[X] My Assistant

[Bill Thompson]

What is the latest on the origins or the existence of methane on Mars? Have there been any new thoughts or information.

This is my very first post here so I do not know who visits this forum and how current the information is.

[centsworth_II]

This is an excellent forum for serious discussion, often more up to date than news releases. However as far as I know, there is no "latest" on the methane question. I think we are all waiting for more data. Whether it might come from MRO, or from Rosetta as it flys by, from further studies by Mars Express or Earth-based telescopes, I don't know.

There are proposed future projects that address more directly the methane question, but as far as I know, none have been accepted for development. In the meantime the most discussed possiblilities are geothermal activity and life, but a less generally discussed possibility is methane produced by reactions between surface substances and solar radiation. This may turn out to be the case but is probably less discussed because it is not as exciting to most. If it is due to solar reactions, it will still be a difficult task to determine the precise reactions that are occuring. Of course there is always the possiblity of multiple sources.

I have no real expertise, but there are many in this forum that do.


Rosetta: http://www.esa.int/esaMI/Rosetta/ESA38F7708D_0.html

[Guest_AlexBlackwell_*]

I think there are some very informative posts on "martian methane" scattered across various threads. If someone marked them or pointed them out, perhaps a consolidation effort (to this thread?) would be worthwhile.

[Guest_AlexBlackwell_*]

I'll also mention that Oliver Morton's MainlyMartian blog has a good compilation of "martian methane" posts, which were really topical a year or two ago. You may wish to start here; however, I believe a few related discussions may be scattered throughout his blog, so scrolling through the archives may be required. The slog is well worth it, IMO.

[Guest_BruceMoomaw_*]

Yes, they very definitely are. There have also been a few relevant recent abstracts.

(1) From the upcoming COSPAR meeting ( http://www.cosis.net/abstracts/COSPAR2006/...e2f32646b163e72 0;

T. Encrenaz: "The detection of methane on Mars has been reported by several teams, in some cases tentatively, using both space and ground-based measurements. Krasnopolsky et al. (Icarus 172, 537, 2004) reported a mean CH4 mixing ratio of 10 ppb, from groundbased near-IR measurements. Using PFS aboard Mars Express, Formisano et al. (Science 306, 1756, 2004) announced possible variations over the disk with a maximum mixing ratio of 35 ppb. From high-resolution imaging spectroscopy, Mumma et al. (BAAS 36, 1127, 2004) reported the detection of localized hot spots with maxima as high as 250 ppb. These hot spots however were not confirmed by further PFS observations (Encrenaz, AGU, December 2005), which might imply a temporal evolution of these features. This talk will review recent observations devoted to the search for methane, and will discuss possible interpretation and further work."

Encrenaz also delivred a talk on this at December's American Geophysical Union meeting -- which I attended. At that talk, he specified that the Mars Express team now believes the overall range of methane they're seeing at different places on Mars to vary between 0 and 25 parts per billion rather than 35 parts; but they still see an average amount of 10 ppb. He remains puzzled by Mumma's ground-based detection of much higher local levels -- but he says that he personally finds Mumma's data "rather convincing", and wonders whether it may indicate dramatic changes over time. (Mumma's observations were made in March 2003.) He also totally retracted the team's earlier statement that they had also seen evidence of tiny traces of formaldehyde in Mars' air (which, if it existed, could have been made simply by the nonbiological oxidation of methane in the air).

(2) Carl Allen had an abstract at the latest LPSC meeting ( http://www.lpi.usra.edu/meetings/lpsc2006/pdf/1193.pdf ) on his recent photographic observations of Arabia Terra, one of the three regions which seem to have the highest concentrations of methane -- and which was already noted for having the highest concentration of near-surface water in some form (ground ice and/or hydrated salts) to be found anywhere near mars' equator, according to Mars Odyssey. This is clearly a very interesting region -- it also shows large numbers of layered outcrops, suggesting that it may be "an ancient sedimentary bed" -- but another paper concluded that the various mineral compositional instruments in orbit around Mars right now haven't seen anything unusual there in that particular respect. Clearly, however, it's worthy of much more study.

(3) There is still a lot of dispute over possible sources for the methane, either biological or nonbiological. One possible source -- a recent comet impact -- now seems to be ruled out as not containing enough of the stuff. But there's still a good chance that it comes either from volcanic venting or from "serpentinization" (the reaction of the mineral olivine, which exists in large amounts on Mars, with water, releasing hydrogen which in turn could react with small amounts of carbon in Mars' rocks to form methane). Another AGU talk by J. R. Lyons ( http://www.agu.org/cgi-bin/SFgate/SFgate?&...t;P53A-04" ) discussed this in more detail, but unfortunately I missed that talk.

(4) There is also the real possibility that it's being made by still-living underground Martian bacteria -- "methanogens" -- and some such bacteria have been discovered under Earth's surface, most recently in the strange sulfur-rich environment of Spain's Rio Tinto ( http://www.agu.org/cgi-bin/SFgate/SFgate?&...t;P42B-02" ).

At this point, any further actual data on Martian methane will have to come for the next few years from more observations either by Mars Express or ground-baed telescopes -- the Mars Reconaissance Orbiter isn't equipped to look for it. However, the 2007 Phoenix lander has some ability to detect it, and the 2009 Mars Science Lab should be able to do an extremely sensitive check for it -- including determining its isotopic ratios, which could give us more information on whether it's likely to be produced by living germs or nonliving processes.

[djellison]

One of Rosetta's instruments will be able to observe it as well I believe.

Doug

[Guest_AlexBlackwell_*]

See also two other threads here: "Methane Detection?" and "Abiotic Ch4 On Mars Via A Photoreductive Process."

[Guest_BruceMoomaw_*]

As proof that the "MARVEL" team plans to resubmit that methane-mapping mission as the 2011 Mars Scout, see the June 2004 presentation ( http://www-sosst.larc.nasa.gov/meetings/20...2-geofftoon.pdf ). However, since then, the addition of the atmosphere-oriented large 2013 Mars orbiter makes it more likely that the MATMOS instrument will fly on that craft instead.

[Guest_BruceMoomaw_*]

Another worthwhile recent abstract from Vladimir Krasnopolsky in the Feb. 2006 "Icarus" (Some problems related to the origin of methane on Mars"):

"The following problems related to the origin of methane on Mars have been considered.

"(1) Laboratory simulations of the impact phenomena confirm effective heterogeneous chemistry between the products of the fireball. This chemistry lowers the fireball freezing temperature from 2000 to 750 K for methane and to 1100 K for CO/CO2. Production of methane on Mars by cometary impacts is 0.8% of the total production. A probability that the observed methane on Mars came from impact of a single comet is 0.0011.

"(2) The PFS observations of variations of methane on Mars require a very effective heterogeneous loss of methane. Heterogeneous effect of dust is half that of the surface rocks. Thermochemical equilibrium requires production, not loss, of methane. Existing kinetic data show a very low efficiency of heterogeneous reactions of methane. Highly reactive superoxide ions generated by the solar UV photons on the martian rocks cannot remove methane. The required efficiency of heterogeneous loss of methane on Mars is higher than that on Earth by a factor of 1000, although the expected efficiency on Earth is stronger than that on Mars because of the liquid ocean and the abundant oxygen. All these inconsistencies may be removed if variations of the rock reflectivity contribute to the PFS observations of methane on Mars. The PFS data on H2CO, HCl, HF, and HBr also raise doubts.

"(3) Although geologic sources of methane are possible, the lack of current volcanism, hydrothermal activity, hot spots, and very low seepage of gases from the interior are not favorable for geologic methane. Any proposed geological source of methane on Mars should address these problems. Some weak points in the suggested geologic sources are discussed.

"(4) Measurements of 13C/12C and D/H in methane would be difficult because of the low methane abundance. These ratios are mostly sensitive to a temperature of methane formation and cannot distinguish between biogenic and low-temperature geologic sources. Their analysis requires the carbon isotope ratio in CO2 on Mars, which is known with the insufficient accuracy, and D/H in water, which is different in the atmosphere, polar caps, regolith and interior. Therefore, the stable isotope ratios may not give a unique answer on the origin of methane.

"(5) Ethane and propane react with OH much faster than methane. If their production relative to methane is similar to that on Earth, then their expected abundances on Mars are of a few parts per trillion.

"(6) Loss of SO2 in the reaction with peroxide on ice is smaller than its gas-phase loss by an order of magnitude.

"The overall results strengthen the biogenic origin of martian methane and its low variability."

[ljk4-1]

Normally I prefer not to post items with links to papers which are not generally
available online to everyone, but I think the subject warrants attention and those
who are interested in reading the full articles can and will search for them at their
library.

Yuichiro Ueno et al., "Evidence from fluid inclusions for microbial methanogenesis in the early Archaean era", 10.1038/nature04584, p 516-519 v 440, Nature, 23 Mar 2006.

http://www.nature.com/nature/journal/v440/...ature04584.html

Don E. Canfield, "Gas with an ancient history", p 426-427 v 440, Nature, 23 Mar 2006.

http://www.nature.com/nature/journal/v440/...ll/440426a.html

Summation quoted from panspermia.org, where I found the above items:

Microbes produced methane on Earth 3.5 billion years ago, according to Japanese environmental scientists. They found the methane in tiny fluid inclusions in quartz from Australia's Dresser Formation, whose age is known. Carbon isotope ratios indicate that the methane was probably produced biologically. If so, methanogens were active on Earth 700 million years earlier than previously thought. Intriguingly, the microbes may have lived as much as a kilometer deep underground.

Methane is an effective greenhouse gas that would have helped to warm the planet when the sun was dimmer. Methane is also present in the atmospheres of other planets, and moons like Saturn's Titan. We wonder if they could be at stages through which Earth passed earlier.

[mwolff]

Encrenaz also delivred a talk on this at December's American Geophysical Union meeting -- which I attended. At that talk, he specified that the Mars Express team now believes the overall range of methane they're seeing at different places on Mars to vary between 0 and 25 parts per billion rather than 35 parts; but they still see an average amount of 10 ppb. He remains puzzled by Mumma's ground-based detection of much higher local levels -- but he says that he personally finds Mumma's data "rather convincing", and wonders whether it may indicate dramatic changes over time. (Mumma's observations were made in March 2003.) He also totally retracted the team's earlier statement that they had also seen evidence of tiny traces of formaldehyde in Mars' air (which, if it existed, could have been made simply by the nonbiological oxidation of methane in the air).

At this point, any further actual data on Martian methane will have to come for the next few years from more observations either by Mars Express or ground-baed telescopes -- the Mars Reconaissance Orbiter isn't equipped to look for it. However, the 2007 Phoenix lander has some ability to detect it, and the 2009 Mars Science Lab should be able to do an extremely sensitive check for it -- including determining its isotopic ratios, which could give us more information on whether it's likely to be produced by living germs or nonliving processes.

three quick points:

1) Encrenaz's first name is Therese...so references to "he" may be problematic.

2) Mumma's column abundances are model-dependent. his analysis techique is driven by the detection of methane using a ratio technique, which does not directly retrieve an absolute abundance of methane. he uses a model which is tied to retrievals from different data and which attempts to correct for the amount of atmospheric aerosols which would tend to underestimate the amount of any volatile (i.e., water) if not explictly considered. it is the model steps that are most problematic...

3) MRO CRISM observes in the 3 micron methane band...if enough methane is present. if there were 200 ppb present, CRISM (as well as MEX/OMEGA) would very likely be able to see it.

As proof that the "MARVEL" team plans to resubmit that methane-mapping mission as the 2011 Mars Scout, see the June 2004 presentation ( http://www-sosst.larc.nasa.gov/meetings/20...2-geofftoon.pdf ). However, since then, the addition of the atmosphere-oriented large 2013 Mars orbiter makes it more likely that the MATMOS instrument will fly on that craft instead.

the MARVEL PI would probably pale to hear his mission described as a methane-mapper Other Scout mission proposals will also include methane detection capability (through both indirect illumination and occultation techniques).

While it will be interesting to watch, it is important to recognize that MEPAG is not NASA and that MEPAG's recommendation for an atmospheric orbiter in either 2011 or 2013 is not likely to carry much weight in itself; particularly in the current budget climate.

[Guest_BruceMoomaw_*]

It wasn't MEPAG that recommended a 2013 orbiter to NASA -- it was the other way around! Because the overspecialized 2009 Mars Telecom Orbiter has been cancelled, and because MRO's design lifetime is only a decade, NASA has decided that they will need to launch more combined science/communications orbiters at the rate of about once/decade to provide their future landers with the communications capability that they need. They therefore ordered MEPAG to recommend the best science payload for the orbiter which they'll be launching in 2013 in any case. And MEPAG, as was made clear at the November COMPLEX meeting, was strongly oriented toward atmospheric investigations for that orbiter from the start.

You're certainly correct that MARVEL would serve functions besides methane-mapping -- it was a mapper of all sorts of trace gases, as well as providing a lot more data on altitude profiles of air density, dust, and (I believe) air temperature. But the instruments that it would have used for that purpose are all now included on MEPAG's recommended payload list for the bigger 2013 orbiter (along with all the instruments recommended by several past groups for a Scout-class Mars Aeronomy Orbiter for upper-atmospheric studies).

There is also another good reason for flying an atmospheric orbiter this early -- it's been made clear both by MEPAG and by other NASA engineers that we very badly need more data on the the fluctuations in Mars' upper air density, and its lower-altitude winds and turbulence, to maximize the safety of future landers. (Oddly, this wasn't listed among the 2013 orbiter's goals in the MEPAG document - maybe because MEPAG was just ordered to provide recommendations as to the purely scientific uses of a 2013 orbiter. But the instruments required for both types of studies are almost identical.)

[mwolff]

[snip]

They therefore ordered MEPAG to recommend the best science payload for the orbiter which they'll be launching in 2013 in any case. And MEPAG, as was made clear at the November COMPLEX meeting, was strongly oriented toward atmospheric investigations for that orbiter from the start.

[snip]
There is also another good reason for flying an atmospheric orbiter this early -- it's been made clear both by MEPAG and by other NASA engineers that we very badly need more data on the the fluctuations in Mars' upper air density, and its lower-altitude winds and turbulence, to maximize the safety of future landers. (Oddly, this wasn't listed among the 2013 orbiter's goals in the MEPAG document - maybe because MEPAG was just ordered to provide recommendations as to the purely scientific uses of a 2013 orbiter. But the instruments required for both types of studies are almost identical.)

That's bad news for Scout PIs proposing an atmospheric mission (of which there are an amazing number)...though I suppose it will make proposal preparation easier if NASA allows complete payload proposals for 2013.

"lower altitude winds" will be very difficult, unless they are only talking about measuring down to 20 km.
Microwave techniques suffer from pressure-broadening (of lines) below 20 km and interferometric techniques typically use an emission line of molecular oxygen which is collisionally quenched below 20-25 km. so
the bottom two scale-heights will be hard to get (one can use absorption lines as long as one looks at the
surface -- as opposed to the limb -- but there are other technical issues.

there are several aeronomy mission concepts, so they will have something to cheer even if they don't win in 2011.

thanks for providing the info about COMPLEX. i have to admit, i am still very skeptical about NASA actually following up on an atmospheric orbiter...but your statements provide insight into the number of aeronomy scout missions concepts.

[Guest_BruceMoomaw_*]

That's bad news for Scout PIs proposing an atmospheric mission (of which there are an amazing number)...though I suppose it will make proposal preparation easier if NASA allows complete payload proposals for 2013.

"lower altitude winds" will be very difficult, unless they are only talking about measuring down to 20 km.
Microwave techniques suffer from pressure-broadening (of lines) below 20 km and interferometric techniques typically use an emission line of molecular oxygen which is collisionally quenched below 20-25 km. so
the bottom two scale-heights will be hard to get (one can use absorption lines as long as one looks at the
surface -- as opposed to the limb -- but there are other technical issues.

there are several aeronomy mission concepts, so they will have something to cheer even if they don't win in 2011.

thanks for providing the info about COMPLEX. i have to admit, i am still very skeptical about NASA actually following up on an atmospheric orbiter...but your statements provide insight into the number of aeronomy scout missions concepts.

I have a whole series of statements on the goals of the 2013 mission on the "MTO Cancelled" thread down in "Past and Future". You're entirely right about the difficulty of measuring near-surface winds; but -- as that thread says -- it may not be impossible, especially for an atmosphere as thin (and dust-rich) as Mars' is. Any one of three techniques MIGHT work for that, and MEPAG at the moment seems to be putting its money on microwave limb sounding.

They seem to be really solid on the 2013 orbiter being atmosphere-focused -- and one of the reasons is that MEPAG has now officially listed upper-atmophere aeronomy and lower-atmosphere trace-gas mapping as important Mars goals that have been neglected in past MEP plans (along with seismic and heat-flow measurements). MEPAG's group gave some consideration to trying to add SAR mapping of the near-subsurface bedrock features below the soil layer to this mission as well, but finally decided that would be pushing it. (Besides, they need some new science goal for the next science-and-com orbiter around 2022...)

This mission seems to knock MARVEL pretty much out of contention for the 2011 Mars Scout. My very tentative guess as to the 2011 Scout is SCIM (which is indeed being re-proposed). But there are also at least two Mars airplanes being proposed, plus one Scout-class SAR orbiter.

[mwolff]

You're entirely right about the difficulty of measuring near-surface winds; but -- as that thread says -- it may not be impossible, especially for an atmosphere as thin (and dust-rich) as Mars' is. Any one of three techniques MIGHT work for that, and MEPAG at the moment seems to be putting its money on microwave limb sounding.

it is the dust that is causing the trouble with the optical techniques...in the absence of dust, it would be very straight-forward to
retrieve winds below 20 km (though not with the typcial O2(singlet-Delta) transition). without dust, one could simply do ray-tracing
instead of the much more prohibitive multiple-scattering radiative transfer.