[X] My Assistant

[nprev]

Thank you, MC. My suspicious-sounding words undoubtedly did the man an injustice; he appears to be an exemplary journalist in many ways.

Perhaps the proper way to put my impressions is that there does not seem to be (as yet) enough specific information available concerning the methane discovery to modify MSL landing site decisions, and perhaps Mr. Covault's article reflected an ebullent optimism he detected from some of his sources which will undoubtedly subside somewhat after further consideration of the findings to date.

Don't get me wrong; if there's anything close to a localized CH4 emission site within MSL's capabilities to explore, that should be THE target, game, set, and match, siddown & shut up! I just think that it's a bit premature to discuss retargeting MSL based on this information at this time.

[mcaplinger]

Bottom line, there is very probably some substance to the MSL targeting story.

Covault's article says "The MSL rover's launch was recently delayed... but the slip could enable a new landing site selection related to the methane findings, says Michael Meyer, the lead Mars program scientist at NASA headquarters in Washington." I think we can safely assume that Covault didn't fabricate what Mayer said, but as you say, it's not much of a revelation. Given that the putative methane concentrations cover areas hundreds or thousands of km across, I'm not sure how anyone thinks MSL could land "near a vent" or what it could do if it did, but clearly there's lots of time to consider this.

FWIW, Covault has a slight taste for sensationalism; I think Mike Dornheim, who was killed in a car crash in 2006, did a better job of covering JPL for AW&ST.

[elakdawalla]

One of the press at the briefing (I didn't write down who) pointed out that Nili Fossae -- recently eliminated as a landing site option for MSL -- was one of the places that appeared to be belching methane, and asked if NASA would reconsider. Meyer replied that Nili was the most borderline of the landing sites from an engineering constraint standpoint, implying that its odds haven't really improved after this discovery. But then he went on to say that there were now two more years available for MSL landing site selections, and that things could still change, as the EDL capabilities of MSL will be better understood with time (implying that Nili may become less borderline).

--Emily

[imipak]

I hadn't heard of the concept of sub-permafrost liquid brines before the presentation, but searches on those terms finds some fascinating work investigating the phenomena on Earth by Dr Lisa Pratt, who was on the panel on Thursday. Much of it gets into non-UMSF topics, but focussing on the engineering requirements for a putative surface campaign to drill into such brines, it's noticeable these boreholes went down to more than 1000m. So, question: how far down would hypothetical Martian sub-permafrost brines be?

[silylene]

From Science Daily: http://www.sciencedaily.com/releases/2009/...90115164621.htm

"We observed and mapped multiple plumes of methane on Mars, one of which released about 19,000 metric tons of methane," said co-author Geronimo Villanueva of the Catholic University of America in Washington. "The plumes were emitted during the warmer seasons, spring and summer, perhaps because ice blocking cracks and fissures vaporized, allowing methane to seep into the Martian air."

I do wonder if the words ' plumes' and 'were emitted' bias the assumption of origin. I really do hope that the authors do find out in time that their words were chosen wisely!

Of course if all that methane came from one or several vents during the warm season, that would be a HUGE amount !

But let me analyze it another way. From the maps of Mars with methane levels, let's assume that high signals for methane were found conservatively over about 10% of the Martian surface (it actually looks more like about 20+%).

Assuming that methane is formed on about 10% of the Martian surface, and over a 90 day warm period, then the generation level is 13g/km^2/day, or about 0.000013 g / m^2/day. I do think this is not too much for a photochemical generation source. So I do wonder how a photochemical mechanism was dismissed as a source. I am very interested in reading this paper!

Calculation:
Mars surface area = 144 798 500 km²

19,000*2000/2.2 / (144798500*0.10) / 90 * 1000g = 13 g/km^2/day

13 /1000/1000 = 0.000013 g / m^2/day

[nprev]

Good analysis, Sily; thanks!

The issue at hand is really whether the methane is coming from vents (fractures or fumaroles), or from some sort of widespread low-yield chemical reaction on the surface. Obviously MSL is not presently equipped to detect the latter, nor are any of the operational orbital assets at Mars really capable of detecting transient phenomena like emission plumes unless a real stroke of luck occurs. Therefore, I'd have to call retargeting MSL to look for methane-emitting sites based on current information a highly risky strategy in comparison to, say, examining phyllosilicate beds which have been localized with a high degree of confidence.

[centsworth_II]

Remember about a year ago, NASA was deciding which of two would be the next scout mission to Mars?
As reported in The Planetary Society Blog, the two proposed concepts selected for further study were:

* Mars Atmosphere and Volatile Evolution mission, or MAVEN: The mission would provide first-of-its-kind measurements and address key questions about Mars climate and habitability and improve understanding of dynamic processes in the upper Martian atmosphere and ionosphere....
* The Great Escape mission: The mission would directly determine the basic processes in Martian atmospheric evolution by measuring the structure and dynamics of the upper atmosphere. In addition, potentially biogenic atmospheric constituents such as methane would be measured.... (my emphasis)

NASA chose MAVEN. I wonder how useful the methane measurements made by a Great Escape Mission would have been. I wonder how sensitive such a mission would have been to detection of possible unambiguous bio markers such as turpines. Maybe an upstart space agency, not NASA or ESA, will see this as a chance to get an orbiter to Mars to specifically map the methane and look for other organics. That would certainly be a feather in someone's cap.

[centsworth_II]

The issue at hand is really whether the methane is coming from vents (fractures or fumaroles), or from some sort of widespread low-yield chemical reaction on the surface. Obviously MSL is not presently equipped to detect the latter...

If the methane is coming from a "chemical reaction on the surface", MSL should see some mineralogical characteristics unique to those areas where the reaction occurs. If the reaction is photochemical, the reactive surface would have to be in plain sight.

[HughFromAlice]

From Science Daily: http://www.sciencedaily.com/releases/2009/...90115164621.htm

I do wonder if the words ' plumes' and 'were emitted' bias the assumption of origin. ........how a photochemical mechanism was dismissed as a source.

Great that you followed up these ideas. Very interesting and well thought out.

retargeting MSL to look for methane-emitting sites based on current information a highly risky strategy

I also agree with nprev's comments.

Maybe an upstart space agency, not NASA or ESA, will see this as a chance to get an orbiter to Mars to specifically map the methane and look for other organics. That would certainly be a feather in someone's cap.

I was just replying when I noticed that centsworth-II had basically just said most of what I was going to say and had said it better. So I hit the delete button. Anyway go India - China!

CH4 by photolysis - Anyway you stimulated me to check out in more depth info on the formation of CH4 by photolysis in the martian atmosphere. It looks like the topic is still under debate! For instance, "methane observed on Mars can be formed by photolysis of water vapor in the presence of CO, in addition to possible geological sources, rather than biologically" in Bar-Nun and Dimitrov in Icarus Vol181 March 2006 refuted by Krasnopolsky "One of the key reactions is effectively blocked by O2 in the martian atmosphere, and another key reaction does not exist. There are no pathways for effective formation of methane in the martian atmosphere" in Icarus 188 June 2007. Find via http://www.sciencedirect.com/

I'm getting more and more fascinated by all this........to the stage of being tempted to take out a subscription for Icarus!!

Thanks again Silylene!

[sci44]

Assuming that methane is formed on about 10% of the Martian surface, and over a 90 day warm period, then the generation level is 13g/km^2/day, or about 0.000013 g / m^2/day. I do think this is not too much for a photochemical generation source. So I do wonder how a photochemical mechanism was dismissed as a source. I am very interested in reading this paper!

Thats interesting - only 13g CH4/km2/day (1.3g/km2/day globally) - its not much to account for. Another possibility I havent seen mentioned yet is the formation of CH4 by Electrical activity within Dust Storms. There you have the energy input/heat plus the possible presence of catalysts in the dust, acting on atmospheric CO2 and traces of water:

Directly: CO2 + 2H2O + Energy -> (With catalyst/intermediate reaction) CH4 + 2O2

Or acting with any Olivine within the dust (see Juramike's post here too):
Indirectly: (Fe,Mg)2SiO4 + 4H2O + CO2 --> Mg3SiO5(OH4) + Fe3O4 + CH4

My question being: could lightning/electrostatic energy be another source of energy for this reaction - apart from volcanic heat/sunlight?

Again, just a bit of speculation, YMMV. Feel free to laugh me out of court..

[AndyG]

I'm having a hard time getting my head around the seasonality of a subsurface production. Assuming a regular generation and subsequent build-up of subsurface (abiotic) methane, vented when ice sublimes: how does new ice form to plug any "vents" year-on-year when that liquid is being lost over geological time?

That alone suggests a greater likelihood for photochemical production (or sci44's electrically-aided dust-storms - which could be easily tested by tying in observations to global dust-storm events?)

Andy

[Fran Ontanaya]

I hadn't heard of the concept of sub-permafrost liquid brines before the presentation

Dr. Peter Smith talked briefly about that possibility during the last Phoenix press briefing.

BTW, Nili Fossae/Syrtis Major seem to have plenty of olivine deposits.

http://hirise.lpl.arizona.edu/PSP_009652_2115
http://hirise.lpl.arizona.edu/PSP_010285_2090
http://hirise.lpl.arizona.edu/PSP_007411_2010

[centsworth_II]

how does new ice form to plug any "vents" year-on-year when that liquid is being lost over geological time?

Good question. Is it that water vapor continually escaping from beneath the permafrost through fissures freezes in winter to form the plugs but in summer it remains a vapor, leaving the surface? This would match the presence of water found along with the escaping methane.

As far as lasting over geologic time, there could simply be that much water down there. It'd be interesting to see a calculation of how much water is lost per year and what volume would be required to sustain the cycle for a given number of years. The vapor could be coming from a regionally fed liquid aquifer below the permafrost.

[lyford]

One of the press at the briefing (I didn't write down who) pointed out that Nili Fossae -- recently eliminated as a landing site option for MSL -- was one of the places that appeared to be belching methane, and asked if NASA would reconsider.

From the Dec. 04, 2008 MSL press release:

Based on discussion within the project and program, we would like to retain our current four finalists as the finalists for the 2011 launch, while retaining some flexibility for responsiveness to new discoveries.

(italics mine)

I wonder if this phrasing was deliberate?

[nprev]

Oh, definitely it was deliberate; my only question is on what basis they would decide to make a retargeting decision. Publically released information to date is inadequate for that.