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Unmanned Spaceflight.com _ MSL _ MSL - SAM and CHEMIN

Posted by: Astro0 Nov 21 2012, 11:46 AM

ADMIN NOTE: Hi All, a new topic for the discussion of the science from the SAM and Chemin instruments.
There has been a very important http://www.unmannedspaceflight.com/index.php?showtopic=7514&view=findpost&p=194625.
Please remember
http://www.unmannedspaceflight.com/index.php?act=boardrules at all times when discussing matters in this section.

Posted by: pospa Nov 21 2012, 05:24 PM

MSL Status Report 11.20.2012:
"... Although Curiosity has departed the Rocknest patch of windblown sand and dust where it scooped up soil samples in recent weeks, the sample-handling mechanism on the rover's arm is still holding some soil from the fifth and final scoop collected at Rocknest. The rover is carrying this sample so it can be available for analysis by instruments within the rover if scientists choose that option in coming days."

If the latest SAM analysis result IS "one for the history books" then I would expect repeated measurement of the same sample.
Is there any indication of such a plan for upcoming days (in addition to first drilling)?



Posted by: Fran Ontanaya Nov 21 2012, 06:45 PM

Something for reference: http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=786403

Posted by: Don1 Nov 22 2012, 06:23 AM

SAM is of course capable of detecting gases evolved from heated samples, and measuring the isotope ratios. Such gases would be expected to include CO2 and water, and possibly HCl or Cl2.

Posted by: nprev Nov 22 2012, 06:34 PM

Mod note: Two posts discussing rule 1.3 changes moved http://www.unmannedspaceflight.com/index.php?showtopic=7514&pid=194689&st=0&#entry194689.

Posted by: RonJones Nov 22 2012, 07:35 PM

I have not seen any specific statements from the Curiosity science team regarding the ability of SAM to detect organics if perclorates are present in a soil/rock sample. Since SAM first heats the sample up to a high termperature (e.g., 1000 deg.) to vapaorize the sample, would this not destroy organics if perclorates are also present in that sample? Since we have known about the potential for perclorates in the Martian soil since the Pheonix results reported in 2008, I asume this has been considered in some detail by the Curiosity team. Anyone have any information on what level of perclorates would be sufficient to cause significant problems for SAM being able to detect organics (I assume that would also depend on the level of organics in the sample)?

Posted by: mcaplinger Nov 22 2012, 07:43 PM

QUOTE (RonJones @ Nov 22 2012, 12:35 PM) *
I have not seen any specific statements from the Curiosity science team regarding the ability of SAM to detect organics if perclorates are present in a soil/rock sample.

Have you read http://link.springer.com/article/10.1007/s11214-012-9879-z ?
QUOTE
The presence of perchlorates and other oxidants, if present in the martian soil and
rocks at Gale crater, could have implications for the SAM search for organics as some of
these compounds could be transformed to CO2 in the oven. If perchlorates are present, a small amount of the organics may form chlorohydrocarbons that could be detected by the SAM GCMS experiment. The presence of perchlorates
may also be indicated by O2 , HCl, or Cl2 evolution in a SAM EGA experiment or these
compounds may be detected by the ChemCam instrument. Similarly,
the presence of high concentration H2 O2 in sediments could manifest itself in the form of
formaldehyde or methanol, species that are potentially detectable by SAM.


Posted by: nprev Nov 22 2012, 07:44 PM

One fascinating finding would be if perchlorates are not present in these first samples.

I rather suspect that there is considerable diversity in the composition of martian soil at the regional scale once you get beneath the ubiquitous wind-deposited global dust layer. Recall the serendipitous exposure of subsurface chemical deposits at Gusev by Spirit from the dragging wheel.

Posted by: Burmese Nov 22 2012, 08:55 PM

No data yet to work with until they present their findings in Dec, however the news so far out of JPL is illustrative:

I think this announcement will be of relatively mild significance here, the fact that the scientists are even dropping hints at this stage is an indication that is the case. There have been elements and compounds that we are pretty certain are there on Mars and these are simply the 1st instruments capable of definitive proof. It is a feather in Curiosity's hat(hopefully the 1st of many), but just that, not a turkey on the table. That they plan to present the data at a science forum, and not at the typical news conference is simply intelligent planning. The audience will be of a caliber to hear the word 'organic' and understand the nuances inherent in that whereas, if they 1st say that word at a news conference full of reporters, that would be tantamount to yelling 'fire' in a theater and likely induce spontaneous combustion in the room.

If they ever encounter anything more significant, we won't hear word one coming from JPL for a long time, as the watchword would undoubtedly be one of Carl Sagans' better known pronouncements: "Extraordinary claims require extraordinary proof"

Posted by: nprev Nov 22 2012, 09:11 PM

Very good comment, Burmese; thank you!

In general, findings of scientific significance tend to be deeply underwhelming to the general public. Strongly advise our members not to be swayed by the usual mass media sensationalism; they are, after all, trying to sell a product and therefore marketing takes precedence over accuracy and critical thinking.

We will find out what it is in due course. In the meantime...the journey continues!!! And it's barely begun. wink.gif

EDIT: Also, a word about organics.

It is overwhelmingly likely that at some point organic molecules will be detected by Curiosity. However, it is also overwhelmingly likely that most if not all of same came from carbonaceous meteorites, and we have seen both direct evidence of recent impacts on Mars from the orbiters as well as iron-nickel meteorites from the MERs. Bear in mind that compounds up to and including amino acids have been found in terrestrial meteorites; therefore, it is reasonable to expect the same sorts of findings from Curiosity as, over time, these objects have weathered and become incorporated into the martian soil.

Bottom line is that ANY discovery of organics means just that: Discovery of organics. Nothing less...and nothing more.

Posted by: RonJones Nov 23 2012, 01:56 AM

I suspect that if any new finding by MSL would be of significant interest to the general public it would be announced at a NASA press conference rather than just with paper to a science conference. The findings expected to be disclosed in a couple of weeks may be very interesting to planetary scientists, but may be not be of such a nature to be understood or appreciated by the general public. Let's wait and see if NASA schedules a press conference before the start of the conference.

Posted by: Astro0 Nov 23 2012, 02:30 AM

ADMIN NOTE: Can I remind everyone that this thread is for "Discussion of the science/results from these instruments" and not for debating why, how or when information will be/should be released, etc. This thread was opened with some very specific rules put in place and if it goes off-topic, will result in its closure and Rule 1.3 changed again. This was an attempt by the Admin Team to allow for discussion on a topic that has been 'out of bounds' in the past. It's up to members to make it work - if it doesn't then it's off the agenda forever.

Posted by: marsophile Nov 23 2012, 03:54 AM

QUOTE (RonJones @ Nov 22 2012, 12:35 PM) *
...would this not destroy organics if perclorates are also present in that sample?


All you have to do is wash the sample in water before pyrolyzing it. That would remove water-soluble components like perchlorate while retaining hydrophobic organic substances if any are present. I was under the impression that Curiosity has this capability or something like it.

Posted by: mcaplinger Nov 23 2012, 06:49 AM

QUOTE (marsophile @ Nov 22 2012, 08:54 PM) *
All you have to do is wash the sample in water before pyrolyzing it...I was under the impression that Curiosity has this capability or something like it.

Not that I'm aware of. SAM has its wet chemistry cells but the SAM instrument paper referenced above doesn't indicate that this is their purpose -- see section 4.6, "Solid Sample Measurements Based on Wet Chemical Processing".

Note that Springer-Verlag has made all of the MSL instrument papers free-access until the end of the year, so there's no excuse not to read up if you're interested -- http://link.springer.com/journal/11214/170/1/page/1

Posted by: MrNatural Nov 23 2012, 03:08 PM


Can we discuss SAM's stereochemistry capabilities? I believe that SAM can sort out chirality, but I have seen very little written about this. As we all know, stereochemistry would allow us to help us determine, ah I hesitate to say this, the genesis of some organics. As far as I can tell, SAM can determine if a peak is chiral, but I am not sure if it can tell if there is a preponderance of L- versus D- for a particular organic chemical.

Posted by: mcaplinger Nov 23 2012, 04:09 PM

QUOTE (MrNatural @ Nov 23 2012, 08:08 AM) *
Can we discuss SAM's stereochemistry capabilities? I believe that SAM can sort out chirality, but I have seen very little written about this.

First, ask in the SAM/Chemin thread. Second, read the SAM instrument paper. Third, do a simple google search for "sam msl chirality" and then you will be prepared enough to ask questions.

Posted by: elakdawalla Nov 23 2012, 05:18 PM

Actually they're only free through Nov 30 -- one more week. Get 'em while they're hot.

Posted by: marsophile Nov 23 2012, 07:24 PM

QUOTE (marsophile @ Nov 22 2012, 08:54 PM) *
... or something like it.


Thanks very much for those links, especially this one:

http://link.springer.com/article/10.1007/s11214-012-9879-z/fulltext.html

This image from the above link illustrates what I was trying to recall:



There are chemical solvents that can separate possible organics from the sample before heating, and also there is initial heating at a lower temperature.

Posted by: Don1 Nov 24 2012, 04:49 AM

SAM has a number of different modes of operation. The most common mode is going to be evolved gas analysis. On heating minerals like carbonates, sulfates and perchlorates will decompose, yielding gases like CO2, SO2, Cl2 and HCl. Water trapped in the crystal structure of minerals will also be driven off. SAM has a lot of capability to measure the isotope ratios for CO2 and H2O. If those isotope ratios differ from those of gases in the present Martian atmosphere, that will be an interesting result. The isotope ratios of Martian atmospheric gases have changed over time due to the loss of atmosphere to space. The isotope ratios of carbon and oxygen in carbonate minerals would be the same as that of the atmosphere at the time of their formation.

What about organics? If both organics and perchlorate are present in the soil SAM would see chlorohydrocarbons. If the soil at this site is different from the rest of Mars, then organics might be present without perchlorate. In that case SAM would detect the breakdown products of the organics. Detection of organics would certainly qualify as earthshattering, but the Martian surface is known to be a hostile environment for them.

If organics are suspected, I would expect a second run of SAM, this time in the wet chemistry or derivatization mode. Only 9 of the 74 sample cups contain the wet chemistry reagent. This reagent can remove perchlorates, which enables the organics in the sample to be directly detected.

Given the speed at which things move on SAM, they probably haven't gotten around to doing wet chemistry yet. If they are in a hurry to do a second run on the same sample, that would point to organics.

Posted by: Spin0 Nov 26 2012, 10:28 AM

From AGU's http://agu-fm12.abstractcentral.com/planner.jsp:
MONDAY, DECEMBER 03, 2012

Session: U13A
Results From Mars Science Laboratory Mission Four Months After Landing
1:40 PM - 3:40 PM

U13A-01. The Mars Science Laboratory Mission: Early Results from Gale Crater Landing Site (Invited)
John P. Grotzinger; Dave Blake; Joy A. Crisp; Kenneth S. Edgett; Ralf Gellert; Javier Gomez-Elvira; Donald M. Hassler; Paul R. Mahaffy; Michael C. Malin; Michael A. Meyer; Igor Mitrofanov; Ashwin R. Vasavada; Roger C. Wiens

U13A-02. Overview of the Atmosphere and Environment within Gale Crater on Mars (Invited)
Ashwin R. Vasavada; John P. Grotzinger; Joy A. Crisp; Javier Gomez-Elvira; Paul R. Mahaffy; Christopher R. Webster

U13A-03. First results from the CheMin, DAN and SAM instruments on Mars Science Laboratory (Invited)
David F. Blake; Paul R. Mahaffy; Igor Mitrofanov

U13A-04. The Radiation Environment on the Martian Surface and during MSL’s Cruise to Mars (Invited)
Donald M. Hassler; Cary Zeitlin; R F. Wimmer-Schweingruber

U13A-05. Chemical Composition of Rocks and Soils at Gale Crater, Mars (Invited)
Roger C. Wiens; Ralf Gellert; Sylvestre Maurice


Unfortunately the session is not on http://fallmeeting.agu.org/2012/scientific-program/video-on-demand-lectures-and-sessions/ list. huh.gif

Posted by: elakdawalla Nov 26 2012, 05:43 PM

Provided there's wi-fi or cellular signal, I'll be live-tweeting it!

Posted by: vjkane Nov 26 2012, 06:54 PM

QUOTE (elakdawalla @ Nov 26 2012, 09:43 AM) *
Provided there's wi-fi or cellular signal, I'll be live-tweeting it!

Thank you for being there, Emily! This is the first year in several I won't make AGU (conflicting conference), and I already have anticipatory withdrawal symptoms.

Posted by: Holder of the Two Leashes Nov 26 2012, 07:08 PM

QUOTE (Don1 @ Nov 23 2012, 10:49 PM) *
On heating minerals like ... perchlorates will decompose, yielding gases like ... Cl2 and HCl.


You sure about this? I was under the impression that mineral perchlorates (calcium and magnesium) would normally decompose by heating into the chloride salt and oxygen. There might be some HCl from the calcium perchlorate if it is the tetrahydrate, but I wouldn't expect to see Cl2 at all. Maybe I'm wrong.

Update: Right about the O2, wrong about the Cl2. See discussion below. The reaction Mg(ClO4)2 -> MgCl2 + 4O2 does occur as part of the mix, and occurs at a higher rate under earth atmospheric pressure as opposed to a vacuum. The other decomposition reaction branch (which produces chlorine) is 2Mg(ClO4)2 -> 2MgO + 2Cl2 + 7O2.

Posted by: serpens Nov 27 2012, 04:40 AM

I would suspect that the end products (and intermediate stage products) would depend on the makeup of the total sample and associated hydration states. For say pure Mg perchlorate the end product would (I think) be MgO, Cl2 and O2. If Ca perchlorate is present and depending on hydration state then HCl should be a stage product which would react to give CaCL2 and CO2. But I stand to be corrected.

Posted by: Don1 Nov 27 2012, 05:50 AM

QUOTE (Holder of the Two Leashes @ Nov 26 2012, 11:08 AM) *
You sure about this? I was under the impression that mineral perchlorates (calcium and magnesium) would normally decompose by heating into the chloride salt and oxygen. There might be some HCl from the calcium perchlorate if it is the tetrahydrate, but I wouldn't expect to see Cl2 at all. Maybe I'm wrong.



I'm not sure about the Cl2. Sounds like you know more about this than I do!

Posted by: mcaplinger Nov 27 2012, 06:21 AM

http://www.lpi.usra.edu/meetings/lpsc2012/pdf/2008.pdf and various other abstracts coming up with a google search for "sam msl perchlorate" may be of interest.

QUOTE
The parent salts of the perchlorate on Mars are unknown, but geochemical models using WCL data support the possible dominance of Mg-perchlorate salts. Mg(ClO4)2•6H2O is the stable phase at ambient martian conditions, and breaks down at lower temperatures than carbonates giving off Cl2 and HCl gas. Devlin and Herley report two exotherms at 410-478°C and 473-533°C which correspond to the decomposition of Mg(ClO4)2. They support a two-stage process:
(1) 2Mg(ClO4)2 = [MgO•Mg(ClO4)2] + Cl2 + 3.5O2
(2) [MgO•Mg(ClO4)2] = 2MgO + Cl2 + 3.5O2
If the chlorine gas produced reacts with moisture in the system or if the magnesium perchlorate has not fully dehydrated, then HCl gas can form and react with a carbonate phase to evolve CO2:
(3) CaCO3 + 2HCl = CaCl2 + CO2 + H2O

Posted by: belleraphon1 Nov 27 2012, 01:01 PM

AGU Press Conference Schedule:
http://fallmeeting.agu.org/2012/important-...edia-advisory-4

There is a Curiosity briefing (the first one) December 3 at 9:00 am PT.
Mars Rover Curiosity's Investigations in Gale Crater
Monday, 3 December 9:00 a.m.

NASA's newest Mars rover, Curiosity, has been investigating past and modern environmental conditions in Mars' equatorial Gale Crater since August. This briefing will offer findings from examining the composition and textures of targets touched by the rover's robotic arm. Curiosity is the car-size rover of NASA's Mars Science Laboratory mission. At the time of the AGU Fall Meeting, it will be four months into a two-year prime mission.
Watch live here: I don't you need to be registered???
http://live.projectionnet.com/agupress/fm2012.aspx

Edited to remove copy/paste formatting.
ADMIN NOTE: All, please either edit these down or only post a link to the original.

Posted by: serpens Nov 27 2012, 11:18 PM

QUOTE (mcaplinger @ Nov 27 2012, 06:21 AM) *
http://www.lpi.usra.edu/meetings/lpsc2012/pdf/2008.pdf and various other abstracts coming up with a google search for "sam msl perchlorate" may be of interest.

Thanks for the link and as expected I stand corrected on the Ca perchlorate decomposition products. The sheer volume of information on the web is daunting but I couldn't find anything on analysis of mixed samples reflecting candidate martian perchlorates/soil compositions? I seem to remember that the thermal stablility of a mix of perchlorates is lower than that of the pure components and the initial endothermic reaction in the figure 1 Wicked Witch sample seems closer to that for Ca perchlorate. Curiosity's investigative capability is remarkable and I can't wait for the next LPSC.

Posted by: Lucas Nov 28 2012, 04:57 PM

Well, this is interesting... apparently all the hype was simply due to a misunderstanding by the NPR reporter who was interviewing Dr. Grotzinger!

http://www.slate.com/blogs/the_slatest/2012/11/27/nasa_mars_discovery_misunderstanding_mission_leader_excited_about_entire.html

A tweet by Curiosity (screenshot attached) was meant to reduce the expectations and clarify Dr. Grotzinger's remarks, but apparently it wasn't noticed and the story went viral.

Sigh...

--Lucas


 

Posted by: fredk Nov 28 2012, 07:28 PM

It certainly does look like bad reporting, at least in part. Remember that the word "earthshaking" was used in http://www.npr.org/2012/11/20/165513016/big-news-from-mars-rover-scientists-mum-for-now. However, it was not directly quoted to Grotzinger. Now that word has been quietly changed to "remarkable".

Posted by: EdTruthan Nov 29 2012, 08:58 PM

Press release on the Dec. 3rd AGU press conference in San Francisco just posted http://www.jpl.nasa.gov/news/news.php?release=2012-377&cid=release_2012-377. The gist of the statement reads:

"Rumors and speculation that there are major new findings from the mission at this early stage are incorrect. The news conference will be an update about first use of the rover's full array of analytical instruments to investigate a drift of sandy soil. One class of substances Curiosity is checking for is organic compounds -- carbon-containing chemicals that can be ingredients for life. At this point in the mission, the instruments on the rover have not detected any definitive evidence of Martian organics."

Posted by: marsophile Dec 3 2012, 05:43 PM

I have video but no audio of the press conference. It appears from the graphics that chlorinated hydrocarbons have been detected. Those were also detected by Viking almost 40 years ago but were attributed then to contamination by cleaning fluids.

Posted by: fredk Dec 3 2012, 06:04 PM

Details at the http://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1399 if anyone hasn't seen it already.

Posted by: dvandorn Dec 3 2012, 06:59 PM

And yet the media still hear what they want to hear...

http://www.huffingtonpost.com/2012/12/03/organics-on-mars-curiosity-rover_n_2232436.html

sigh...

-the other Doug

Posted by: Hungry4info Dec 3 2012, 07:02 PM

Well, in fairness, they did say they detected simple organics, but they couldn't be sure it wasn't from the rover.

Posted by: silylene Dec 3 2012, 07:14 PM

The chlorinated methanes are interesting. CH3Cl, CH2Cl2, and CHCl3 were detected.

If the starting C-containing material was CO2, somehow the C would have to be reduced, and a source of H would also be needed (from the decomposition of water, presumably?). It is not a simple process to reduce the C in CO2. However, i want to point out that some metal oxide dusts can function as capable catalysts for CO2 reduction (this is an active area of chemical research!).

For example a potential heat assisted catalytic cycle using a metal oxide, (unbalanced reaction):
H2O + CO2 + MOn + heat --> H2 + CH4 + CO + MOn+2
MOn+2 + heat --> MOn + O2

The CH4 is then subject to free radical chlorination, from a perchlorate origin.

Did the press conference presentation say whether they also detected CH4 or CO ? If my above mechanism is correct, then CH4 should have been found too, probably in greater amounts than the CH3Cl. If not, why not? I doubt that CH4 was not present if the chlorinated methanes were seen. I do note that they did detect O2. Of course the O2 could have come from the perchlorate, or my mechanism, or both. Someone needs to do a careful mass balance !

I may need to work out an alternate pathway using a sulfur compound as my reducing agent. The link does say that sufides may have been involved, these can be oxidized to SO2. H2S and SO2 were detected. http://www.jpl.nasa.gov/spaceimages/details.php?id=pia16575

Now I can understand why Grotzinger got excited: Perhaps he at first thought he had a biogenic source of CH4. But abiogenic sourced CH4 is much more likely, in my opinion, perhaps via a reaction pathway similar to this outline.

Posted by: serpens Dec 3 2012, 10:07 PM

QUOTE (dvandorn @ Dec 3 2012, 07:59 PM) *
And yet the media still hear what they want to hear...


Or maybe the fault lies with the left hand right hand disconnect from the team rather than with the media.

Paul Mahaffy, SAM principal investigator said "SAM has no definitive detection to report of organic compounds,"

John Grotzinger said "Even though [Mahaffy's] instrument detected organic compounds, first of all we have to determine whether they're indigenous to Mars"

Did they get a definitive detection of organics or not? Perhaps the British approach of a nice cup of tea and a chat to agree the findings would be beneficial. Organic molecules from infall would be expected, effectively compulsory, although the use of terms like 'indigenous to Mars' give rise to unfortunate implications for provenance.

Posted by: MahFL Dec 3 2012, 10:58 PM

QUOTE (dvandorn @ Dec 3 2012, 06:59 PM) *
And yet the media still hear what they want to hear...

http://www.huffingtonpost.com/2012/12/03/organics-on-mars-curiosity-rover_n_2232436.html

sigh...

-the other Doug


Why the sigh, they report accurately in the article the current situation. Everyone needs a headline, that is what pays their mortgage......

Posted by: mcaplinger Dec 3 2012, 11:06 PM

QUOTE (serpens @ Dec 3 2012, 03:07 PM) *
Paul Mahaffy, SAM principal investigator said "SAM has no definitive detection to report of organic compounds,"

The press release says "We have no definitive detection of Martian organics at this point, but we will keep looking in the diverse environments of Gale Crater," said SAM Principal Investigator Paul Mahaffy..." (italics mine.)

The question is whether any detected organics are from instrument contamination or from the surface. Presumably at some point they will run the Organic Check Material through the system to address this.

I agree that this has not been a PR triumph. IMHO the best course would have been to say nothing until there was more definitive news, but with media attention this is easier said than done.

Posted by: nprev Dec 3 2012, 11:08 PM

The discontinuity seems to be:

1. "Organics" was not precisely defined. That's a charged word, obviously. However, they did effectively communicate the fact that complex organic compounds most likely have meteoritic origins till proven otherwise, and even cited the recent Messenger findings on Mercury as an evidence that such compounds are far from uncommon throughout the Solar System.

2. The 'organics' thought to be detected seem to be most likely evolute products from the sample heating (i.e., chloronated methane). Several references to 'single carbon' compounds...well, so is CO2. Judgement call.

Bottom line from my perspective: SAM & the other instruments seem to be working well. This was pretty much a first-grab sample from a dune, so not much should be expected given that dunes usually consist of windborne (not necessarily local) material; it's gonna be light stuff no matter what.

Now let's see if we find some phyllosilicates... smile.gif




Posted by: Antonb Dec 4 2012, 02:24 PM

Not only was 'organic' not precisely defined in yesterday's conference, the word cannot be defined with any scientific precision. Organic originally meant relating to an organism, a living entity. These days, people most often see the word organic on meat & veg in the supermarket. Has anyone ever seen an inorganic cow or cabbage?

Astronomers say there are organic compounds to be found all over the universe, even in the rocks that fall from space onto Earth, Mars and everywhere else, but they don't intend to imply that these originated in an organism. Yesterday's NASA press release defined organic compounds as "carbon-containing chemicals that can be ingredients for life". There is no scientific consensus behind this definition. For some, if a compound includes carbon, it's organic. Others require a C-H bond, but then that excludes common bodily compounds such as urea. As if that weren't confusing enough, astronomers don't call CO2 an organic compound, even though it's unquestionably a carbon-containing chemical that's an essential ingredient for life.

To be fair, I thought yesterday's conference did an excellent job explaining that the various compounds detected could have numerous explanations and that only painstaking, patient, scientific method will determine the answer. The co-ordinated, multi-instrument analyses they revealed are a spectacular achievement, but you could sense there was some discomfort and embarrassment on the platform, especially when the press kept returning to that darn word organic.

This linguistic inexactitude is the root cause of the wild speculation about "Life on Mars" that springs up just as soon as the word organic is mentioned. The word is functionally useless in any scientific context. Worse yet, it's not even necessary.

Among the many things that the MSL team have discovered so far are carbon compounds. They cannot yet say whether these carbon compounds are biotic or abiotic in origin.

Posted by: JRehling Dec 4 2012, 03:27 PM

If you currently do a Google News search for "mars curiosity" it's easy to browse headlines, and the contradictory takeaways this event produced are evident. While the main articles may or may not converge by giving the same nuanced explanation, the headlines swing wildly from "detects 'organic compounds'" to "sees... no organics." Yesterday, in the body of one article, I saw a claim that the organics might have been brought to Mars by Curiosity (which is right) but then added the possibility they were brought by some previous spacecraft, which given the distances between landing sites is outrageously wrong and suggestive of something wild!

My dog used to take any jingle of my keys as a sign that we were going for a walk, and would become agitated and persistent if she heard the jingle. It didn't take me long to learn not to jingle them unless a walk was imminent. The scientific establishment would do well to know how the dog (media, public) responds to jingle and to act accordingly. In this busy, information-packed world, headlines have a powerful currency, we must all choose which headlines we read past and which we learn from, and this was, as others have noted so well, a case which was treated appropriately when the scientists had time in a panel discussion to explain things clearly, but the first "jingle" was careless.

I understand why there's excitement around the mere detection/non-detection of carbon in martian soil, but at the same time, carbon is the THIRD most abundant element in the solar system if you exclude helium (which is certain not to be a major bulk component of Mars) and the second most abundant element in Mars's atmosphere. In fact, there have to be some damned good reasons if we don't find any carbon in martian soil, which there obviously are (on Earth, as well, it is only 15th in crustal abundance). Which is just to say that finding it or not should have been (and should be, going forward) flagged in advance as a possible media event to treat according to a sensible key-jingling protocol. Without the team ever having misled anyone in a deliberate sense, there was a real, though unintended head-fake of the first degree here. News!?!?!? No, not in the sense that grabs first-page headlines. And the trust and attention erodes a little bit.

Meanwhile, Venus Express may have found signs of a volcanic eruption on Venus, and hardly a whisper in the news... In the (striking!) event that in one week we have news concerning one substance or another at all three planets in the inner solar system, I'd say the Mercury case was handled perfectly, the Venus one with too little hoopla, and the Mars one with far too much.

Posted by: Fran Ontanaya Dec 4 2012, 04:40 PM

Can we go back to discussing the actual results. None of these science vs media issues are new. Most people I know expected the "stuff that isn't like boring rock minerals", and that's what they announced.

Posted by: marsophile Dec 4 2012, 04:43 PM

For some context, we had the following results from the Viking GCMS.
Sample T Compound Abundance (ppb)
VL1
Blank Test 500 CH3Cl Not Detected
Sample 1 200 CH3Cl 15
VL-2
Blank Test 500 CH2Cl2 Not Detected
Sample1 500 CH2Cl2 2-6
Sample2 500 CH2Cl2 20-40

For a discussion, see this paper:
http://www.agu.org/pubs/crossref/2010/2010JE003599.shtml

The original Viking GCMS results were published in this Ph.D. thesis:
http://dspace.mit.edu/bitstream/handle/1721.1/16069/07517313.pdf

See for example, Pages 203 and 204 for VL-1 and VL-2 chlorinated hydrocarbon results.
(Methyl Chloride = Chloromethane, Methylene Chloride = Dichloromethane)
Also chlorinated hydrocarbon results from Antarctic soils Pp 233,242,250,258.

Posted by: Don1 Dec 5 2012, 02:01 AM

I think we're looking at a work in progress with the SAM results. They don't really have publication grade scientific results but they do have some very interesting data and hypotheses.

The most interesting is the detection of the chlorinated hydrocarbons, which are mostly chloromethanes. These showed up in Viking results on Mars, but were not seen in pre-flight tests of the Viking instrument. Chloromethanes are good solvents and cleaning agents. For instance CCl4 is used for dry cleaning. The Viking results were written off as contamination of the sample handling system by cleaning agents.

After the discovery of perchlorates, Chris McKay pointed out that a perchlorate containing soil would convert any organics it contained into chloromethanes on heating. He suggested that Viking did indeed detect Martian organics, but that the data was misinterpreted because the presence of perchlorate in the soil was unknown at the time.

I think the detection of chloromethanes by SAM puts a big question mark over the interpretations of Viking data, including the Viking conclusion that the Mars soil did not contain organics. The non-detection of organics by Viking was a very important result that drove the interpretation of some of the odd data produced by the other experiments.

However, SAM still has contamination issues of their own to sort out, including evidence that the rover is shedding plastic on the soil and hints that there might be a leak of organic reagent inside the instrument. People are also suggesting ways to make chloromethanes from purely inorganic reagents like CO2, water and perchlorate. So at this point there are viable hypotheses that explain the data without needing Martian organics. Only time will tell which is correct.

Posted by: djellison Dec 5 2012, 02:20 AM

QUOTE (Don1 @ Dec 4 2012, 06:01 PM) *
I think we're looking at a work in progress with the SAM results.


Errr - obviously. They said as much yesterday.

Posted by: serpens Dec 5 2012, 08:32 AM

QUOTE (Don1 @ Dec 5 2012, 02:01 AM) *
The most interesting is the detection of the chlorinated hydrocarbons, which are mostly chloromethanes. These showed up in Viking results on Mars, but were not seen in pre-flight tests of the Viking instrument.


As identified in the thesis linked by marsophile in post #44, (page 197) these chlorinated molecules were revealed in tests conducted on the spare flight instrument using the entire system. They would not have been seen in the pre flight oven checks or the flight blank tests and would only have contaminated a real run. Could additional chlorinated species have been produced as well as the contaminants? Certainly, and the SAM result indicates that maybe perhaps this could be so, but I think I want to see a heap more test results before drawing an conclusions or comparison to Viking results.

Re organic, none of us have problems with understanding homonyms in context , identical words with different meanings such as peer, rose, engaged etc. Lets all get over it.

Posted by: marsophile Dec 5 2012, 04:03 PM

QUOTE (marsophile @ Dec 4 2012, 09:43 AM) *
Also chlorinated hydrocarbon results from Antarctic soils Pp 233,242,250,258.


What I find fascinating is that chloromethanes were detected by tests of the Viking GCMS in Antarctic soils.

Apparently these soils do also contain perchlorate:
http://pubs.acs.org/doi/abs/10.1021/es9033606

If this hint had been followed up, we might have hypothesized the presence of perchlorate in Martian soils a lot earlier.

Posted by: dvandorn Dec 5 2012, 04:59 PM

QUOTE (marsophile @ Dec 5 2012, 11:03 AM) *
...If this hint had been followed up, we might have hypothesized the presence of perchlorate in Martian soils a lot earlier.

Well... perchlorate was one of the options that was being discussed at the time of the original GCMS experiments on Viking. The phrasing I recall is that the time-release experiment data fit well with a Martian soil rich in "super-oxidants," and one of the super-oxidants that headed the list was perchlorate. I believe the presence of chlorine in some of the evolved gasses seen in the Viking results is what led to that speculation, 36 years ago.

I don't have any articles of the time in front of me, but I am very confident of my memory of the "super-oxidant" reports.

-the other Doug

Posted by: silylene Dec 5 2012, 07:29 PM

As I suggested in my prior post in this thread, I think the chlorinated methanes could have been produced from free radical reaction of the decomposition products of perchlorate with methane; with the methane formed in situ by the catalytic hydrothermal reduction of CO2 with high heat (oven max temp one oven = 950C the other oven = 1100C) over metal oxide containing dusts (certain metal oxide dusts can be catalysts for the hydrothermal reduction of CO2 to methane). H2O came from water adhering to silica grains. Alternatively, instead of a hydrothermal reduction of CO2, the redox reaction to form CH4 could have been run from H2S --> SO2. Both H2S and SO2 were detected.

I am wondering if CH4 or CO was detected in the gas stream evolved from the oven. Either would lend strong support to this hypothesis.

Posted by: mcaplinger Dec 5 2012, 07:51 PM

QUOTE (dvandorn @ Dec 5 2012, 09:59 AM) *
Well... perchlorate was one of the options that was being discussed at the time of the original GCMS experiments on Viking. The phrasing I recall is that the time-release experiment data fit well with a Martian soil rich in "super-oxidants," and one of the super-oxidants that headed the list was perchlorate.

I don't think so. At the time H2O2 or superoxides were used as explanations for the O2 release seen after wetting in the GEx experiment, and CO2 release in the LR experiment. I'm no chemist but I don't think perchlorates alone explain these results; see http://www.lpi.usra.edu/meetings/lpsc2011/pdf/2003.pdf for example. And I don't think that perchlorates are technically superoxides.

I'd be happy to be proved wrong but it would take an actual reference from pre-Phoenix to convince me that anyone had mentioned perchlorates in the context of Viking.

Posted by: NickF Dec 5 2012, 08:47 PM

QUOTE (mcaplinger @ Dec 5 2012, 01:51 PM) *
And I don't think that perchlorates are technically superoxides.


You'd be correct to think this. Perchlorates are undoubtedly good oxidants (although there are kinetic barriers to their activity due to steric hindrance of the central chlorine atom), but they are not superoxides. Perchlorates can undergo autoxidation to form superoxide in the presence of O2.

Posted by: mcaplinger Dec 5 2012, 08:59 PM

QUOTE (mcaplinger @ Dec 5 2012, 12:51 PM) *
...it would take an actual reference from pre-Phoenix to convince me that anyone had mentioned perchlorates in the context of Viking.

For example, Zent and McKay's 1994 Icarus paper "The Chemical Reactivity of the Martian Soil and Implications for Future Missions" http://www.sciencedirect.com/science/article/pii/S0019103584710475 says nothing about perchlorates that I can see.

Posted by: marsophile Dec 6 2012, 04:18 AM

One thing that seems puzzling is why chloromethanes were not detected by the TEGA instrument on Mars Phoenix. These two papers, proposing reactions with calcite and nickel, respectively, provide possible answers:

https://docs.google.com/viewer?a=v&q=cache:sqb3tlOK8ZAJ:ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120000902_2012000960.pdf+&hl=en&gl=us&pid=bl&srcid=ADGEESjUB5olRgAIKR2DmSe5FBvh419I2PiAeof_xVelEEqEG50fq-lbbsTmRW9EqmtLZSePkWsv1NLD-EJ5OZpOE9Pa7T0RSTdXrjCblLUGhG19TazRDY4tMTEHfgGj_0ogiU2Xk-Wu&sig=AHIEtbSnWuNKDEGporrm5mP8BGPFzw7JXA

https://docs.google.com/viewer?a=v&q=cache:fxYrFFdFnYcJ:ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090010369_2009009665.pdf+&hl=en&gl=us&pid=bl&srcid=ADGEESj5iyGvBOY0I11GoHJZR-4sNBnHEFPwF0-panzZZQjt95peS8fpsxhJvRWzftQQFcfzKpQyoKCQCwBJnVBgvoAG2zJgJq6o9RK6doqwae-z4PEg2bWG8IOOLnhQkF6NB6Aiatqw&sig=AHIEtbS0V8qKYUhziCkOC2KmIlYeHNnaWA



Posted by: Don1 Dec 6 2012, 09:10 AM

Elements like potassium and sodium have several different oxides. There is the oxide, the peroxide, and the superoxide. Potassium superoxide (KO2) was suggested to explain the results form Viking.

Hydrogen peroxide (H2O2) was also suggested to explain the Viking results.

Unrelated to superoxides, there is a whole family of oxy-chlorine ions, going by the names of hypochlorite, chlorite, chlorate and perchlorate. They feature from one to four oxgen atoms bonded to each chlorine. Perchlorate has four oxygens. Perchlorates on Mars never got much attention before Phoenix.

The non-detection of chlorine containing species by Phoenix requires an explanation. The paper linked above says that chlorine will react with the nickel which the oven was made of.

Posted by: stone Jan 31 2013, 10:47 PM

QUOTE (dvandorn @ Dec 5 2012, 05:59 PM) *
Well... perchlorate was one of the options that was being discussed at the time of the original GCMS experiments on Viking. The phrasing I recall is that the time-release experiment data fit well with a Martian soil rich in "super-oxidants," and one of the super-oxidants that headed the list was perchlorate. I believe the presence of chlorine in some of the evolved gasses seen in the Viking results is what led to that speculation, 36 years ago.

I don't have any articles of the time in front of me, but I am very confident of my memory of the "super-oxidant" reports.

-the other Doug


I looked for an article on perchlorates on mars prior to the 1990s and I cold not find anything, do you have a hint were to look?

There are only two mentioning mars and perchlorates at all.

http://dx.doi.org/10.1016/0019-1035(78)90052-0
http://dx.doi.org/10.1016/0019-1035(81)90041-5

Thanks

Posted by: mcaplinger Feb 1 2013, 12:17 AM

QUOTE (stone @ Jan 31 2013, 03:47 PM) *
I looked for an article on perchlorates on mars prior to the 1990s and I cold not find anything, do you have a hint were to look?

I don't believe there are any, see post #51 and following.

Posted by: stone Feb 1 2013, 06:59 AM

ADMIN TIP: When replying to a post immediately preceeding yours, use the "Add Reply" or 'Fast Reply" button and not the "Reply" button. smile.gif

This is what I thought.

The perchlorates make it very difficult to get good data from the SAM instrument. The chlorine and oxygen generated at temperatures above 250°C have a very destructive influence on most of the organic material.
I hope that the perchlorates are concentrated in the dust and that the rocks had no mechanism to get soaked up with the perchlorates.

Posted by: Gerald Feb 1 2013, 07:11 PM

For the 44th Lunar and Planetary Science Conference (2013) the abstract http://www.lpi.usra.edu/meetings/lpsc2013/pdf/2168.pdf is already available. Old Viking results are also discussed.

Posted by: stone Feb 1 2013, 09:16 PM

With the Viking data showing chlorohydrocarbons and looking back it looks very much like a part of this was created by the same mechanism observed in the SAM instrument. This makes it look like there was perchlorate at the two Viking landing sites on the one for Phoenix and at MSL. So the perchlorates are everywhere. The Biemann Navarro-Gonzales dispute on the Viking results may go into the second round.

Posted by: marsophile Feb 1 2013, 09:29 PM

The cited paper allows for the possibility that the organic material that contributed to the chlorinated hydrocarbons was contamination from Earth (as did an MSL press briefing).

If one assumes that the supply of any organic contamination from Earth is finite and limited, then repeating the measurement a number of times should provide some insight into this issue: If the quantity of chlorinated hydrocarbon decreases steadily, that would tend to indicate contamination. A residual quantity might indicate an indigenous source.

Posted by: Don1 Feb 2 2013, 09:28 AM

Yes there is news from SAM and it ain't good. The leak from the wet chemistry cells is far more serious than they let on and as a result the data on organics from Rocknest is useless. They are seeing 100 times as much chloromethanes as Viking did, but the trouble is that all or most of it is coming from the reaction between the wet chem reagent and the perchlorates in the soil. Any Martian signal is completely drowned out. To quote the scientists: "Thus, at this time, while MTBSTFA contamination can explain all of the chlorohydrocarbons observed, we cannot exclude the possibility that traces of martian organics contributed to the chloromethanes measured by SAM."

The MTBSTFA leak looks like a serious problem which is going to reduce SAM's capability to detect Martian organics.

Data from http://www.lpi.usra.edu/meetings/lpsc2013/pdf/1080.pdf

Posted by: stone Feb 2 2013, 11:12 AM

QUOTE (marsophile @ Feb 1 2013, 10:29 PM) *
The cited paper allows for the possibility that the organic material that contributed to the chlorinated hydrocarbons was contamination from Earth (as did an MSL press briefing).

If one assumes that the supply of any organic contamination from Earth is finite and limited, then repeating the measurement a number of times should provide some insight into this issue: If the quantity of chlorinated hydrocarbon decreases steadily, that would tend to indicate contamination. A residual quantity might indicate an indigenous source.


The derivatization reagent MTBSTFA leaks slowly and will not go away in the sealed enviroment of SAM. SAM is a box with nearly no openings. The article of Arno Buch is describing the reactions of the MTBSTFA and they are not aproblem in its own, as long as the perchlorate is not everywhere. The perchlorates will make it very difficult to determin where the organic carbon is coming from. The chlorinated methanes can come from nearly every source.

Posted by: marsophile Feb 3 2013, 01:38 AM

Couldn't they simply use up the supply of the derivatization reagent MTBSTFA by using it for the purpose for which it was intended?

Posted by: stone Feb 3 2013, 07:16 AM

The MTBSTFA is used to search for amino acids and other not tha volatile compounds. The detection limit is a lot increased if you convert them to the sililylated compounds. This will be done when a measurement with the normal ovens shows at least some organics. SAM does not have a lot of those derivatisations ovens and in the end they could lose a significant science return (mostly related to a field of research forbidden to mention here) if they do not have the MTBSTFA anymore.

One further point is that the compound is not very volatile and if it is everywhere in the SAM box already using the rest might not improve the situation a lot.

ADMIN NOTE: The astrobiology rule is well understood on the Forum and therefore there is no need to mention that it should not be mentioned.

Posted by: marsophile Feb 4 2013, 03:41 AM

Then it seems there is a catch-22 situation: They can't detect native organics because of the MTBSTFA contamination, and they won't use the MTBSTFA until they detect native organics.

If the contamination is worsening with time, then maybe it should be jettisoned as soon as possible since it seems it won't be used for its intended purpose anyway?

Posted by: stone Feb 4 2013, 07:53 AM

QUOTE (MrNatural @ Nov 23 2012, 04:08 PM) *
Can we discuss SAM's stereochemistry capabilities?

SAM's stereochemistry capabilities lie within the GC. The mass spectrometer is blind for chirality, because it can only measure weight. The enantiomeres have to be separated within the GC. To do that the stationary phase in the columns has to be a chiral substance too. Only chiral compounds interact with each other in a way that there is a difference between the enantiomeres. One of the columns in sam is a GC4-Chirasil-β Dex CB . The column material is a β-cyclodextrin a cyclic sugar The β-cyclodextrin rings contain several glucose molecules all of them contain several chiral carbon atoms.

Most of the compounds here on earth necessary for biochemistry like sugars, amino acids and nucleo base are a real horror in GC, they are instable at high temperatures and contain a lot of O-H and N-H bonds making them capable to build up strong hydrogen bonds to each other. This hydrogen bonds lead to high boiling points and therefore high temperatures to get them into the gas phase to get them through the gas chromatograph. To overcome this derivatization reagents are used to substitute the hydrogen at the OH and NH groups by sillyl or methyl groups. MTBSTFA and DMFDMA and TMAH are possible compounds for this. In SAM this derivatization is done in the wet chemistry cells. All the resulting derivatized material is then put onto the chiral column and into the GC.

In the end you see in the GC plot two peaks very close to each other with exactly the same patern in the MS. With the peak area you can determine if one of the enantiomeres is more abundant than the other. One problem with this is the fact that racemesation, the chemical reaction of converting one pure enantiomere into a 50/50 mixture is fast for a lot of the compounds you are looking for. Even normal garden soil shows sometimes not the 100% R or S what you would expect from the text book knowledge.

Posted by: Mr Valiant Feb 4 2013, 11:27 AM

I had no idea that the GC was so, so...definative. I read the Wiki article 'Isotopic labeling', a good primer.
Hope the leak issues can be resolved, an amazing instrument.

Posted by: marsophile Feb 11 2013, 06:03 AM

Drilling is probably the best bet for getting a perchlorate-free sample into the ovens.

Best of all might be drilling into a gypsum vein. A gypsum deposit precipitated from water would be unlikely to contain perchlorate (since perchlorate is much more soluble than calcium sulfate) and might have trapped some material with organic chemicals.

In future missions, the simplest method of removing perchlorate from soil samples might be to wash them in sterilized pure water before heating them.

Posted by: stone Feb 11 2013, 07:43 AM

If the perchlorates are ancient the vein should be free of perchlorates.

My little horror story would be:

The formation of the perchlorates by radical process involving water, inorganic chlorides and UV radiation would make them evenly distributed in the Martian dust since the beginning of Mars. Magnesium and calcium perchlorate are hygroscopic and a little bit of moisture creates a brine. So the first perchlorates rained down 3 -4 Gyears ago and from time to time the axis tilts and the polar caps move and every point on Mars gets a little moisture over 3-4 Gyears and the perchlorates are transformed into a brine which soaks into the small cracks of all surface rocks up to a depth were ground water is possible. With that the perchlorates every where except at points which are enclosed from any water intrusion.

I hope for a perchlorate free sample but the 5cm subsurface could be a few meters to few to get a perchlorate free sample.

Posted by: rickyjames Feb 15 2013, 02:41 PM

Could somebody please elaborate on the statement made several weeks ago that the SAM unit has a serious leak in its stored reagents? Where is a link or reference to what has been stated publically about this issue by the mission team?

Posted by: stone Feb 15 2013, 05:07 PM

"Although none of them have been punctured yet for the actual wet chemistry experiment, it is suspected that one or more may be releasing some of its reactant. "http://www.lpi.usra.edu/meetings/lpsc2013/pdf/1249.pdf FROM BACKGROUND TO SIGNAL: CHALLENGES OF A SOLID SAMPLE ANALYSIS USING SAM GC-MS

Posted by: marsophile Mar 9 2013, 02:40 AM

If the SAM and CHEMIN instruments performed measurements on a random mudstone on Earth, what would be the probability that they would detect organics?

Posted by: stone Mar 9 2013, 10:52 AM

The heating like done by SAM is not done often on rock samples here on earth. So there is limited data most of it would have been in the SAM team. The mud stones especially if it is a layered structure have been shown to preserve organics but also bind the organics very well in the layered structures. If you chose the random mudstone well then SAM might not find anything. In most mudstones SAM would detect organics. For Amino acids and nucleo base the whole thing is very complicated. Only the SAM team knows to what extent the derivatisation will improve the situation. The silicates with large surface area also tend to be catalytic for numerous chemical reactions.

If CHEMIN will detect organics something very strange has happened. Crystals of organic material must be the main compound of the modstone. Carbon is a light element and does not give good x-ray diffraction, heavy elements work much better.Wikipedia gives a few examples of organic crystalline minerals. Carpathite is one of them. If this is the main compound of the sample SAM would be in deep trouble by the organic overload.

Posted by: jmknapp Mar 9 2013, 11:11 AM

Check this report of SAM tests on Earth:

http://solarsystem.nasa.gov/news/display.cfm?News_ID=16735

...where SAM detected organics in a couple different deposits, not mudstone exactly though if I read it right, unless dolomite is considered a mudstone.

Posted by: stone Mar 9 2013, 04:44 PM

I know what the SAM team had at AMASE in 2010 and this was not a flight spare of SAM. This article is from 2006 and so I doubt that the machine was a 100% representative for SAM. Adn I doubt that they would write in an article that they encountered a rock which looked empty but in fact had organics.

I am sure that they also encountered some rocks which looked empty, so it is very dependent on the rock. There are mudstones which are nearly organic free and with those even SAM would have difficulties.

The amount of organic they need for a detection is very low and a most mudstones here on earth would give a nice signal.


Posted by: Don1 Mar 10 2013, 09:38 AM

Many Mars meteorites contain organics at levels that are very detectable by SAM. Amino acids at 100ppb levels have been reported. There is some controversy over the origin and these might be terrestrial. A high temperature Martian origin seems to be the favored explantion. Levels of reduced carbon in the 1-50 ppm range have also been reported, and this would be easily detected by SAM.

The bottom line is that there is a good chance that SAM will detect traces of organics in the next few months if it hasn't already. IIRC the detection limit for SAM is 1ppb organics.

http://www.lpi.usra.edu/meetings/lpsc2013/pdf/2613.pdf

http://www.lpi.usra.edu/meetings/lpsc2013/pdf/2613.pdf

Posted by: stone Mar 10 2013, 10:14 AM

The detection level is a very complicated topic for all pyrolysis based systems. It is hard to determine the exact numbers because the extraction efficiency of pyrolysis is depending on:

*the chemistry of the rock; oxidative and reductive compounds will have a significant influence catalytic surfaces will influence the result

*the distribution in the rock; strongly encapsulates org. molecules or strongly adsorbed org. molecules are hard to get out of the rock

*the compound; there are compound which decompose very easy into CO, CO2 and N2 and you will not see an organic molecule at all the same for the kerogenic substances which are hard to detect because of the high boiling points.

The comparison with extraction techniques often shows you that what you expected is a lot different in reality.

With the 1ppb detection level there will be hardly a chance that they will not detect anything in the coming months of the mission. If they find nothing in the next few years Mars has an unknown mechanism to get ride of organics.

Posted by: xflare Mar 10 2013, 10:50 AM

But don't we already know Mars has/had organics - from Martian meteorites?

Posted by: t_d Mar 10 2013, 01:11 PM

QUOTE (xflare @ Mar 10 2013, 06:50 AM) *
But don't we already know Mars has/had organics - from Martian meteorites?


Yes, from:
http://www.lpi.usra.edu/meetings/lpsc2013/pdf/1476.pdf

Posted by: fredk Mar 10 2013, 03:22 PM

QUOTE (Don1 @ Mar 10 2013, 09:38 AM) *
there is a good chance that SAM will detect traces of organics in the next few months if it hasn't already. IIRC the detection limit for SAM is 1ppb organics.

But we don't know what effect the MTBSTFA leak will have, right?

Posted by: centsworth_II Mar 10 2013, 05:36 PM

QUOTE (xflare @ Mar 10 2013, 05:50 AM) *
But don't we already know Mars has/had organics - from Martian meteorites?

See Don1's post 77. The pressing question is whether Curiosity will find organics and if so, what her instruments will tell us about them.

Posted by: Don1 Mar 10 2013, 08:17 PM

QUOTE (fredk @ Mar 10 2013, 07:22 AM) *
But we don't know what effect the MTBSTFA leak will have, right?


The effect of the leak depends upon the presence of perchlorates in Martian rocks, which Tuesday's briefing should discuss. Hopefully they won't be found.

If perchlorates are present, well SAM has a big bag of tricks and some of those can be used to deal with the problem. The wet chemistry cells can react away the perchlorate and enable the detection of organics that might be present. There is a very limited supply of those cells, perhaps more limited now that some have leaked.

Posted by: stone Mar 10 2013, 09:46 PM

The MTBSTFA gives you a nice background and makes the search for the very small peaks more difficult. All the spots of large peaks you lose for your science. The perchlorate gives you another bunch of peaks, the small mono- di- and tri-chloromethanes. With the knowledge that perchlorates oxidise a lot of the present organics and transforms another share to chlorohydrocarbons you now have to guess how much of the chlorohydrocarbons you detect are from the MTBSTFA or from some other source. So the leak of MTBSTFA or the use to save the organics from the perchlorates makes analysis complicated and gives you a headache to make the case that you really have found something.

I hope for perchlorate free sample at some point of the mission.


I expect nothing special, like life on Mars or abundant organics, on Tuesday!


Posted by: Cardinal Mar 11 2013, 08:28 PM

From what I can tell, the actual press conference in Washington is out of the ordinary. Maybe they really did find something? Likewise, I do not expect life on Mars, but I would imagine they have a high level of confidence in their data to deviate from the normal method of releasing their results.

Posted by: nprev Mar 11 2013, 08:43 PM

Repeat: Don't get too excited. This will be an announcement about the first-ever chemical composition derived for a Martian rock, and probably a victory lap for the SAM team since the instrument will have been proven to operate properly (to say nothing of the complex drilling/sorting arm hardware).

I'd wager that the presser will be 90% milestone achievement, 10% findings.

Posted by: belleraphon1 Mar 11 2013, 09:24 PM

Agree with nprev.

Analysis by CheMin and SAM of a drilled sample is a major milestone for Curiosity, whatever the result.
That in itself would merit the T.V. briefing from NASA HQ.

Looking forward to whatever is presented.

Craig

Posted by: xflare Mar 11 2013, 09:45 PM

QUOTE (nprev @ Mar 11 2013, 08:43 PM) *
Repeat: Don't get too excited. This will be an announcement about the first-ever chemical composition derived for a Martian rock, and probably a victory lap for the SAM team since the instrument will have been proven to operate properly (to say nothing of the complex drilling/sorting arm hardware).

I'd wager that the presser will be 90% milestone achievement, 10% findings.


But the SAM and Chemin instruments and not to mention the complex CHIMRA sorting mechanism were all proved to be working many months ago at rocknest. To be honest im more interested in a update on MSL's operational status right now - what's the deal with that anyway? huh.gif

Posted by: jmknapp Mar 11 2013, 09:56 PM

True--in terms of announcing subsystem firsts, they kind of declared everything working at the last telecon. I hope that reporters ask about the current status of the computer.

Posted by: Don1 Mar 12 2013, 09:24 PM

Today's announcement looks like a mixture of good and bad news. The good news is that habitability potential is high. There is liquid water which is close to neutral and not too salty. There is food. There are nutrients like nitrogen and phosphorous. There are clays which are good for trapping organic matter, and the environment is not highly oxidizing. The one remaining issue is how persistent the wet conditions were. The geologists indicated that the wetness might have been intermittent, but they didn't rule out a long lived lake, which would be much better for habitability.

The bad news is that the rocks contain perchlorate, which will make detecting organics much more complex and ambiguous. Perchlorate is extremely soluble, so it was likely washed into the rocks by groundwater long after the rocks formed. SAM has a big bag of tricks, so we will have to wait and see what the instrument can do with this sample.

The D/H ratio seems to be a lot different from modern values, so that points to an old deposit. It will be compared to Martian meteorites, and with luck it may provide a relative age for Glenelg.


Posted by: marsophile Mar 12 2013, 10:15 PM

Did they specifically identify perchlorate, or is that inferred from the chlorinated hydrocarbons?
Would water percolating through rocks really deposit (very soluble) perchlorate, or wash it away?
AFAIK, rocks on Earth do not contain substantial perchlorate.

HCl was mentioned, so maybe that was the source of the chlorination? Or maybe perchlorate from some of the soil left over from Rocknest?

At least now the level of chlorinated hydrocarbons is way above the blank background.

Posted by: fredk Mar 12 2013, 11:12 PM

All I remember is a statement that they saw perchlorate and no further details. Maybe someone else caught more?

Posted by: Don1 Mar 13 2013, 02:10 AM

They see oxygen released at a temperature consistent with perchlorate decomposition and they see the production of chlorinated hydrocarbons.

They did mention that they had tried to flush the leaked reagent out of the system by preheating the sample for 20 minutes.

Posted by: t_d Mar 13 2013, 03:20 AM

Wouldn't heating the sample for twenty minutes drive off other interesting compounds and molecules?

Posted by: Phil Stooke Mar 13 2013, 03:26 AM

Yes, and they measure them all.

Phil


Posted by: centsworth_II Mar 13 2013, 04:22 AM

Here is a transcript of SAM PI Paul Mahaffy's response to a Craig Covault question (at 48:30):

"In the rocknest sample we certainly detected some vapor that was very easily identifiable. A trace amount of vapor -- nanomoles -- that's a signature of what's inside our wet chemistry cells. And so one way or another, whether it was through a very small leak through one of the pinch offs, or processing, a little bit of that vapor is there.

What we are doing is trying to get smarter about how we do experiments to avoid some ambiguity with regard to where carbon coming from our sample comes from. And so what we did with these [rocknest] samples was we preheated the sample and let helium flow over it for something like twenty minutes and [it's] a very clear signature of all that vapor being flushed out of the system. So that's really a very robust way we believe of getting around this issue that we saw at rocknest."

Posted by: elakdawalla Mar 13 2013, 04:35 AM

I thought I heard "nanomoles," not "millimoles."

Posted by: centsworth_II Mar 13 2013, 04:57 AM

QUOTE (elakdawalla @ Mar 12 2013, 11:35 PM) *
I thought I heard "nanomoles," not "millimoles."
Right, thanks, corrected. I even had "nano" written down. wacko.gif

Posted by: Doug M. Mar 13 2013, 08:55 AM

A number of articles are mentioning the presence of nitrogen and phosphorus. I listened to the entire press conference, but I didn't hear anything about either of these two elements. Sulfates and sulfides and carbonates, but nothing about nitrogen or phosphorus. Did I miss something? And if these were found, what were the concentrations, and what compounds do they think they're coming out of?


Doug M.

Posted by: orbitmars Mar 13 2013, 09:57 AM

P2O5 has been detected in Gusev, Meridiani and Gale according to this LPSC 2013 abstract: http://www.lpi.usra.edu/meetings/lpsc2013/pdf/1653.pdf

Posted by: jmknapp Mar 13 2013, 10:35 AM

Ken Kremer from Spaceflight magazine asked about N and P:

QUOTE
Kremer: I'm interested to know, maybe even from Paul Mahaffey, about the SAM run, did you see any nitrogen, or phosphorous or chlorobutanes, and can you talk about what was the weight percent level of the phyllosilicates?

Mahaffey: I think the weigh percent of the phyllosilicates is best answered by CHEMIN, and you [looking at David Blake] gave a number for that...

Blake: 20 to 30 weight percent.

Mahaffey: ..and, did we see nitrogen compounds, we certainly are in our trace gases looking for those. It seems that we have some nitogen oxides coming up, we're looking at compounds like HCN and so on. Deconvoluting those spectra requires work and so we're working away on that, but it sure looks like we have nitrogen compounds there. In terms of phosphorous, we haven't seen any, but that really is an APXS result, they see phosphorous in their compounds. Very interestingly, we see a fair bit of hydrogen chloride coming up into our lines, and so the chlorine is not just producing these trace chloromethane compounds, but is also producing hydrochloric acid.


Just before that, John Grotzinger said this about finding CO2 in the SAM gases:

QUOTE
Grotzinger: That's what we're real excited about there, because then that gives us our sort of desiderata of key elements that are the building blocks for life: hydrogen, oxygen, phosphorous, sulfur and then of course nitrogen and then also carbon.


A mnemonic for that desiderata for life is sometimes given as CHNOPS (chi-nops).

Posted by: Doug M. Mar 13 2013, 11:45 AM

So, it looks like we're seeing P2O5 at about 0.5% to 1% by weight of various rocks, which works out to around 0.2% to 0.4% phosphorus by weight. Okay.

But OTOH, it appears that nitrogen is scarce -- a trace that they have to look hard to sort out, if it's there at all. Nitrates, nitrites, cyanides or nitriles, if present at all, must be in very low concentrations, at least in the samples taken so far. Do I have this right?


Doug M.

Posted by: Doug M. Mar 13 2013, 12:29 PM

QUOTE (jmknapp @ Mar 13 2013, 12:35 PM) *
A mnemonic for that desiderata for life is sometimes given as CHNOPS (chi-nops).


Hm, never heard that one before. Here on Earth 96%-98% of biomass is CHON. Phosphorus is the next most common, typically between 1% and 2%. Then calcium, with the exact figure a bit blurry depending on whether you count stuff like seashells as "biomass", but generally around 0.5%. (It's more like 1.5% for humans and other vertebrates, but that's because we concentrate calcium in our skeletons.) Then you have another group -- potassium, sulfur, chlorine, sodium and magnesium -- that are all between 0.5% and 0.05%; together these make up a bit less than 1% of all biomass. (They're all utterly essential, though. There's no life, not even weird extremophiles, that doesn't rely on these guys.) Sulfur is still below potassium and calcium, though. So maybe that mnemonic should be CHNOPKaCS?

After that you have a steep dropoff to the next most common element, iron, which is typically less than 0.01% of biomass. AFAIK there's no life that doesn't use iron in its chemistry, but IANA biologist and I wouldn't be shocked to find some odd microbe getting along without it. It's involved in a number of important biological processes, but it doesn't seem to be mission-critical the way that the elements listed above are. So if we're looking at the elements needed for life, they're CHON, followed by P-Ca, followed by K-S-Cl-Na-Mg and maybe Fe.


Doug M.

Posted by: NickF Mar 13 2013, 12:42 PM

Phosphorous (in the form of phosphate) is required for nucleotide biosynthesis. Iron's pretty important for redox biochemistry too; it's essential for haem (think cytochromes) and FeS cluster assembly. I'm not aware of any organisms that don't utilise it.

Posted by: jmknapp Mar 13 2013, 12:42 PM

Did he say how much N was found? Or does the fact that the N signals need to be "deconvolved" imply trace?

Posted by: Doug M. Mar 13 2013, 02:09 PM

Googling around, I found this recent paper:

http://www.lpi.usra.edu/meetings/lpsc2013/pdf/2790.pdf

-- very small amounts of HCN and nitrile.


Doug M.

Posted by: MrNatural Mar 14 2013, 02:23 AM

Would anyone care to elaborate on the SAM CO2 findings? Mahaffy noted that the CO2 peak could have been cause either by the oxidation of carbon compounds or from carbonates. I would think that either of these possibilities is rather significant.

Posted by: nprev Mar 14 2013, 03:00 AM

Not to be iconoclastic, but considering that the current Martian atmosphere is 95% CO2 (by both volume & weight, I think) the possibility of absorption by the rather soft material of the rock & subsequent re-emission seems significant as well.

Posted by: elakdawalla Mar 14 2013, 03:13 AM

I'm no GCMS expert, but as far as I understand it, any adsorbed CO2 gas would come off at a very low temperature. For it to last until several hundred degrees before being released from the sample, it has to be coming off of a mineral. If you look at p. 462 of http://link.springer.com/article/10.1007/s11214-012-9879-z, you'll see example spectra where carbonates give off their CO2 at temperatures of about 600 degrees. At least that's how I understand things. YMMV.

Posted by: nprev Mar 14 2013, 03:18 AM

Ah. Thanks! Makes sense; just thought that point should be raised for reference.

Posted by: Don1 Mar 14 2013, 04:38 AM

I think the CO2 is coming off at too high a temperature for it to be adsorbed gas.

There is quite a lot of it, and I wouldn't expect the sample to contain that much organic material. If it is combusting organics, then it could be the leaked reagent. The Rocknest sample released CO2 at a similar temperature. The Rocknest peak was broader, and that was interpeted as coming from several different sources, one of which was a decomposing Fe or Mg carbonate mineral. This release is happening at 415C, which is about the same as the biggest release from Rocknest, the origin of which is unclear.

If they measure the isotope ratios in the CO2, I think they can work out the formation temperature of the carbonate, which would give an insight into past Martian climate.

Edit: For reference, here is a paper on the CO2 release from Rocknest.
http://www.lpi.usra.edu/meetings/lpsc2013/pdf/2095.pdf
One possibility they consider is that the soil contains a lot of organic material, too much for it to be from meteors. Personally, without other evidence for large amounts of organics, I think the acid catalysed decomposition of a carbonate is a more likely explanation.

Posted by: CosmicRocker Mar 14 2013, 06:08 AM

QUOTE (Doug M. @ Mar 13 2013, 06:29 AM) *
Hm, never heard that one before. Here on Earth 96%-98% of biomass is CHON.
Very interesting. Thanks for those fascinating numbers. Might they be talking about the composition of primitive or single-celled organisms (as we know them on earth), rather than more evolved creatures able to build skeletons and such?

It is so cool to finally get this kind of chemistry from Mars. It is also beginning to sound to me as if carbonates are the more likely source of the evolved CO2. The discovery of carbonates by a rover would be pretty significant in it's own right.

Since the leaked reagent quantity is being estimated in nano-moles, it's doubtful that it could be the source of a significant CO2 signature, right?

I'll be looking forward to more news from the analytical devices on this amazingly capable rover.

Regarding the isotopic analytical abilities, is this roving laboratory able to see the individual carbon and oxygen isotopes of CO2, or must that be inferred from the masses of molecular chunks delivered to the mass spectromer?


Posted by: Doug M. Mar 14 2013, 10:12 AM

Here's a hypothetical question. Suppose you were to take a kilo or two of the rock dust from CheMin's recent sample. Pour it into a flower pot. Add some nitrogen -- say, in the form of urea crystals ground fine -- and then add a hundred grams of humus to supply soil microorganisms. Let's say we want a mix that's 95% Martian rock dust, 5% Earth humus and a bit of nitrogen.

Now add some water.

You could totally grow stuff in this, right? Plant your geraniums, or whatever? The Martian dust has potassium and phosphorus, calcium and magnesium and iron. It's got everything but nitrogen compounds, water and microorganisms. Right?

Or -- not? Are the useful elements in compounds that make them unavailable (i.e., P2O5 instead of phosphates)? Would the mechanical properties of the rock and the resulting dust (water permeability, etc.) raise issues?


Doug M.

Posted by: MrNatural Mar 14 2013, 11:50 AM

QUOTE (Don1 @ Mar 14 2013, 05:38 AM) *
I think the CO2 is coming off at too high a temperature for it to be adsorbed gas.

There is quite a lot of it, and I wouldn't expect the sample to contain that much organic material. If it is combusting organics, then it could be the leaked reagent. The Rocknest sample released CO2 at a similar temperature. The Rocknest peak was broader, and that was interpeted as coming from several different sources, one of which was a decomposing Fe or Mg carbonate mineral. This release is happening at 415C, which is about the same as the biggest release from Rocknest, the origin of which is unclear.

If they measure the isotope ratios in the CO2, I think they can work out the formation temperature of the carbonate, which would give an insight into past Martian climate.

Edit: For reference, here is a paper on the CO2 release from Rocknest.
http://www.lpi.usra.edu/meetings/lpsc2013/pdf/2095.pdf
One possibility they consider is that the soil contains a lot of organic material, too much for it to be from meteors. Personally, without other evidence for large amounts of organics, I think the acid catalysed decomposition of a carbonate is a more likely explanation.


I would think that if it is caused by combusting organics then there should be some partial combustion products produced also...

Posted by: Don1 Mar 14 2013, 08:18 PM

QUOTE (CosmicRocker @ Mar 13 2013, 11:08 PM) *
Since the leaked reagent quantity is being estimated in nano-moles, it's doubtful that it could be the source of a significant CO2 signature, right?
.
.
Regarding the isotopic analytical abilities, is this roving laboratory able to see the individual carbon and oxygen isotopes of CO2, or must that be inferred from the masses of molecular chunks delivered to the mass spectromer?


In the paper I linked, they definitely claim that the estimated size of the leak is far too small to account for the amount of CO2 produced. There is also too much CO2 for meteoritic organics to be the source.

The best instrument for isotopic studies of H2O, CO2 and CH4 is the tunable laser spectrometer, which is a part of SAM. This uses light absorbtion in a gas cell to measure isotope ratios. All the individual C, H and O isotopes can be measured. TLS only samples a fraction of the gas evolved on each run, so at Rocknest they did multiple SAM runs to get full coverage.

@MrNatural : When organics burn they often produce partial combustion products like carbon monoxide, and I haven't seen any mention of that.

Posted by: serpens Mar 14 2013, 10:30 PM

QUOTE (CosmicRocker @ Mar 14 2013, 07:08 AM) *
It is so cool to finally get this kind of chemistry from Mars. It is also beginning to sound to me as if carbonates are the more likely source of the evolved CO2. The discovery of carbonates by a rover would be pretty significant in it's own right.


Already been done. Spirit at Comanche.

Posted by: CosmicRocker Mar 14 2013, 11:29 PM

Oops, I forgot about Comanche.

Posted by: dvandorn Mar 15 2013, 12:17 AM

Phoenix also identified carbonates as one of the constituents of the soil at its landing site. Only something like two or three percent, IIRC, but definitely there and detectable.

Of course, when you have a CO2 atmosphere, I imagine there are a heck of a lot of ways to make carbonates.

-the other Doug

Posted by: serpens Mar 15 2013, 05:43 AM

Not without non-acidic water.

Posted by: Don1 Mar 15 2013, 08:09 PM

Small amounts of carbonates were detected in the soil at Rocknest. Siderite (Fe carbonate) was found at an abundance of 0.8% wt, and magnesite (Mg carbonate) is suspected. Isotopic studies indicate that they formed at 0C or below, and the theory is that the minor amount of carbonates in martian soil could have been derived through atmosphere interaction with soil with only transient water.

http://www.lpi.usra.edu/meetings/lpsc2013/pdf/2066.pdf

Posted by: pospa Apr 8 2013, 02:27 PM

Atmospheric measurements done by SAM revealed much higher amount of heavier isotop Ar38 then lighter Ar36.
Mars has lost around 85% to 95% of its atmosphere over the course of billions of years.

http://www.planetary.org/blogs/casey-dreier/2013/20130408-curiosity-detects-atmospheric-loss.html

Posted by: Gerald Apr 8 2013, 03:57 PM

(Moved from thread "First drill stop: John Klein in Yellowknife Bay")
http://streams.h82.eu/EGU2013/index.php?modid=18&a=show&pid=204

http://www.egu2013.eu/webstreaming.html

Posted by: Don1 Apr 14 2013, 09:38 PM

The SAM results from EGU show significant differences to the previous ones. There are now 2 oxygen peaks rather than 1, and suggestions of a second oxidant, possibly hydrogen peroxide. The temperature of the CO2 release seems to have dropped, and it coincides with a dip in the O2. The team speculated that some carbon containing substance is being combusted by the O2 to produce CO2. There are also other possibilities.

The new results are from the same sample as the first ones were, so I don't know why the results are different. Maybe the heating was done differently. If combustion is the source of the CO2, then there is a lot of organic present, maybe 1% abundance.

Posted by: marsophile Apr 15 2013, 03:42 PM

QUOTE (Don1 @ Apr 14 2013, 02:38 PM) *
... same sample ... the results are different.


I recall reading that the size of the analyzed portion this time is about 3 times the size of the previous portion. This might mean that the effect of remnant Rocknest material is less?

Posted by: elakdawalla Apr 15 2013, 05:46 PM

Could the runs have used different GC columns?

Posted by: t_d Apr 16 2013, 11:36 AM

QUOTE (Don1 @ Apr 14 2013, 05:38 PM) *
The SAM results from EGU show significant differences to the previous ones. There are now 2 oxygen peaks rather than 1, and suggestions of a second oxidant, possibly hydrogen peroxide. The temperature of the CO2 release seems to have dropped, and it coincides with a dip in the O2. The team speculated that some carbon containing substance is being combusted by the O2 to produce CO2. There are also other possibilities.

The new results are from the same sample as the first ones were, so I don't know why the results are different. Maybe the heating was done differently. If combustion is the source of the CO2, then there is a lot of organic present, maybe 1% abundance.

Wow. That's a lot of organics! How could this be confirmed?

Posted by: MahFL Apr 16 2013, 11:38 AM

They did say they are no where near having ran all the scripts they can on Sam and Chemin, so new findings should be expected as time goes by and they gain more experience with the equipment in situ.

Posted by: Don1 Apr 16 2013, 09:10 PM

@marsophile & Emily : I've no idea why the runs are giving different results. The team didn't comment on this, so maybe there is a trivial explanation. The graph of the April results is http://mars.jpl.nasa.gov/msl/multimedia/images/?ImageID=5200&NewsInfo=59C884BFF2B8E0EFCDD902B94F94BA55AC4A8F9603007ADCCA4F50EBACD6D68CDF99D8DCE3D1DF46C65D9FEBC2EF920BCACFD306DA4114E8DB1FCBCF0365D73902CDE74CC312C9CDD70F13D2C8D527C7B6C7ABFEC5EFD1DED3C882C4150D4A15DF4BD29B4A412F67C93F8FD5C842EABD4EB90E5356805C and the March results are http://mars.jpl.nasa.gov/msl/multimedia/images/?ImageID=5125&NewsInfo=59C884BFF2B8E0EFCDDC0BB94F94BA55AC4A8F9603007ADCC24950FEA8D6DE97C781DED8F6DCC257CA4093E3DCFF8B0CCBCDCE0ADA4216EBDB0ACFCF007BCE2805CBFB4ADE00C9D3D20A0DC4DBA97684A789FBBB86

The most obvious difference is the relative position of the CO2 and O2 peaks.

@t_d : There are several capabilities of SAM that have yet to be used. It can supply oxygen to the sample to combust any organics that are present, and can then measure the isotope ratios of the produced CO2. It can also do a wet chemistry experiment which should be able to remove the perchlorate which would make it possible to detect the structure of any organic molecules present.

Posted by: stone Apr 17 2013, 06:39 AM

The March results start at 480F (248°C) while the 4th John Klein Sample starts at "room temperature". The first sample was preheted to 250°C to get rid of the MTBSTFA contamination observed in the Rocknest samples. This was not done at the lats John Klein.

The first oxygen peak of JK1-3 is therefore not present in the JK4 measurement because it is at 220°C.




Posted by: serpens Apr 17 2013, 07:23 AM

One scale Fahrenheit and the other Celcius? I would have thought that based on past experience metric/centigrade would have been compulsory for anything connected to the space program but at least they could be consistent.

I can appreciate the desire to burn off contamination in the first run, but that doesn’t explain why the O2 and CO2 peaks are transposed between the two plots. As Don1 stated the relationship between CO2 and O2 plots for the 4th JK plot does imply some kind of combustion but the CO2 maxima is above the 250 Celcius preheat temperature and it is hard to fathom why artefacts above that temperature should be so dramatically different.

Posted by: Don1 Apr 17 2013, 07:54 AM

@stone: That doesn't explain why the temperature of the CO2 peak has changed. It was 415C in the March data and has moved down to a little under 300C in the 4th John Klein sample.

@serpens: It's the usual story, the US using Fahrenheit and the Europeans using Celsius. The next plot will probably be in Kelvin. wink.gif

Posted by: AndyG Apr 17 2013, 08:15 AM

QUOTE (Don1 @ Apr 17 2013, 07:54 AM) *
The next plot will probably be in Kelvin. wink.gif


Rømer degrees would be more appropriate smile.gif (scale based on the freezing point of brine).

Andy

Posted by: stone Apr 17 2013, 08:24 AM

The GC is French so the next one is in Réaumur. At the higher temperatures the only temperature I would use is Wedgwood.



Posted by: serpens Apr 17 2013, 12:08 PM

Wedgewood. Groan. Say, that transposition between CO2 and O2 peaks couldn't be a finger error in labelling plots could it?

Posted by: elakdawalla Apr 17 2013, 12:28 PM

Just to be clear, the US scientists are using Celsius or Kelvin. Fahreheit only shows up in figures made for press briefings. Which are unfortunately the only images that routinely make it on to the Web. Nice that at least in Europe the press-released images and press conferences are conducted in the same units that the scientists think in, at least professionally.

Posted by: stone Apr 17 2013, 12:50 PM

QUOTE (serpens @ Apr 17 2013, 02:08 PM) *
CO2 and O2 peaks couldn't be a finger error in labelling plots could it?


The dent in the O2 peak when the CO2 is released seam reasonable.

The amount of CO2 and O2 is not really deducible from the plots. It gives only the MS detector count numbers. The ionization ratio is very different for the small molecules. A little bit of oxygen can give you a large peak while the same amount (number) of CO2 gives you a weak signal. I have no clue about the ionization ratio of both species.

Posted by: serpens Apr 18 2013, 01:09 AM

Yeah the 4th sample looks kosher. I was thinking along the lines of an error in labelling in the first plot identified by Emily as a press release image.

Posted by: Gerald Apr 28 2013, 03:06 PM

QUOTE (Don1 @ Apr 14 2013, 11:38 PM) *
The SAM results from EGU show significant differences to the previous ones. ...
The new results are from the same sample as the first ones were, so I don't know why the results are different. Maybe the heating was done differently.

On EGU 2013, Monday, 08 April 2013, Press Conference 1, "Latest results from the Curiosity Mars Rover", John Grotzinger told:
QUOTE
... and John Klein 4 gave us a different run where we changed the ramp, the temperature process by which the sample is run ...

see http://streams.h82.eu/EGU2013/index.php?modid=18&a=show&pid=202, 03:50-04:00.

Posted by: Don1 Nov 14 2013, 08:55 PM

Here are some quotes from AGU 2013 abstracts on SAM:

Re organic compounds detected by SAM
"[Mars samples] afforded a number of chlorohydrocarbons including chloromethane, dichloromethane, trichloromethane, a chloromethylpropene, and chlorobenzene (1, 2). Some proportion of these compounds can be traced to instrument background from organic materials within the chromatographic columns, hydrocarbon traps and wet chemistry capability of SAM... (MTBSTFA) and dimethylformamide, compounds carried in SAM for chemical derivatization can react with gases released from the sediments to yield the C1 and C4 chlorohydrocarbons. However, we continue to explore the possibility that a portion of the C1 chlorohydrocarbons are derived from organic carbon compounds on Mars."

For completeness, here is a link to Emily's October 15th blog post concerning the SAM results presented at DPS 2013:
http://www.planetary.org/blogs/emily-lakdawalla/2013/10151336-dps-2013-confusing-curiosity.html

My opinion is that SAM's organic detection capability is broken and probably won't get fixed unless the rover gets away from the perchlorates. All the organics being detected can be explained as the product of leaking MTBSTFA reagent reacting with Martian perchlorates. There seems to be little hope of a robust, convincing result on the Yellowknife Bay samples.

There is also this. Prior to launch the derivatization capability of the wet chemistry cells was touted as providing the solution to the problem of detecting organics in environments that contained perchlorate. However, the following abstract hints at a possible problem with samples that contain hydrated minerals:
"To enable a more accurate interpretation of the in situ derivatization GC-MS results that will be obtained by SAM, the lab experiments were performed as close as possible to the SAM flight instrument experimental conditions. Our first derivatization experiments display promising results, the laboratory system permitting an extraction and detection of several proteinogenic amino acids and carboxylic acids from Martian analog materials. Preliminary results show a lack of derivatized organic molecules in hydrated solid samples however, where the MTBSTFA reagent possibly reacts preferentially with the water from hydrated minerals (Stalport et al. 2012)."

Stalport et al. 2012 is online http://science.gsfc.nasa.gov/691/analytical/PDF/Stalportetal2012.pdf From the abstract "... However, the rapid reaction of MTBSTFA with water in several analog materials that contained high abundances of hydrated minerals, and the possible deactivation of derivatized compounds by iron oxides,...proved to be highly problematic for the direct extraction of organics using MTBSTFA".

For years, scientists have been talking about searching for Martian clays and the hope that they would offer a good environment for preserving organic compounds. If the wet chemistry capability on SAM doesn't work with clay minerals, then why wasn't that discovered a long time ago?

Posted by: stone Nov 18 2013, 09:11 PM

QUOTE (Don1 @ Nov 14 2013, 09:55 PM) *
For years, scientists have been talking about searching for Martian clays and the hope that they would offer a good environment for preserving organic compounds. If the wet chemistry capability on SAM doesn't work with clay minerals, then why wasn't that discovered a long time ago?


The wet chemistry was never intended to be of any use for trace levels of organics. Only 7 ovens are with derivatisation and the rest of ca 60 are only pyrolyis. Derrivatization is the silver bullet for amino acids. A. Buch should have some publications on that topic. If you have a normal Mars sample with trace levels you would never use one of the derivatization capsules. The pyrolysis is not a best method, but the best what you ever brought to Mars. The method will be used until pyrolysis would show you elevated levels of organics with some nitriles and some nitrogen compounds you know are amino acid derivates. The same sample would be filled into a derivatization oven and heated to 250°C to make a reaction. Then the whole stuff will be trapped in the hydrocarbon trap and then through the chiral column of the GC. With the MS to detect you can seperate most of the amino acids into ther enantiomeres and with a little luck you have an ee (enantiomeric excess). Case proven! Life on Mars.

This is the story I wait for.

The GC-MS onboard the Exomars rover for the 2018 launch still includes derivatization capsules, after the disturbing news from SAM.

MSL09 was developed in the time before the perchlorate was discovered in 2008. The way NASA is managing instruments, a strong change in the instrument was no longer possible at that time. So they had to life with the derivatization they had at that time. Not really true because they implemented the TMAH, which was nor baslined at that point. The clay minerals are a problem anyway. They are like a sandwich with the good stuff between the two layers, but it is hard to get the good stuff out from there. Some studies by P. Ehrenfreund showed that extraction techniques give bad yields and from my experience with pyrolysis of clay samples it is the same. Clays are a good thing to have because they preserve the organics in the layers, but they also hide them in a way.

Here on earth nearly nobody uses derivatization directly on soil. There are some strange humic acid researchers doing derivatization, but they try to dry the sample well and they need a lot of time to get things right. Here on earth you do extraction with acid and solvent and do the derivatization without the disturbing, interfering and reacting inorganic material. The SAM team did inovative and good things, but they were hit by this leak in one of the derivatization capsules.

Posted by: Don1 Dec 11 2013, 11:57 PM

The latest SAM results are complicated, so I'll just comment on the CO2 releases and the chances for organics.

The team makes a good case that the carbon in the CO2 comes from a Martian source. There is 50 times more CO2 than can be explained by combustion of the leaking reagents MTBSTFA/DMF. One possibility is that hydrochloric acid released from decomposing perchlorates is catalysing the decomposition of a Martian carbonate. The other possibility is that oxygen released from decomposing perchlorates is combusting a Martian organic.

If the CO2 is coming from an organic then there is a lot of organic here, maybe in the parts per thousand range. SAM can detect organics at an abundance as little as 1 part per billion (ppb), and organics have been detected in Martian meteorites at an abundance of 100 ppb.

The only organic molecules directly detected by SAM are some simple chlorinated hydrocarbons. The abundance of these declines when special measures are taken to drive the leaking reagents MTBSTFA/DMF out of the system.

When organic minerals like coal combust on earth, they typically produce a range of pollutants like nitrogen and sulfur oxides and unburned hydrocarbons in addition to CO2 and water. Both nitric and sulfur oxides are detected by SAM, but no organics other than chlorinated hydrocarbons are being seen.

The team seems to think that any martian organics are likely to be heavily degraded by the combination of radiation and perchlorates. The hope for the future seems to be on finding an environment that is better for preservation.

Posted by: marsophile Dec 12 2013, 02:31 AM

This is probably naive, but is there some way to trap the hydrochloric acid and then add it to an unheated sample? That might serve to identify carbonate if it is there.

Posted by: Don1 Dec 12 2013, 08:20 PM

I think there is a cold trap in the instrument which is used for concentrating organics, but there is no way to put anything back into the sample chamber.

Posted by: stone Dec 12 2013, 08:37 PM

The trap is filled with Tenax an organic material which is a good sorbent for organic material at low temperatures. HCl is not the best material for being adsorbed there. The tubing schematic is complicated I have too look it up again, but reintroducing material was never planed.

The total absence of any non-chlorinated hydrocarbons gives the impression that the overall principle of pyrolysis-GC-MS might be not the proper way to do the search for organics on mars. I feel very sorry for the SAM team that the perchlorates seem to be everywhere.


Posted by: Gerald Dec 12 2013, 09:03 PM

There is also a noble gas trap. But my knowledge is too limited to decide, whether they can/should be used (by skipping the scrubber) to trap HCl gas or liquid hydrochloric acid. Traps can be heated to release the contents. It's at least an interesting idea.
http://www.planetary.org/blogs/emily-lakdawalla/2012/curiosity-instrument-sam.html will be a good introduction to SAM.

Posted by: stone Dec 12 2013, 09:46 PM

The fragile 1/16th tubing and the valves are not made to withstand HCl for several years at elevated temperatures needed for the gas flow. I hope they do not get any corrosion.

Posted by: Don1 Dec 12 2013, 09:55 PM

The perchlorate distribution may be patchy. John Klein and Cumberland were drilled in the same type of rock and they are only 3m apart. And yet the O2 abundance at Cumberland was nearly 8 times greater than at John Klein. There are other differences as well. The John Klein release had 2 peaks, and it started at lower temperatures than Cumberland, so there may be another oxygen source besides perchlorate.

Whatever is releasing the oxygen is not evenly distributed, so I'm hopeful that at some point the rover will get away from it.

http://www.sciencemag.org/content/early/2013/12/05/science.1245267.full.pdf?keytype=ref&siteid=sci&ijkey=A8DWsMuw8ZWVY

Posted by: stone Dec 13 2013, 07:15 AM

The perchlorates are very water soluble. So lets assume that they are there for billions of years. The water amount varies due to the change in obliquity. Additionally the rocks at the surface are weted and dried every day. With this cycle the perchlorate moves by Capillary effects. If the perchlorates are concentrated at the surface of the rock, because the internal salt concentration forces the perchlorate to the outside, the wind will erode the material away and you have a rock with low perchlorate concentration. If the rock is more like an ion exchanger and likes the perchlorate ions inside the concentration in that rock type might be high.

The problem is always that you need to find a juice rock with low perchlorate concentration. A juice rock with high perchlorate concentrations will give you CO2 and other unspecific molecules.

The worst thing for me is that the most interesting molecules are the ones which are oxidized much faster than the aromatic compounds. C-N bonds and C-O bonds weaken the structure for oxidation. So a sugar with C6H12O6 compared to cyclohexane C6H12 and benzene C6H6 will be the first molecule to end up as CO2. But this molecule would indicate a biochemistry while the other molecules do only indicate that there is organic material present.

Posted by: Gerald Dec 13 2013, 12:44 PM

So far I've only fringe ideas to overcome that obstacle, meaning to synthesize the necessary reagents like water or HCl from Martian soil. That's either extraordinarily difficult or not possible with SAM.
If it's possible to synthesize some water by dry destillation of a "large" sample or by accumulating some water by repeated experiments, and this water could be delivered back to a small sample, one could try to leach out perchlorates together with polar organic compouds. By heating, polar and non-polar compounds should burn up / evaporate in a different way from an untreated sample, showing the presence of polar organic compounds.
But I actually doubt, that this can be performed. Mainly because I suspect, that transporting trapped substances back to the ovens isn't foreseen.
Next question: Can ovens be kept under pressure to enable water to condense?

So, at the end, I think, they'll try a wet cup, if there is sufficient evidence for the presence of organics.

Posted by: stone Dec 13 2013, 07:12 PM

To get enough water for leaching seems unlikely.

There was a good idea and already some hardware development for the Urey instrument.
Subcritical water extraction followed by a sublimation step to get ride of the salts. (pre Phoenix so no perclorates)

http://www.geology.wisc.edu/astrobiology/docs/Bada_et_al_2008_Space_Sci_Rev.pdf
----Urey: Mars Organic and Oxidant Detector
http://astrobiology.berkeley.edu/PDFs_articles/08UreyAstrobio.pdf
---The Urey Instrument: An Advanced In Situ Organic and Oxidant Detector for Mars Exploration

The instrument was a good idea and would have been a good start for sample preparatuion. The Micro-Capillary Electrophoresis is not the best method I can think of but the extraction would benefit any Mars mission.

If you have another brilliant idea the MOMA pyrolysis GC-MS team is always searching for the perfect method to get rid of the perchlorates.

Posted by: Gerald Dec 14 2013, 01:38 AM

QUOTE (stone @ Dec 13 2013, 08:12 PM) *
If you have another brilliant idea the MOMA pyrolysis GC-MS team is always searching for the perfect method to get rid of the perchlorates.

Ok, a try out of the hip:
QUOTE (stone @ Dec 13 2013, 08:15 AM) *
C-N bonds and C-O bonds weaken the structure for oxidation. So a sugar with C6H12O6 compared to cyclohexane C6H12 and benzene C6H6 will be the first molecule to end up as CO2.

If this logic holds, why not "flood" a powdered rock sample with a known substance which is much more easily oxidizable? That way you get the perchlorates/chlorates reduced with a much smaller proportion of the "interesting" compounds being oxidized/destroyed.
The remainder of the substance including decay products should obviously be subtracted from the measured data.
Not yet perfect, but may be an improvement, technically not too difficult.
Two experiments with different reducing substances should reduce uncertainties about reaction products with these substances.
If all else fails, C-13, O-18, D-compounds could be used to later distinguish decay products.

Posted by: marsophile Dec 14 2013, 03:13 AM

The diagram in Emily's blog indicates that waste products from SAM are vented.

Does anyone know where the vent is located? Is it reachable by the rover scoop? If, say, water vapor were to be vented at night, it would presumably condense into frost and might be collected on top of a sample, perhaps?

Posted by: stone Dec 14 2013, 12:21 PM

QUOTE (Gerald @ Dec 14 2013, 02:38 AM) *
Ok, a try out of the hip:

If this logic holds, why not "flood" a powdered rock sample with a known substance which is much more easily oxidizable? That way you get the perchlorates/chlorates reduced with a much smaller proportion of the "interesting" compounds being oxidized/destroyed.
The remainder of the substance including decay products should obviously be subtracted from the measured data.
Not yet perfect, but may be an improvement, technically not too difficult.
Two experiments with different reducing substances should reduce uncertainties about reaction products with these substances.
If all else fails, C-13, O-18, D-compounds could be used to later distinguish decay products.


Formic acid, Hydrogen CO or paraformaldehyde in a small capsule in the oven were my first coice for that, and after the problems with SAM isotopically enriched material for the derivatization reagents was our plan.

It will take a few months to test all the possibilities to get a final decission.


Posted by: Gerald Dec 14 2013, 12:34 PM

QUOTE (marsophile @ Dec 14 2013, 04:13 AM) *
The diagram in Emily's blog indicates that waste products from SAM are vented.

Does anyone know where the vent is located? Is it reachable by the rover scoop? If, say, water vapor were to be vented at night, it would presumably condense into frost and might be collected on top of a sample, perhaps?

That's at least an idea for a round-trip, but...

There is a hint in http://link.springer.com/article/10.1007/s11214-012-9879-z, p. 433, where the exhaust vent goes:
QUOTE
The molecular drag stage is designed to exhaust directly to the Mars ambient surface pressure of 700 to 960 Pa.

I'd think, that even if water vapor would be exhausted at night, it would be dispersed finely, especially regarding the slope winds at night, and sublimate soon after sunrise. No way to get significant amounts scooped.

Posted by: stone Dec 14 2013, 03:09 PM

The operating of the drill so close to the exhaust would never be allowed. The NASA mission planing is a very conservative.

The amount of water you need to get it through the sample preparation and from there into an oven would be very difficoult with small amount.

Posted by: Don1 Dec 14 2013, 09:52 PM

The sample size is around 100mg so only 2mg of water would be produced. I don't think that would be feasible to collect.

The only thing that will work for MSL is a sampling strategy that collects organics while avoiding perchlorate. Since the perchlorate is falling out of the sky, a recently exposed surface at the base of a scarp may have less perchlorate than elsewhere. Another possibility would be to drill into the base of a cliff where an impermeable cap shields lower layers from perchlorate contamination. They'll just have to try different things, which is going to take time.

Another issue here is that the perchlorate is part of a bigger picture that may involve other oxidants. The oxygen from John Klein and Cumberland is being released at a lower temperature than at Rocknest, and the temperature of the release doesn't match that of common perchlorate salts. The presence of iron oxides may lower the decomposition temperature of perchlorate salts, or we may be dealing with a chlorate rather than a perchlorate.

For those who aren't familiar with chemistry, there is a family of these oxy-chlorine ions. Perchlorate has one chlorine bonded to 4 oxygens, while chlorate has one chlorine bonded to three oxygens. There is also chlorite with 2 oxygens, and hypochlorite with one oxygen. Household bleach is sodium hypochlorite solution.

For future reference here are links to charts showing SAM results from http://photojournal.jpl.nasa.gov/jpeg/PIA17599.jpg, http://photojournal.jpl.nasa.gov/jpeg/PIA16817.jpg, http://photojournal.jpl.nasa.gov/jpeg/PIA16835.jpg and http://photojournal.jpl.nasa.gov/jpeg/PIA16575.jpg.

Posted by: Gerald Dec 15 2013, 06:48 PM

QUOTE (Don1 @ Dec 14 2013, 10:52 PM) *
The sample size is around 100mg so only 2mg of water would be produced. I don't think that would be feasible to collect.

The cups aren't restricted to one sample (I don't know the upper limit). So heat e.g. 10 samples at once (1g) to get 20mg of water. (On Earth http://en.wikipedia.org/wiki/Drop_(unit) is about 60mg.)
We're certainly dealing with a cocktail of several chlorine-bearing salts, and trapped oxygen, as perchlorates are decomposed via http://en.wikipedia.org/wiki/Radiolysis, see e.g. http://www.lpi.usra.edu/meetings/lpsc2011/pdf/2003.pdf.

Techniques applicable to a sample to separate anorganic salts from organics, if water could be delivered to a cup, and if other methods fail:
- rudimentary http://en.wikipedia.org/wiki/Fractional_crystallization_(chemistry) on a microscopic scale,
- using previously heated samples as kind of http://en.wikipedia.org/wiki/Column_chromatography (stationary phase) with water as mobile phase. (More intuitive images http://en.wikipedia.org/wiki/Thin_layer_chromatography.) (Inspired by the electrophoresis idea of the Urey instrument.)

(Separation of organics from oxidizing salts would make them more likely to be detected.)


Posted by: stone Dec 15 2013, 10:05 PM

There are several methods already developed.
*Alkohol extraction and than giving it through a cartridge filled with a unpolar substituted adsorbent and than wash it with hexane. (reversed phase solid phase extraction)
*HPLC is a method already very capable to work without the need to separate from most salts.

This all has a liquid extraction step and needs a lot of technical knowledge with no flight heritage. It will cost 80 million or more to develop. It will be 15kg+.

I would like to go for that but neither ExoMars nor 2020 will do such a thing.

Posted by: Gerald Dec 16 2013, 12:49 PM

Operating with available MSL SAM payload:

http://link.springer.com/article/10.1007%2Fs11214-012-9879-z/fulltext.html#Sec30:

QUOTE
Valve/Heater (VH) Module: The VH module provides a 7 amp forward or reverse drive pulse to any one of the 52 micro valves as well as regulated switched power to 60 heaters (9 at 28 V and 51 at 10 V) under the control of the CDH. It also generates the AC drive sweep for the SSIT shakers.

Knowing this and based on http://link.springer.com/article/10.1007%2Fs11214-012-9879-z/fulltext.html#Sec1 , Figure 3, here a sketch, how interaction of water vapor with a sample could work:
- Deliver H2O-bearing large (e.g. 1g) sample(s) (sample 2) via SSIT 2 to an inner quartz cup (cup 2).
- Deliver small sample (e.g. 100mg) via SSIT 1 (sample 1) to an outer quartz cup (cup 1).
- Heat cup 2 in Oven-2, valves V32 (Oven-2) and V37 (H2O Scrubber?) forward to collect H2O from sample 2.
- Close V32 and V37.
- Put cup 1 into Oven-1 without heating.
- Heat H2O scrubber with valves V37 (H2O Scrubber?) and V30 (Oven-1) reverse to release H2O to sample 1.
- Close V30 and V37.
- Wait for H2O vapor acting on sample 1.
- Heat Oven-1, with V30 forward and subsequent analysis settings (SS-EGA/GCMS).

With some luck a similar workflow could also work for HCl being trapped. Combining HCl with an excess of water vapor could reveal (non-metamorphic) carbonates.

Posted by: Don1 Dec 16 2013, 09:25 PM

I'm not quite sure what we are talking about here. I think that everybody agrees that for a future mission there are possible ways to handle the perchlorate problem.

If we are talking about the SAM instrument currently on Mars then it may be possible to make it do things for which it was never designed however you are likely to run into all kinds of challenges. I think there is a way to flow oxygen from a reservoir into the oven and then send the products to the detectors. Looking at Figure 3 referenced above it might be possible to flow gases from the "H20 and CO2 scrubber" along a similar path. And the absorbers used for scrubbing CO2 usually work for other acidic gases, so it is likely that they would trap HCl. So I think there is a chance that Gerald's scheme for detecting carbonates might work, however I don't know enough about SAM to be sure.

Before we think about teaching SAM new tricks I think we should remember that there are a number of tricks that SAM was supposed to know which we have yet to see performed. For instance SAM hasn't done the O2 combustion experiment or the wet chem experiments or the methane concentration experiment. There seems to be some kind of hold up with writing software or ground testing.

Posted by: stone Dec 16 2013, 10:25 PM

There ar really feasible ways to deal with the oxychloroanions? There is a lot of hypothesis out there but this is paper work not real instruments or proven concepts. Nothing will be on the 2020 rover or ExoMars which is that suffisticated and new. Beyond this there might be a solution, but this rover or platform is yet to be named or anounced.

Posted by: nprev Dec 16 2013, 10:55 PM

Don1, I think it's more likely that the science team is trying to positively ascertain the results thus far & determine the best course of action before doing something unusual--and possibly risky---to the SAM's functional parameters. I don't see this as being something done lightly.

Posted by: stone Dec 17 2013, 07:23 AM

The AGU talk and a JGR paper show clearly that the machinery at Goddard and the MIT is trying very hard to get the SAM parameters right. SAM is little more complex than other instruments and upto now the SAM team used not all possible columns and did not use all traps they have and they have still the derivatization reagents onboard. So a lot of possibilities to do before to go for the "never thought of" option. But it still fun to talk about the options they have. The Curiosity mission is not very likely to allow anything which is not in the written specs of the mission. The ground model of SAM at Goddard is in use all the time to verify the operations done on Mars and only if the strange things would work at that machine it would be a possibility for mars.

The Aeolis mons is still their target and only if they find nothing suitable and perchlorate free there they will go for something strange.

The 2020 Rover payload will be fixed soon and there a perchlorate resistant method would be very nice, but I doubt that the mission would allow a instrument without flight heritage and low technical readiness level.

For ExoMars the thing is nearly over. The Laserdesorption of the MOMA instrument is capable to find organics in the presence of perchlorates and the RAMAN is also possible to do without being influenced. So lets hope for ExoMars.

Posted by: Gerald Dec 17 2013, 10:21 AM

I'd think "in due time" they'll try to synthesize a droplet of liquid water from Martian soil as a proof of concept, and because it will probably be regarded as a symbolic milestone. I'm sure it's already on a long list of proposals.
Many of the risks of a BASIC script run on SAM can be assessed by software simulation (http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20130014439_2013014290.pdf) without risking damage to hardware, be it test bed or Mars.
Possible bottlenecks (e.g. Scrubbers) in a destillation process can be overcome by repeated destillation of soil to the same "condensation cup".

Such an experiment will be rather time and power consuming, and if they follow a shortest-job-first strategy, it may be done in an extended mission.

Posted by: Harder Dec 17 2013, 12:00 PM

It would be interesting to learn about Goddard’s SAM model’s technical longevity - being in continuous use and possibly trying out new sequences as discussed here.

Stone mentioned earlier that the tubing and valves may not be suitable for prolonged exposure to HCl. From what I’ve seen in corrosion attacks in oil refinery equipment, dry gaseous HCl is no problem per se, but at the location where the first drop of water condenses (in the presence of gaseous HCl) you get a concentrated acid attack that also goes thru Stainless Steel. Think of the original Alien movie.

From what I’ve learned in Emily’s blog, SAM is about manipulating and analyzing gaseous streams but some scenario's brainstormed by Gerald aim to “introduce” water….

Posted by: Gerald Dec 17 2013, 12:58 PM

That's a good point!

So this is only allowed to happen within a quartz cup.
The challenge is then the appropriate heating of the tubes (made of nickel).
Similar precautions have to be taken during "designed" sample analyses.

Posted by: Don1 Dec 18 2013, 03:27 AM

I'm not very keen on any scenario which accumulates hydrochloric acid inside SAM. The samples are small and wouldn't produce much, but we need this instrument to last a long time.

For a future mission, I assume that a Raman spectrometer would be able to detect organics even in the presence of perchlorate. That is a totally different instrument from SAM, and doesn't depend on heating anything. I believe it gives a lot less information on the types of organic compounds present than SAM, but as a touch science instrument it would be much quicker to use.

Posted by: Gerald Dec 18 2013, 12:06 PM

Thinking about how to design SAM experiments helps to better appreciate the job the SAM team is doing day by day. I can only leave the cost/benefit assessments and decisions to them.

The Raman approach (http://www.lpi.usra.edu/meetings/marsconcepts2012/pdf/4188.pdf) has been proposed for the 2020 mission, see http://mars.jpl.nasa.gov/mars2020/files/m2020/SDT_Appendices_Final_v6.pdf, p.169.

Posted by: marsophile Dec 18 2013, 09:12 PM

A couple more questions about potential instrument interactions.

If SAM could add water (not HCL) to a solid sample, would this possibly encourage the growth of additional crystals from the amorphous component that might be detected by CHEMIN?

After a pyrolyzed solid sample from SAM has been dumped, would it be feasible or useful to do an APXS analysis of the residue?

Posted by: Gerald Dec 18 2013, 09:56 PM

I've been thinking at the same idea. H2O could turn some amorphous phases to crystals, or enrich minerals.
But unfortunately SAM samples cannot be dumped, but remain in the cups "forever". Only gas can be released to the environment (probably).
Would be nice to get the contents of cups somehow to CheMin or APXS. I'm not aware of such an option.

Posted by: Gerald Mar 3 2014, 10:44 PM

QUOTE (Don1 @ Dec 16 2013, 10:25 PM) *
Before we think about teaching SAM new tricks I think we should remember that there are a number of tricks that SAM was supposed to know which we have yet to see performed. For instance SAM hasn't done the O2 combustion experiment ...

http://astrogeology.usgs.gov/news/astrogeology/sol-557-559-update-on-curiosity-from-usgs-scientist-ken-herkenhoff-discipline:
QUOTE
... the SAM instrument has been doing overnight combustion experiments that require lots of power. The last one of these is planned early in the morning of Sol 558...

Now I'm curious, whether these experiments allowed to distinguish between carbonates and organics. If more CO2 has been released at lower temperatures at an excess of O2, this could indicate the presence of organic compounds.

Posted by: vikingmars Mar 28 2014, 09:00 AM

wheel.gif wheel.gif wheel.gif wheel.gif wheel.gif
Thanks so much Emily about the nice article found this morning in "Science" magazine ("Search for @@@@ Clears Another Hurdle") you "co-authored" with Richard Kerr and which summarizes very well the latest discoveries made by SAM about organic compounds.
Dixit :
"Caroline Freissinet and Daniel Glavin of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and a score of fellow SAM team members reported that the latest results are persuasive. The new findings offer “compelling” evidence that some of the carbon-containing compounds SAM recently detected such as chlorinated methane, ethane, and propane came from organic matter in ancient martian rock, not from earthly contamination, Freissinet said. And Glavin said that other results are “a good indication” that some of the chlorobenzene is martian as well. Or as one of his slides pointedly put it: “The detection of reduced organic compounds in Martian near-surface samples is a signifi cant step.”
The implications for "@@@@" are interesting and because this is a forbidden topic on this Forum, I hope that you will give us more insights inside your nice blog in the TPS website... wink.gif


Thanks so much in advance Emily !
VM (also supporting your much-appreciated work as Charter Member of TPS)

Posted by: serpens Mar 29 2014, 11:18 PM

More than a touch of overkill there I think. The possible detection of organic material by SAM has nothing to do with astrobiology and the lack of accumulated organic material from infall has always been a bit of a head scratcher. To segregate from discussion elements of the SAM results which could have a significant effect on the interpretation of the depositional environment seems a little silly. I think forum members are well aware that organics simply refers to material containing carbon and hydrogen atoms and the moderators responsibility is to ensure that posts don't drift off topic. Just my five cents worth.

Posted by: diane Mar 30 2014, 03:49 PM

QUOTE (serpens @ Mar 29 2014, 06:18 PM) *
More than a touch of overkill there I think. The possible detection of organic material by SAM has nothing to do with astrobiology and the lack of accumulated organic material from infall has always been a bit of a head scratcher. To segregate from discussion elements of the SAM results which could have a significant effect on the interpretation of the depositional environment seems a little silly.

Agreed. Organic chemistry is the chemistry of carbon. Biochemistry is the chemistry of things that crawl. As I understand it, Curiosity doesn't have sufficient instrumentation to cross that line. As long as we stay on chemistry, we should be fine.

Posted by: elakdawalla Mar 30 2014, 04:07 PM

In his talk Glavin repeatedly referred to http://adsabs.harvard.edu/abs/2000PNAS...97.2425B, and that benzenecarboxylates were a possible precursor to the chlorobenzenes that SAM has detected.

Posted by: stone Mar 30 2014, 09:07 PM

Benners work is one of the corner stones for all the people search for organics on Mars, but his carboxylic acids are a suggestion, there might be other compounds which are more stable. I know of no real good study on the survival rates and decomposition pathways of organic compounds so the real sink for organics is unknown. Benner suggested the aromatic carboxylic acids but he favored the mellitic acid which is not a good starting point to get to chlorobenzene. The to get from C6(COOH)6 to C6H5Cl needs at least 5H which are not available in the perchlorate mixture. The most likely way is oxidative chlorination of an C-H bond or an addition elimination reaction of a C-H bond, but for this you need a benzene or another not to oxidized aromatic compound.

The reactions in the gas phase during pyrolysis with oxygen and chlorine present make it hard to get the chemistry right and get the precursor molecule of the chlorobenzene right. Benzoic acid works fine, phenylalanine also works fine and the resulting compounds are always chlorobenzene and nothing else in the detection threshold. Ming did some experiments and could not find anything with melitic acid, so lets wait for Kimberley and Aeolis mons for better and richer samples.
[url="http://adsabs.harvard.edu/abs/2009LPI....40.2241M"]




Posted by: Don1 Apr 2 2014, 01:29 AM

These abstracts from LPSC give an update on the search for organics:
http://www.hou.usra.edu/meetings/lpsc2014/pdf/1157.pdf

http://www.hou.usra.edu/meetings/lpsc2014/pdf/2796.pdf

They are detecting chlorobenzene (6 carbon ring with a chlorine attached), chloropropanes (3 carbon chain with chlorine(s) attached) and chlorobutanes ( 4 carbon chain with chlorine(s) attached) which they think come from a martian source.


They see this in the Cumberland sample, but not in John Klein or Rocknest. These species are not produced when the contaminant MTBSTFA is reacted with perchlorate in the lab.

This result seems to me to be very tentative so it will be interesting to see if it survives peer review. Is the chemistry of these samples really well enough understood for MTBSTFA to be confidently ruled out as a precursor?

Posted by: stone Apr 2 2014, 06:32 AM

QUOTE (Don1 @ Apr 2 2014, 03:29 AM) *
Is the chemistry of these samples really well enough understood for MTBSTFA to be confidently ruled out as a precursor?


No, nobody ever did this before the SAM team started with putting MTBSTFA together with perchlorates. Here on earth every analytical chemist would wash away the perchlorates before starting to do derivatization. The problems you create if you don't if are so obvious. Most of the time you try to get ride of all inorganic salts and the inorganic matrix before you try to do experiments with the organic.

In N-(tert.-butyldimethylsilyl)- N-methyl-trifluoroacetamide the largest hydrocarbon fragment in the compound is the tert.-butyl group with 4 carbons while the next smaller fragment is the acetamide fragment which is only two carbons.

To get the two compounds chloropropanes (3 carbon chain with chlorine attached) and chlorobutanes ( 4 carbon chain with chlorine attached) might be possible from the tert.-butyl group but this reaction is not that straight forward because you have to lose one methyl group or you have to rearrange the chain.

The chlorobenzene is a little bit more complicated. Benzene is a standard pyrolysis product of many organic rich materials especially those not very volatile ones. To get it from the MTBSTFA is not absolute impossible, but unlikely. The clorination of the benzene is working very well with perchlorates so if you have a organic in the ground which releases benzene at higher temperatures you will end with considerable amounts of chlorobenzene.

The only place to get more information is the SAM testbed at Goddard and this is working all the time to get the the relevant experiments done.


Posted by: Gerald Jul 18 2014, 11:14 AM

http://astrogeology.usgs.gov/news/astrogeology/sol-691-update-on-curiosity-from-usgs-scientist-ken-herkenhoff-plasma- about ongoing analysis of the SAM results.
http://www.hou.usra.edu/meetings/8thmars2014/pdf/1349.pdf by testing a couple of possible origins within the SAM instrument. But they didn't find a quantitatively convincing scenario for the latter.

The precursor compounds aren't pinned down yet.
http://www.hou.usra.edu/meetings/8thmars2014/pdf/1201.pdf.

Posted by: Gerald Dec 5 2014, 10:28 AM

CheMin results of the Windjana drill sample, truncated and merged from the http://pds-geosciences.wustl.edu/msl/msl-m-chemin-4-rdr-v1/mslcmn_1xxx/data/rdr5/:

Mineral identifications, abundances and analytical errors for crystalline phases, other than clay minerals:

MINERAL,PERCENT,ERROR (estimated 2-sigma analytical errors)
PLAGIOCLASE,5.6,1.4
K-FELDSPAR,21.1,3.5
FORSTERITE,5.2,1.4
AUGITE,29,3.3
PIGEONITE,16.7,3.1
ENSTATITE,1,0.9
MAGNETITE,13.8,1.3
ANHYDRITE,1.4,1.1
BASSANITE,0.2,0.2
QUARTZ,0.2,0.2
HEMATITE,0.9,0.8
AKAGANEITE,2.5,1.2
PYRRHOTITE,1.3,0.8
ILMENITE,1.1,0.7

The mineral reported as K-feldspar is fit equally well as either sanidine or orthoclase.

The abundance of clay minerals was estimated ... at ~8.2 +/- 4 weight% of the total sample mass.

In addition to the crystalline phases ... ~20 +/- 11 weight% of this sample consists of X-ray amorphous material.

Posted by: Gerald Dec 5 2014, 02:39 PM

According to the PDS, SAM has performed an "Atmospheric methane enrichment" experiment, level 2 reduced data http://pds-geosciences.wustl.edu/msl/msl-m-sam-2-rdr-l0-v1/mslsam_1xxx/data/eid25206/level2/.
CH4 seems to have been identified by the TLS, file sm25206f0684rdr2__amet_tls_abundnc_1.csv:

QUOTE
"MOLECULE","VOLUME MIXING RATIO","ERROR"
"CO2 vmr",,
"H2O vmr",,
"CH4 vmr",0.90,0.16

I didn't find out absolute abundance, and can't assess, whether the methane is of Martian origin.
Hope, we'll learn more on http://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1759.

Posted by: serpens Dec 5 2014, 10:47 PM

While the SAM PDS results show Methane as 0.9 under a Volume Mixing Ratio heading, I suspect that the measurement is in fact parts per billion, assuming that they conducted enrichment studies for the Tunable Laser Spectrometer.

Posted by: Gerald Dec 6 2014, 01:41 AM

Not quite sure, whether http://pds-geosciences.wustl.edu/msl/msl-m-sam-2-rdr-l0-v1/mslsam_1xxx/data/eid25175/level2/sm25175f0558rdr2__spyr_tls_notesxx_1.txt is applicable to the amet_tls run, too, but it appears plausible:

QUOTE
The enrichment script was fully tested in the SAM test bed at GSFC to produce an enrichment factor of about 22. Provided data has this division already made to reflect the original Mars methane abundance with its correspondingly lower uncertainty.

The 0.90, with 1-sigma error 0.16, most likely referes to the volume ratio. The ratios for one analysis should sum up to 1.0, in theory.

As an example, sm25195f0637rdr2__adir_qms_atmcomp_1.csv (in http://pds-geosciences.wustl.edu/msl/msl-m-sam-2-rdr-l0-v1/mslsam_1xxx/data/eid25195/level2/) reads
QUOTE
"SPECIES","VOLUME MIXING RATIO","UNCERTAINTY"
"CO2 region 1",0.959,0.018
"40_Ar region 1",0.02,0.0002
"N_2 region 1",0.019,0.0005
"O_2 region 1",1.70E-03,2.00E-04
"CO region 1",6.20E-04,1.00E-04
"CO2 region 2",0.96,0.02
"40_Ar region 2",0.019,0.0002
"N_2 region 2",0.019,0.0006
"O_2 region 2",1.60E-03,2.00E-04
"CO region 2",4.00E-04,1.00E-04

Region 1 sums up to about 1.0, region 2 to exactly 1.0.

Posted by: Don1 Dec 11 2014, 08:14 AM

I'm fairly sure that the methane number is some kind of error. The mixing ratio reported is far too high for it to be real. Due to a construction defect, SAM brought a sample of Florida atmosphere with it to Mars, and that had methane in it.

If they ever do detect methane, I would expect a quick press conference.

Posted by: Don1 Dec 16 2014, 07:44 PM

The team just announced at the AGU that they did see a brief burst of methane at a concentration of 7 parts per billion (ppb). They think that the source is local to Gale Crater. There wasn't enough methane to measure the isotope ratio of C12/C13, which might provide clues to the source.

They are also reporting a detection of organics in the rocks at Cumberland, which was drilled a few years back in Yellowknife Bay. They speculate that the organics are associated with concretions in the rock. They do not detect high levels of organics in the recent drill sample at Confidence Hills, or at Rocknest or John Klein. They didn't discuss Windjana.

http://mars.jpl.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1767

Posted by: Don1 Dec 17 2014, 12:39 AM

Here are some miscellaneous notes about inorganic SAM results.


Hydrogen isotopes and water: From deuterium measurements it looks like Mars had 2-3 times as much water when Lake Gale was around, maybe enough to cover the planet to a depth of 100-150m. Deuterium measurements show that Mars had lost much of it's initial water before Lake Gale was active.

Confidence Hills: Grotzinger mentioned sulfates. Sulfuric acid forms sulfate salts, and it is oxidizing, which might explain the presence of hematite. This will make the current location less suitable for organics than Yellowknife Bay. Volcanoes emit sulfur dioxide, so Confidence Hills may record a more volcanic Mars.

Chlorine isotopes: Values in Gale Crater are lighter than Martian meteorites and there is a difference between Windjana and Yellowknife Bay. That is weird. Isotope separations are difficult, and only a few processes produce them.

Curiosity still has a leftover sample of Cumberland material in the lab, according to one of Emily's tweets.

SAM detected reduced carbon in the Rocknest dust. This could mean something like charcoal or graphite.

Mars magmas were apparently enriched in chlorine, and would have supplied hydrochloric acid to the atmosphere. It is worth noting that there is a very rich chemistry of organic molecules which contain chlorine.

Posted by: jmknapp Dec 17 2014, 12:56 AM

Going by the sols identified in the http://www.sciencemag.org/content/early/2014/12/15/science.1261713.full.pdf?ijkey=wh80Qt3dcQZKw&keytype=ref&siteid=sci, marked on the attached map are the sites where the increased methane was observed (7.19 +/- 2.06 ppb).



EDIT: I see they provided such a map in the http://www.sciencemag.org/content/suppl/2014/12/15/science.1261713.DC1/Webster.SM.pdf, figure 10.

Quoting from the paper:

QUOTE
The persistence of the high-methane values over 60 sols and their sudden drop 47 sols later is not consistent with a well-mixed event, but rather with a local production or venting that, once terminated, disperses quickly... The marginally higher daytime values suggested in sols 306 and 526 indicate a source to the rover's north, because prevailing daytime winds would advect toward the rover location... While we cannot rule out possible clathrate release or surface adsorption into the regolith with subsequent release, both these mechanisms do not support the local, short timescale variation we observe.

Posted by: marsophile Dec 17 2014, 04:35 PM

The methane press release refers to measurements made in late 2013 and early 2014. The PDS entry discussed earlier here reported on a methane enrichment experiment performed in July 2014. Also the value reported there does not seem to match the figures in the press release. Not sure what to make of that. I guess if it is PPB, it is consistent with the other measurements.

Posted by: jmknapp Dec 17 2014, 05:52 PM

The recent paper in Science discusses the enrichment runs including Sol 684 back in July. The enrichment runs allowed them to pin down the background methane concentration to a much tighter tolerance: 0.89 +/- 1.96 ppb for the "direct-ingest" runs vs. 0.69 +/- 0.25 ppb for the enrichment runs (95% confidence) .

It's interesting that they describe the TLS as having some methane contamination ("Florida air") in the foreoptics chamber, meaning the laser beam has to pass through 9cm of methane at tens of ppm levels before entering the main Herriott cell where it bounces many times between mirrors for a much greater path length (16.8 meters). So all the datasets show a methane signal and to get the level in the Martian air they must subtract the empty cell reading from the full cell reading. The raw empty cell readings show a much greater concentration of methane than the difference.

Posted by: Gerald Dec 17 2014, 06:01 PM

Table 1 in the appendix of http://www.sciencemag.org/content/early/2014/12/15/science.1261713 (free access via http://mars.jpl.nasa.gov/msl/mission/science/researchpapers/) contains a line

QUOTE
684 Jul 9th 2014 158.8 Night/4.5/2.7 0.90 ± 0.16 0.90 ± 0.32

This could correspond to the PDS entry. (I'm not yet quite sure.) In this case Serpens' suspicion (above) would have been correct.

Posted by: serpens Dec 17 2014, 10:55 PM

While correlation does not necessarily mean causation (and vice versa) the lack of correlation to key variables such as temperature, water vapour/oxygen abundance and terrain removes any easy paths to explaining the transient and low level methane readings. Transient is a bit of a rubbery description as we have no way of telling just how long each incident lasted. I can well understand why they put a lot of effort from a lot of highly qualified people into analysing these readings before releasing the findings.

Posted by: Mercure Dec 17 2014, 11:47 PM

...And the news has hit mainstream media ("methane burps"): http://www.independent.co.uk/news/science/nasa-finds-evidence-of-life-on-mars-9929510.html

Posted by: wildespace Dec 18 2014, 04:47 AM

Speaking of the media, Yahoo and Space.com somehow latched on the discovery of water at Cumberland:
http://news.yahoo.com/curiosity-rover-drills-mars-rock-finds-water-122321635.html
http://www.space.com/28030-mars-water-curiosity-rover.html

Please refresh my memory - hasn't this been anounced a while ago, and isn't exacly news? It was water locked in minerals, such as clays, right?

So unless I'm mistaken, the only real news is those spikes in levels of methane.

Posted by: James Sorenson Dec 18 2014, 05:33 AM

QUOTE (wildespace @ Dec 17 2014, 08:47 PM) *
So unless I'm mistaken, the only real news is those spikes in levels of methane.


The organics discovery is new as well. Just a heads up, the Discovery Channel is airing a documentary tomorrow at 10pm EST called "Red Planet Rover" featuring the new findings.

https://www.youtube.com/watch?v=TOhBDy4e_ec

Posted by: serpens Dec 18 2014, 06:52 AM

Not really new as they noted detection of di-chloropropane and chlorobenzene back in 2013 but whether Martian or contaminants from earth was open. I guess they are thinking chlorinated alkanes in the drill sample? Given that there was sometime between Phoenix's confirmation of perchlorates and mission launch I wonder if they investigated means of removing these oxidants in the first instance.

Posted by: jmknapp Dec 18 2014, 09:16 AM

The headlines just say "finds water," but if you read the articles they discuss the findings of the D/H isotope ratios in said water and what that implies for the timeline of water loss from Mars in the Hesperian period, which was the subject one of the two recent Science http://mars.jpl.nasa.gov/msl/mission/science/researchpapers/, and is new and exciting. "The imprint of atmospheric evolution in the D/H of Hesperian clay minerals on Mars" didn't really read.

As for the recent "definitive" announcement of Martian organics:

QUOTE
http://www.nasa.gov/content/goddard/mars-organic-matter/#.VJKe7SvnQ2s
December 16, 2014

The team responsible for the Sample Analysis at Mars (SAM) instrument suite on NASA's Curiosity rover has made the first definitive detection of organic molecules at Mars. ...

As part of Curiosity's plan for exploration, an important strategic goal was to sample rocks that represent different combinations of the variables thought to control organic preservation. "The SAM and Mars Science Laboratory teams have worked very hard to achieve this result," said John Grotzinger of Caltech, Mars Science Laboratory's Project Scientist. "Only by drilling additional rock samples in different locations, and representing different geologic histories were we able to tease out this result. At the time we first saw evidence of these organic molecules in the Cumberland sample it was uncertain if they were derived from Mars, however, additional drilling has not produced the same compounds as might be predicted for contamination, indicating that the carbon in the detected organic molecules is very likely of Martian origin."

Posted by: Gerald Dec 18 2014, 11:19 AM

As you indicate, there are worlds between some detector signal of chlorinated hydrocarbons and definitive detection of chlorinated hydrocarbons derived from organic compounds of Martian origin.

With respect to D/H: The presence of liquid surface water with 3-fold enriched deuterium in the Hesperian could mean much larger amounts of water in the Noachian, at least if the D/H ratio of Standard Mean Ocean Water is assumed for the initial D/H ratio.
This makes a much denser atmosphere on early Mars more likely, too.

Thinking at methane: Methane is a much more efficient (about 30x according to some sources) geenhouse gas than CO2. If high methane abundance is assumed for early Mars, maybe the temperature dilemma can be resolved.

Posted by: jmknapp Dec 18 2014, 01:19 PM

It's not as simple as saying that CH4 is X times as efficient as CO2 as a greenhouse gas. It's 38 times as efficient or whatever at the current relative concentrations in Earth's atmosphere. The effect of each gas on equilibrium temperature is logarithmic with their respective concentrations, so since CH4 is much less abundant, increasing it has a bigger effect, molecule for molecule (the absorption properties of the two molecules do not overlap significantly so their effects add independently). But comparing two atmospheres of pure CH4 and pure CO2 at any given molar concentration, CO2 wins as a greenhouse gas by far. And if CH4 dominated CO2 in concentration, then CO2 would be the stronger greenhouse gas, molecule for molecule. (see: Pierrehumbert, Principles of Planetary Climate, sect, 4.5.4)

Posted by: Gerald Dec 18 2014, 04:07 PM

So for an assumed water ocean, there should exist - within a certain temperature range - two solutions for a CO2 / CH4 atmospheric mix to result in a given mean temperature.
The idea seems to be not quite new, http://adsabs.harvard.edu/abs/1993emhw.workQ...3B.
Whereas http://arxiv.org/ftp/arxiv/papers/1405/1405.6701.pdf tries to discuss away the role of methane as a greenhouse gas in the early Martian atmosphere.

Posted by: jmknapp Dec 18 2014, 09:34 PM

To a first order, wouldn't it be a family of solutions, i.e., if you plotted the carbon dioxide vs. methane concentration to get a certain temperature given other assumptions, you'd get a curve?

The papers you link to are interesting as they give a hint at the conundrum brought up by the notion of a warm early Mars and the efforts over the years to resolve it in terms of radiative models, not altogether successfully. To higher orders there are all kinds of other factors, such as that carbon dioxide can condense, that methane is broken down by UV, that the effect of clouds is a big variable, and that average surface albedo is unknown, to name several. My impression from the recent methane results is that the main interest isn't in the atmospheric effects but rather whether it's the result of biogenesis, some other process, or perhaps some kind of as yet unidentified analytical problem. The mind-blowing thing about it is that taken at face value the episodic nature of it implies some kind of active process happening on Mars right now. Since that's an extraordinary result the team said in the supplementary materials that they have to hold out the possibility that it's an analytical error, but they investigated many such possibilities and were unable to find any such problem or alternative explanation (e.g., that the rover crushed some rocks in that area that released methane, etc. etc.).

PS Since they said the source was likely north of the short stretch where they observed the increased methane, I did a quick look at the images north of those sites. Here's a feature about due north:



The vent? smile.gif

Posted by: Gerald Dec 19 2014, 03:21 AM

With the CO2 / CH4 mix I've thought at the simplest-most set of scenarios, constant pressure, and a given mean temperature.
If the mean temperature is proportional to the logarithm of the abundance, we should get essentially something of the type
ln(1 + x) + ln(1 + (1 - x)) for x in [0;1],
for the mean temperature, in the most simple case, yielding one local maximum, hence two intersecting points with a horizontal line (the given mean temperature), as long as we stay below the maximum.
But of course, as we add further factors, things get so complex, that I'm not really surprised, that there isn't known a convincing solution.

If the measured methane is at least partially a result of http://en.wikipedia.org/wiki/Serpentinite (the "olivine + water + carbonic acid -> serpentine + magnetite + methane" - version), this process might have been much more intense on early Mars, hence could have possibly contributed to the warming by the greenhouse effect.
Partial oxidation of methane back to CO2 would have provided the mix for a combined absorption of sunlight.

Whether serpentinization or not, the surmised underlying methane-producing process could have been similar over billions of years, just slowed down by now, or today's presumed methane is a remnant of ancient methane production.

... Just an attempt to reduce observations to a small set of causes, well knowing that nature doesn't necessarily care about simplicity.

Posted by: Doug M. Dec 19 2014, 08:45 AM

QUOTE (Don1 @ Dec 17 2014, 01:39 AM) *
Mars magmas were apparently enriched in chlorine, and would have supplied hydrochloric acid to the atmosphere. It is worth noting that there is a very rich chemistry of organic molecules which contain chlorine.


Is there a cite for Martian magmas being enriched in chlorine?

Certainly there seems to be plenty of chlorine around at the surface. What's different from Earth is that while almost all chlorine on Earth is in the form of the chloride ion, on Mars we seem to be finding it both as chlorides and perchlorates. This implies a mechanism for oxidizing the former into the latter. (I've found one paper that seriously suggests static electricity from dust.) Perchlorates tend to react readily with organic molecules to produce chlorohydrocarbons, so the discovery of CHCs is consistent with a perchlorate-rich Mars.



Doug M.

Posted by: Doug M. Dec 19 2014, 03:03 PM

QUOTE (Doug M. @ Dec 19 2014, 09:45 AM) *
Is there a cite for Martian magmas being enriched in chlorine?


Never mind -- just googling "martian magma chlorine" turns up several. So, interesting!

-- Noted in passing: there are Earth microbes that can respirate perchlorate, using an enzyme called perchlorate reductase. Perchlorate is so high up the redox chain that this actually results in oxygen as a byproduct of respiration.


Doug M.

Posted by: jmknapp Dec 19 2014, 03:22 PM

QUOTE (Gerald @ Dec 18 2014, 10:21 PM) *
With the CO2 / CH4 mix I've thought at the simplest-most set of scenarios, constant pressure, and a given mean temperature.


OK, if you hold the pressure constant, temperature will be at a maximum for a certain CH4/CO2 ratio and for equilibrium temperature below that (but not too much lower) there will be two solutions as you say. The maximum will be very broad and flat except at the extremes, so the two solutions would be on the high CH4, high CO2 ends in general.

Posted by: TheAnt Dec 21 2014, 07:34 AM

QUOTE (Doug M. @ Dec 19 2014, 04:03 PM) *
-- Noted in passing: there are Earth microbes that can respirate perchlorate, using an enzyme called perchlorate reductase. Perchlorate is so high up the redox chain that this actually results in oxygen as a byproduct of respiration.


Correct, that's why the Phoenix result was considered to be that interesting.

As for the methane, we should not read too much into this measurement, the manner in which the level did go up do tell us one thing: It might have come from a relatively nearby location and probably from the subsurface of Mars.

Posted by: Gerald Dec 21 2014, 03:31 PM

QUOTE (jmknapp @ Dec 19 2014, 04:22 PM) *
OK, if you hold the pressure constant, temperature will be at a maximum for a certain CH4/CO2 ratio and for equilibrium temperature below that (but not too much lower) there will be two solutions as you say. The maximum will be very broad and flat except at the extremes, so the two solutions would be on the high CH4, high CO2 ends in general.

The rather flat maximum is a good point. It makes the radiative forcing of a CH4 / CO2 mix rather stable within a wide range of mixing ratios.
On the other hand it makes radiative forcing very sensitive to trace species.
In the context of an apparent contradiction of Kite's snowball model with a warm and wet early Mars (if one tries to avoid a highly variable climate), this makes me rethinking the SAM measurements of chlorinated hydrocarbons.
Perchlorates are thought to form photochemically in the atmosphere. But once chlorine is in the atmosphere, shouldn't we get a rich chlorine-organic photochemistry in the presence of methane? (http://repository.kulib.kyoto-u.ac.jp/dspace/bitstream/2433/46590/1/rpcjpnv15fp086.pdf.)
Complex chlorine-organic molecules once formed, should precipitate due to their higher boiling point, and become part of the sediments.
So couldn't either some of the found chlorinated hydrocarbons be taken literally, or, if the chlorine components are interpreted as a reaction product with perchlorates, these perchlorates partially be decay products of chlorinated hydrocarbons formerly in the Martian atmosphere?
The lack of a clear perchlorate signal (in contrast to halite) in CheMin data thus far - although exlainable by low abundance or amorphous modifications -, has also inspired me to think about alternative approaches.

Radiative forcing is known to be very sensitive to chlorinated hydrocarbons, at least on Earth, see e.g. table 2.3., on page 53 of https://www.ipcc.ch/ipccreports/far/wg_I/ipcc_far_wg_I_chapter_02.pdf.
Therefore the vague idea, that some of the possible inconsistencies could (or even should better) be resolved via adding chlorinated hydrocarbons to the (photochemical and climatic) models of early Martian atmosphere.

http://www.atm.ox.ac.uk/RFM/ (mainly of Earth) has been used in http://yly-mac.gps.caltech.edu/ReprintsYLY/A_RecentPapers/su%202012%20ch4/zjunk/ch4%20paper%20proofread/CH4%20paper_v11.21.pdf.
It considers overlapping absorption lines, inner-atmospheric radiation exchange, and includes several trace species.
Not quite sure, to which degree the sw and the paper are applicable to Mars, but the underlying physics should be similar, at least.

Posted by: ChrisC Dec 21 2014, 11:41 PM

QUOTE (James Sorenson @ Dec 18 2014, 12:33 AM) *
Just a heads up, the Discovery Channel is airing a documentary tomorrow at 10pm EST called "Red Planet Rover" featuring the new findings. https://www.youtube.com/watch?v=TOhBDy4e_ec

Does anyone know if this show is being repeated? I found out about it too late to set the DVR. I scoured the Discovery website (and the web in general) looking for rerun info, found nothing. I also asked them via Facebook, and will relay here if they reply. Surely they will rerun at some point ...

Posted by: jmknapp Dec 22 2014, 10:27 AM

It'll be interesting to see any results from India's orbiter with the Methane Sensor for Mars (http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=4423687&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D4423687) instrument that's designed to measure methane down to the surface over a long period of time with "several ppb" accuracy. Haven't heard anything yet though.

Posted by: Mr Valiant Dec 24 2014, 09:47 AM

Any chance the Methane spike may be due to interaction from Comet C/2013 A1 (Siding Spring)?
Shame the isotope ratio is out of range as we could've compared it to results from Rosetta.

Posted by: Hungry4info Dec 24 2014, 12:30 PM

From: http://www.fromquarkstoquasars.com/curiosity-detects-methane-spike-on-mars/

QUOTE
Curiosity was able to detect two significant spikes of methane, one in late 2013 and once in early 2014
Siding Spring flew past Mars on 19 Oct 2014.

Something tells me the two are unrelated.

Posted by: stone Mar 17 2015, 09:59 PM

Looks like a few new results have been presented at LPSC. It looks like that the Cumberland sample was sitting in the MTBSTFA vapour from the leaking derivatization oven and now they found something.

Posted by: TheAnt Mar 25 2015, 05:27 PM

Nitrates detected by SAM in sediments. http://www.ltu.se/research/subjects/Atmosfarsvetenskap/Nyheter-och-aktuellt/Kvavefynd-mojliggor-liv-pa-Mars-1.128362?l=en.

Posted by: Gerald Aug 10 2015, 03:22 PM

I've read the link of the previous post, after doing the following analysis. So I'm sharing the nitrate conclusion, but with these new high NO values I'm sceptical about impacts as the main cause of nitrates for the new targets. Here my largely independent deduction:

An attempt to understand the http://pds-geosciences.wustl.edu/msl/msl-m-sam-2-rdr-l0-v1/mslsam_1xxx/data/eid25242/level2/. Particularly the high abundance of nitric oxide (NO) made me ponder:

QUOTE
"SPECIES","ABUNDANCE" (mole)
"1,3-bis(1,1-dimethylethyl)-1,1,3,3-tetramethyldisiloxane",2.00E-10
"tert-butyldimethylsilanol",8.00E-10
"tert-butyldimethylfluorosilane",7.00E-10
"2,2,2-trifluoro-N-methyl-acetamide",6.30E-09
"CH3Cl",8.20E-09
"CH2Cl2",6.00E-10
"HCl",1.47E-03
"H2O",5.70E-05
"CO2",2.70E-06
"SO2",3.03E-05
"O2",3.50E-06
"NO",1.24E-04
"H2S",2.88E-04


(The "Telegraph Peak" analysis of Sol 928 shows high NO, as well.)

Nitric oxide points towards the presence of nitrites, formed from http://www.nist.gov/data/PDFfiles/jpcrd11.pdf and release of oxygen. Ammonium-bearing minerals, like http://www.mindat.org/min-205.html, appear less likely, since http://core.ac.uk/download/pdf/10875643.pdf, at least, instead of NO.

KNO3 (between 550°C and 750°C) as well as NaNO3 (between 500°C und 750°C) form a quasi-equilibrium with the according nitites in the presence of oxygen:
CODE
2 NaNO3 <--> 2 NaNO2 + O2


https://en.wikipedia.org/wiki/Nitric_oxide#Preparation:
CODE
2 NaNO2 + 2 FeSO4 + 3 H2SO4 --> Fe2(SO4)3 + 2 NaHSO4 + 2 H2O + 2 NO


This kind of reaction may prevent the release of N2 or NO2 after the removal or reaction of O2 with other compounds during the pyrolysis.
The presence of other iron compounds might catalyse the decomposition of nitrites, as well.

https://msl-scicorner.jpl.nasa.gov/Instruments/CheMin/:
"As a result of the transmission geometry and the presence of a Mylar or Kapton window between the sample and the detector, CheMin will only detect elements with an atomic number greater than 12 (Mg) in the periodic table."
Hence NaNO3 is the more likely nitrate candidate. A high abundance of (crystalline) KNO3 is ruled out.

H2O and SO2 evolved during the SAM analysis.
http://eprints.qut.edu.au/2149/1/2149.pdf as found by CheMin.
H2O and SO2, together with some of the released O2, may provide the H2SO4 for the above release of NO from NaNO2.

http://pds-geosciences.wustl.edu/msl/msl-m-chemin-4-rdr-v1/mslcmn_1xxx/data/rdr5/
("The abundance of clay minerals was estimated ... at ~5 +/- 3 weight% of the total sample mass. In addition to the crystalline phases, a broad rise in background ... indicate that ~28 +/- 15 weight% of this sample consists of X-ray amorphous material.")
("column 2 lists the mineral abundances in weight percent")

MINERAL,PERCENT,ERROR
[http://www.mindat.org/min-3231.html] PLAGIOCLASE,55.1,4.5
[http://www.mindat.org/min-419.html] AUGITE,2.6,0.6
[http://www.mindat.org/min-3210.html] PIGEONITE,12.7,2.6
[http://www.mindat.org/min-1584.html; http://www.mindat.org/min-1458.html] FE-FORSTERITE,2.0,1.3
[http://www.mindat.org/min-2538.html] MAGNETITE,6.8,1.0
[http://www.mindat.org/min-3337.html] QUARTZ,1.5,0.6
[http://www.mindat.org/min-1856.html] HEMATITE,7.4,1.1
[http://www.mindat.org/min-2013.html] ILMENITE,0.9,0.4
[http://www.mindat.org/min-2078.html] JAROSITE,6.8,0.8
[http://www.mindat.org/min-1572.html] APATITE,4.2,1.2

The observed HCl might have been provided by amorphous Cl-akaganeite (considered e.g. http://www.hou.usra.edu/meetings/lpsc2014/pdf/1319.pdf).

The evolving H2S needs to be explained.
https://en.wikipedia.org/wiki/Hydrogen_sulfide#Production.
Iron sulfides are among the more stable sulfides. Candidate iron sulfides would be http://www.geochemsoc.org/files/5214/1270/1020/SP-5_117-132_Lennie.pdf, precursor precipitates for e.g. pyrite.

CheMin may not be able to identify "amorphous" FeS.
Besides reacting with acids to H2S, FeS could have been a precursor for amorphous Cl-akaganeite, jarosite (observed by CheMin), and the http://www.hou.usra.edu/meetings/lpsc2014/pdf/2709.pdf needed for the NO synthesis.

Traces of carbonates or organics may have provided the carbon for the evolving CO2, where organics appear more likely than carbonates in the acidic context.

https://books.google.de/books?id=tvS3J3dkEssC&pg=PA1&lpg=PA1&dq=photochemical+nitrate&source=bl&ots=PdV0Ff1rOS&sig=cxoRbQBuA6eF-POoDwpQxVJyQdo&hl=de&sa=X&ved=0CGkQ6AEwCWoVChMI1ZTz0t6exwIVAYUsCh3DogJz#v=onepage&q=photochemical%20nitrate&f=false.

Since FeS, as well as jarosite aren't very stable in a wet environment, my first idea for the formation of "Mojave 2" and "Telegraph Peak" would be a short-lived "salt lake" with nitrates and sulfates as "salts", the nitrates having undergone some transport and concentration. Akaganeite, jarosite, iron(II) sulfates may have formed mostly in-situ from "amorphous" FeS precipitated in the short-lived lake. For this, the lake should have beared H2S, e.g. from volcanism, and Fe ions from chemical weathering.
A longer-lived ("salty") lake or ocean would have needed a mechanism to seal the sediments before they could alter further. Therefore this latter option looks less plausible.

Posted by: Gerald Dec 4 2015, 06:33 PM

Chemin reduced data (file cmb_479423416min09230450450ch00113p1.csv (Telegraph Peak drill sample) in http://pds-geosciences.wustl.edu/msl/msl-m-chemin-4-rdr-v1/mslcmn_1xxx/data/rdr5/ says

QUOTE
MINERAL,PERCENT,ERROR
PLAGIOCLASE,38,3.5
K-FELDSPAR,5.9,1.1
AUGITE,2.1,0.5
PIGEONITE,7,1.3
ENSTATITE,2.8,1.1
MAGNETITE,10.9,0.7
QUARTZ,1.2,0.3
CRISTOBALITE,8.7,0.7
OPAL-CT,14.5,3
HEMATITE,1.6,0.5
ILMENITE,0.9,0.4
ANHYDRITE,0.5,0.2
BASSANITE,0.5,0.3
JAROSITE,2.4,0.5
APATITE,3,0.5


Interesting are https://en.wikipedia.org/wiki/Cristobalite and https://en.wikipedia.org/wiki/Opal#Microcrystalline_opal, together about 23% of the crystalline phase.
Together with quartz, it's more than 24% SiO2 of the crystalline phase.

The sample contained about 1/3 of x-ray amorphous material:
QUOTE
In addition to the crystalline phases, a broad rise in background is present and has been modeled using the program FULLPAT to indicate that ~34 +/- 12 weight% of this sample consists of X-ray amorphous material.

Posted by: Gerald Aug 2 2016, 12:29 PM

The scoop sample analysis (http://pds-geosciences.wustl.edu/msl/msl-m-chemin-4-rdr-v1/mslcmn_1xxx/data/rdr5/) of http://mars.nasa.gov/msl/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1883 (Gobabeb dune sample) revealed a high abundance of olivine:

QUOTE
...This table contains mineral abundances and analytical errors ... for the Gobabeb dune scoop sample...
In addition to the crystalline phases, a broad rise in background ... indicate that ~34 +/- 18 weight% of this sample consists of X-ray amorphous material...

QUOTE
MINERAL,PERCENT,ERROR
PLAGIOCLASE,35.8,1.8
OLIVINE,28,1.5
AUGITE,20.2,1.7
PIGEONITE,10.9,1.9
MAGNETITE,2.8,0.6
ANHYDRITE,1,0.3
QUARTZ,0.7,0.4
HEMATITE,0.5,0.3


Olivine is rather resistant to physical weathering, but weathers rapidly in the presence of liquid water.

Posted by: TheAnt Aug 7 2016, 09:14 AM

Light coloured veins seen in the bedrock in images from Yellowknife Bay have turned out to be sulphates (as was already suspected).
More interestingly is that they might have formed as a lakebed dried out.
The sulphate material were probably gypsum according to a study done at the http://www.alphagalileo.org/ViewItem.aspx?ItemId=166823&CultureCode=en.

Posted by: Don1 Aug 27 2016, 07:39 AM

From the GSA meeting abstracts:

"THE INVESTIGATION OF CHLORATE AND PERCHLORATE/SAPONITE MIXTURES AS A POSSIBLE SOURCE OF OXYGEN AND CHLORINE DETECTED BY THE SAMPLE ANALYSIS AT MARS (SAM) INSTRUMENT IN GALE CRATER, MARS"

" ... Previous SAM analog laboratory analyses found that most pure perchlorates and chlorates release O2 and HCl at different temperatures than those observed in the SAM data. Subsequent studies examined the effects of perchlorate and chlorate mixtures with Gale Crater analog iron phases, which are known to catalyze oxychlorine decomposition...... Overall, mixtures of perchlorates or chlorates with saponite provide the first explanation for the high temperature HCl releases in addition to the oxygen releases observed in Gale Crater materials.''

My comment: chlorates are ClO3 and are closely related to perchlorates which are ClO4.


"STRATIGRAPHIC DEPENDENCE OF CHLORINE ISOTOPE VALUES IN GALE CRATER"
"Previous work revealed δ37Cl values in Gale crater that are exceptionally light and more variable than any other measured material in the solar system (Farley et al., 2016), observations tentatively attributed to the unusual behavior of Cl isotopes in oxychlorine compounds.....new data reveal a statistically significant correlation between stratigraphic height and δ37Cl....a monotonic relationship between elevation and δ37Cl is observed."

My comment: This is weird. They have no idea why this is happening.

"OFF-PLANET GEOCHRONOLOGY: ONGOING RESULTS OF RADIOMETRIC AND COSMOGENIC DATING ON MARS"
"...Our first dating attempt was undertaken on the Cumberland mudstone (Farley et al., 2013), yielding a K-Ar age of 4.21 ± 0.35 (1σ) Ga, in good agreement with crater-density estimates of the age of the mudstone's likely source terranes of 3.5 to 4.1 Ga. A much younger (<2 Ga) and non-repeatable K-Ar age was obtained on the Windjana sandstone. We attribute this result to incomplete thermal extraction of 40Ar from the very Ar retentive phase sanidine..."
"The team is presently readying to deploy a two-step heating protocol that is designed to obtain a K-Ar date on jarosite in a mudstone called Mojave. "

My comment: It seems they have been having some trouble with their rock dating technique, which is probably why we haven't heard much about it in recent years. However there is another sample in the works, which aims to tell when Mars was making the sulfur mineral jarosite.


Posted by: marsophile Dec 17 2016, 12:53 AM

https://agu.confex.com/agu/fm16/meetingapp.cgi/Paper/143915

I've been wondering about the "spike" of methane. I recall that after Curiosity landed, it released a large amount of methane that it had apparently carried with it from Florida on Earth.

Is it possible that the later spike was due to passing through an area where the cloud of methane that was released had partially persisted? How rapidly would the released cloud have dispersed to the very low normal background levels?

[EDIT: It is clear from this paper
Mars methane detection and variability at Gale crater
http://science.sciencemag.org/content/347/6220/415
and the supplemental material that the release at landing was far distant in both time and space from where the spike occurred, so they are almost certainly not related.]

Posted by: marsophile Jun 8 2018, 01:23 AM

http://science.sciencemag.org/content/360/6393/1093.full

Extended measurements of the atmospheric methane show that large spikes recur, in addition to the regular seasonal variation. That would seem to rule out the suggestion about the initial release of Florida air.

Posted by: Dalhousie Jun 10 2018, 03:23 AM

QUOTE (marsophile @ Jun 8 2018, 01:23 AM) *
http://science.sciencemag.org/content/360/6393/1093.full


In parallel to the methane paper was this one about the confirmation of organic compounds up to C8 in samples from Confidence Hills and Mojave drill holes


Posted by: serpens Jun 10 2018, 08:27 AM

QUOTE (marsophile @ Jun 8 2018, 01:23 AM) *
.............. That would seem to rule out the suggestion about the initial release of Florida air.

Not at all. Measurements now measure methane reading in empty cell and then with martian air input and martian methane is the difference. We are considering extremely small concentrations.

Posted by: marsophile Jun 10 2018, 07:06 PM

I don't understand. How could the initial release of Florida air result in regular seasonal variations over several years at points far distant from the landing site?

I can see how pockets of Florida air persisting within the rover might result in random spikes for some time thereafter, but the suggestion I was referring to was that the rover might have passed through an external cloud of methane-enriched air from the initial release that had failed to disperse (but might have moved a little).

Posted by: djellison Jun 10 2018, 09:18 PM

QUOTE (marsophile @ Jun 10 2018, 12:06 PM) *
How could the initial release of Florida air result in regular seasonal variations over several years at points far distant from the landing site?


By continuing to leak out of the rover in temperature/pressure dependent ways.

Posted by: Dalhousie Jun 10 2018, 11:02 PM

QUOTE (marsophile @ Jun 10 2018, 07:06 PM) *
I don't understand. How could the initial release of Florida air result in regular seasonal variations over several years at points far distant from the landing site?

I can see how pockets of Florida air persisting within the rover might result in random spikes for some time thereafter, but the suggestion I was referring to was that the rover might have passed through an external cloud of methane-enriched air from the initial release that had failed to disperse (but might have moved a little).


After this length of time and the many purgings I'd be sceptical of this assertion. The efforts to write off evidence of Mars methane by some seem to become ever more desperate attempts of straw clutching.

Posted by: mcaplinger Jun 11 2018, 12:40 AM

QUOTE (Dalhousie @ Jun 10 2018, 03:02 PM) *
The efforts to write off evidence of Mars methane by some seem to become ever more desperate attempts of straw clutching.

It's not grasping at straws, it's good science. "Extraordinary claims require extraordinary evidence."

The paper has some discussion of alternative explanations, including contamination.

QUOTE
Although the TLS-SAM fore-optics chamber contains some terrestrial methane, this is too small an amount to be considered as a bulk source for later ingestion even if somehow contained within the rover instrumentation. By monitoring the fore-optics chamber pressure and methane content over the 5-year period on Mars, we see no evidence of gross leakage from the foreoptics chamber.


Posted by: serpens Jun 11 2018, 03:44 AM

QUOTE (Dalhousie @ Jun 10 2018, 11:02 PM) *
After this length of time and the many purgings I'd be sceptical of this assertion. The efforts to write off evidence of Mars methane by some seem to become ever more desperate attempts of straw clutching.

The fore-optics chamber is not purged. Small concentrations of methane have been measured in the Martian atmosphere and since that atmosphere is itself what we would classify on Earth as an industrial level vacuum the actual amount of methane is minute - but it is there. The seasonal variation in ppb must also take account of the cyclical variation in atmospheric pressure as CO2 transfers between summer/winter poles and this in itself means that the source of the methane spikes is not necessarily local. The real question is what causes the atypical spikes and at present no-one really knows. But I have seen no attempts to write off evidence of methane.

Posted by: Dalhousie Jun 11 2018, 04:36 AM

QUOTE (serpens @ Jun 11 2018, 04:44 AM) *
The fore-optics chamber is not purged. Small concentrations of methane have been measured in the Martian atmosphere and since that atmosphere is itself what we would classify on Earth as an industrial level vacuum the actual amount of methane is minute - but it is there. The seasonal variation in ppb must also take account of the cyclical variation in atmospheric pressure as CO2 transfers between summer/winter poles and this in itself means that the source of the methane spikes is not necessarily local. The real question is what causes the atypical spikes and at present no-one really knows. But I have seen no attempts to write off evidence of methane.



Kevin Zahnle has been an outspoken critic of methane on Mars on several occasions.

Posted by: marsophile Jun 11 2018, 05:34 AM

Methane signals due to contamination, if present, should show a gradually diminishing trend over time.

What are the prospects for Curiosity obtaining isotopic signatures of methane detections given enough time? Perhaps Florida air might have a unique and recognizable signature that could be distinguished even with rough measurements.

Posted by: serpens Jun 11 2018, 08:51 AM

Not really an outspoken critic surely. Kevin Zahnle agreed that the methane signature exists. He simply suggested that the spike could have come from the rover. At the time in particular that had to be a consideration.

Posted by: MrNatural Jun 11 2018, 12:45 PM

Could the methane be off-gasing from plastics on MSL? Or breakdown products of plastics exposed to UV and temperature swings?

Posted by: mcaplinger Jun 11 2018, 03:11 PM

QUOTE (MrNatural @ Jun 11 2018, 04:45 AM) *
Could the methane be off-gasing from plastics on MSL? Or breakdown products of plastics exposed to UV and temperature swings?

Read the paper, it's online. http://science.sciencemag.org/content/360/6393/1093.full

QUOTE
We argue against the possibility that the rover itself is a source of methane because we cannot identify any source large enough to produce even an instantaneous cloud of ~7 ppbv methane in a 10-m-diameter sphere around the rover...


Posted by: Dalhousie Jun 12 2018, 12:37 AM

QUOTE (serpens @ Jun 11 2018, 08:51 AM) *
Not really an outspoken critic surely. Kevin Zahnle agreed that the methane signature exists. He simply suggested that the spike could have come from the rover. At the time in particular that had to be a consideration.


Ge has reacted negatively to every major methane report since 2004. So he has got previous....

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