts were no more than 1000 ppm. That is not very salty at all.

Jon

slang · #**414** (**permalink**) 02-August-2008, 09:54 AM

Quote:

Originally Posted by RBG

Above we read quotes about all the salts that were discovered in the soil sample. But the recent oven sample showed the ice changing to water apparently at 0 degrees suggesting a pure H20 without any salt content.

Was it at exactly 0 C or just close enough to it? I don't remember seeing error bars with the results (and I wouldn't expect that in press releases).

01101001 · #**415** (**permalink**) 02-August-2008, 01:52 PM

Sol 67 Raw Images began arriving about 4 hours ago. Right now it's 23 images of telltale and atmosphere. Nothing provocative. Don't wake the science advisor.

JonClarke · #**416** (**permalink**) 02-August-2008, 01:58 PM

Quote:

Originally Posted by slang

Was it at exactly 0 C or just close enough to it? I don't remember seeing error bars with the results (and I wouldn't expect that in press releases).

Ice melting temperature is a very sensitive indicator of salt content, as I recall, which is why it is used to determine salinity in fluid inclusions.

Jon

01101001 · #**417** (**permalink**) 02-August-2008, 02:12 PM

Quote:

Originally Posted by slang

Was it at exactly 0 C or just close enough to it? I don't remember seeing error bars with the results (and I wouldn't expect that in press releases).

I think just close enough to call it 0C to the press. That was my recollection of Bill Boyton's first answer in Q&A for the press briefing.

ScienceNews, or their source, got similar, Officially Ice:

Quote:

When the oven heated the soil, some of the sample melted at 0° Celsius, the melting point of ice, and the TEGA also detected water vapor during the analysis, Boynton noted.

It probably wasn't at 1 atmosphere when it melted though, having come from Mars ambient, and its being warmed through to room temperature in a sealed oven, I can't even guess if the pressure would be below or above 1 atmosphere when it changed phase.

I think the 0C quote is just a round number for mass consumption, but it must come as a blow to those who advocated a briny Mars, with soil that might be muddy at typical daytime temperatures.

RGClark · #**418** (**permalink**) 02-August-2008, 03:29 PM

On freezing, most of the salt is forced out of the ice matrix, so that the water ice can still be pure H2O even with salts present in the sample.

Bob Clark

nutant gene 71 · #**419** (**permalink**) 02-August-2008, 03:55 PM

Quote:

Originally Posted by slang

Was it at exactly 0 C or just close enough to it? I don't remember seeing error bars with the results (and I wouldn't expect that in press releases).

I'm rusty in my chemistry, but doesn't the atmospheric pressure affect the boiling temperature of water? Here's Wiki on Boiling point:

Quote:

A liquid in a vacuum environment has a lower boiling point than when the liquid is at atmospheric pressure. A liquid in a high pressure environment has a higher boiling point than when the liquid is at atmospheric pressure. In other words, the boiling point of liquids varies with and depends upon the surrounding environmental pressure.

So if Martian atmosphere is some 10% pressure of Earth's, pure H2O would boil lower than 0 C. Is that puzzling? Or that there must be some salt in the ice, since that would elevate the boiling point to where it boiled at 0 C?

Puzzling to me.

01101001 · #**420** (**permalink**) 02-August-2008, 04:13 PM

Quote:

Originally Posted by nutant gene 71

So if Martian atmosphere is some 10% pressure of Earth's, pure H2O would boil lower than 0 C. Is that puzzling?

No. Again, the ice wasn't melting in Mars atmosphere. It was inside a sealed oven, and before it melted it probably sublimed some in the increasing warmth, as well as other volatile matter, if present, like CO2, turning gaseous. Inside that sealed compartment, the pressure was unlikely to be as low as Mars ambient.

(And, Mars air pressure is about 1% of Earth's 1 atmosphere.)

NASA Phoenix Mission Multimedia: June 20 Briefing Transcript:

Quote:

Peter Smith:
Hi, Miles. This is Peter. Uh, the, uh, plan for-for sampling the ice is to gather it up rather quickly using our power tool we call the rasp. Uh, to deliver it within 30 minutes to the TEGA instrument. And then, as it is verified that it's gotten into the oven, the oven is sealed. And once it's sealed, it's no longer able to sublimate into the atmosphere.

It has a-an airtight seal on it pretty much. So it's-it's really that -- the hurry is to get it from the surface, once we've collected it and verified it's collected, into the instrument and seal that instrument within 30 minutes.

Miles O'Brien:
Okay. And does it pass through a liquid stage inside that oven once it's sealed up?

Peter Smith:
Only if the oven goes above, uh -- yes, actually, it probably does go through a liquid stage. As we heat the oven up above zero, uh, it will liquefy because the pressure is high enough. But remember, the boiling point of water on Mars at-at this pressure is four degrees Centigrade. So there's only a few degrees in which that-that material can go from ice to liquid and then to gas.

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