Speaking of-- and feel free to delete or move this comment-- but Craig Covault was let go by Aviation Week and is now working for spaceflightnow.

As I've said elsewhere in similar discussions - accusations of baby out with bathwater are expected, and at least partially justified. But that's the price that I consider worth paying. Emilys posts explains it very very well.

No - I don't think I'm some internet god. But I fail to see why people go 'Wahahh - I want to talk about X'. What is stopping them doing that? Nothing. Find a place where it's allowed, and do it. I don't complain that I can't talk about manned spaceflight, or religion, or biology, or politics, or other off topic stuff. I stick to the rules and find somewhere else to talk about the issues I want to talk about that are not within the remit of UMSF.

UMSF is, intentionally, about a very very small subject area. S/N ratio is the currency of forums, and this one is, fortunately, quite high. I don't intend to risk it on subject matter that is, at its core, off topic. What is and isn't acceptable in a forum is more than just reading it's URL and assuming that's it.

Doug

Any ideas as to whether current Mars orbiters with radar have studied the undersurface of such regions on the planet releasing Methane gas?

I couldn't help noticing that two of the panelists have a close association with the MEX-PFS instrument. Sushil Atreya (a thorough gentlemen) is on the PFS team and Geronimo Villanueva is Official Reviewer of the MEX-PFS Archive. I'd have liked to hear MUCH more about how Mumma's work might help sort out the genuine problems with PFS calibration. Can Vittorio Formisano go back and recalibrate?

i do wish that the researchers did not seriously consider photochemical generation of methane as a significant source of abiogenic methane.

Please refer to this thread, or even older threads in SDC (with many references) : http://www.unmannedspaceflight.com/index.p...&hl=methane

From the synopsis of the press conference I read on SDC by MW (sorry, I missed the press conference): I would like to see chemcial kinetic rate data that photolysis takes 'centuries', or was this a conjecture? It would need to be a steady state effect: methane is both being produced and being lost. The concentration observed reflects the chemical kinetics of these two processes.

The map of methane production shown (I recall we went over this before, in the pre-Pluck and also pre-crash SDC forums), and indeed in the pre-crash SDC also!) gives the highest methane production in the Martian equitorial band. This is exactly what would be expected if it were a photochemical process, since this would occure in the areas of highest irradiance.

The photochemical process I proposed (see the link above, or for more information, the older links in SDC) was a photoreduction of CO2 catalyzed on metal oxide dust surfaces with hydrogen (which comes from water). The dusts (TiO2, for example, this works with several types of oxides) serve as catalysts for this effect. in fact, I would expect areas in which the dust is uplifted due to winds or dust devils to expose more dust catalyst for methane photoproduction. So you may see the highest rates where there is both high irradiance, and higher concentrations of exposed metal oxide dusts. I also recall about 2 yrs ago that, I came across a paper which found some atmospheric photoreduction chemistry occuring on the dusts from the soil surfaces in Chile'se Atacambra desert, which is a rather good stand-in for the Martian conditions.

Also, one would need to correlate the seasonal variation lifting or exposure of exposure of dusts which may serve as catalysts. And/or correlate the seasonal variation in the concentration of H2O in the atmosphere may be inportant too, as this is the source of H2 for the photreduction of CO2 to methane.

Until I see more, I am very unconvinced of the need for a biogenic methane source. I am looking forward to reading their journal paper to see how they treated the photochcemical generation.

FWIW, looks like the observations were purely Earth-based, from the Mauna Kea observatories.

http://www.spaceref.com/news/viewpr.html?pid=27373

If that is correct it does go against a biological source, you'd expect microbes to be concentrated in areas where water ice was more common and there was some chance of liquid water.

I just hope we NEVER get back a picture from Spirit or Oppy with a critter perched on one of their solar panels! We wouldn't be able to talk about it! We could, however, play with various projections of it.

This is the last i'm going to say on this issue, but I felt I had to respond.

More and more of NASA's research and discovery aims are becoming astrobiology related as a result of the unmanned spacecraft visiting more and more destinations. Possibile subsurface oceans on Europa and Ganymede... and the latest discoveries at Enceladus by Cassini. I remember the tremendous excitement and anticipation surrounding Opportunity's first discoveries at Meridiani relating to water and possible past habitability. Phoenix and the polar Ice too. The future MSL will have a substantial astrobiology element to the mission.

These latest results will surely have an impact on future design and instruments to be sent to Mars which is why I found the suggestion that people could be banned or suspended for discussing them truly astonishing.

Then talk about them in a different forum - what's stopping you? People get banned or suspended for breaking the rules. The rules are there for everyone to see. People get warnings and a heads up when they're running the risk of breaking those rules. We even gave a specific warning in this very thread.

If someone gets banned - it's because they refuse to respect the rules.

UMSF was started, as you will remember, as a place for people to share their mosaics, and talk about what the MER's were up to. Its scope has grown and grown and grown for 5 years. Lines have to be drawn to dictate what is an isn't allowed to maintain the S/N ratio for those topics for which the board was started. Biology, like Politics, or Manned Spaceflight - has baggage. It has too much scope for arguments, bickering, personal ranting campaigns - and in the specific case of biology, fringe theory nut jobs.

Now, we can try and accommodate that subject and spend, literally, hours trying to keep things at a reasonable level, get accused of bias or inconsistent treatment - and the end result is the very occasional interesting topic and an enormous quantity of unseen administrative workload, annoyance, hassle, insults, accusations and entirely unjustified stress.

OR - we can simply say no to that subject entirely, giving admins and mods little bits of their lives back, keeping the ammount of administrative workload to a minimum - and above all, maintain the S/N ratio of the subjects for which this forum was started and is maintained.

If you want to talk about Biology, try the www.bautforum.com - it's brilliantly maintained, conducive to interesting discourse, and a perfect home for that sort of discussion. It's what I do - and I can see no reason why anyone else would object to doing the same.

Oi, if there's snow, snow will be studied, not polar bears.

The detection of plumes sounds interesting. I hope the sources can be pinpointed with HiRISE imagery.

I just posted a summary of a proposed mission to follow up on the methane discovery at http://futureplanets.blogspot.com/2009/01/...rs-methane.html

Ok, we´re all getting serious and discussing signal to noise ratio et al, but just remember one thing: this is a discussion of whether something has been farting or not. How serious is THAT?

Thanks for the interesting summary on your blog, VJ!

Question for the chemists out there: Are CO2/CH4 clathrates possible? Reason I ask is that IIRC the frosts at the V2 site were thought to be 6:1 CO2/H2O clathrates. Wondering if the seasonality might reflect sublimation of a CO2/methane mix, which presumably would have different physical properties.

Of course, that would not explain the origin of the methane unless it's truly primordial & the clathrates are ancient.

Are CO2:CH4 clathrates possible?

If you mean CO2 trapped in a methane cage structure....No I don't think so.

The cage structure relies on intermolecular hydrogen bonds to set up a cage structure. So the "cage former" requires some sort of polar atom to hook up to other buddies with a healthy strong hydrogen bond interaction.

CH4 is pretty much a boring little tetrahedral greaseball: Not good for making cages. So the strongest bond you could get would be a non-polar dispersion ("VanderWalls" is a passe term these days) interaction of a hydrogen atom dispersing into the orbital cloud of another methane molecule. Very, very low lattice energy. Theoretically, it *might could* form a cage, but I would think it would need to be at temperatures approaching absolute zero to make any type of cage structure.


-Mike

Sounds less stable than me after an hour without a beer. Thanks Mike, as always, for the lucid and readable explanation!

The rules page is quite a read itself...
Simple, yet undeniable...
All Hail UMSF...

While there will be an awful lot of study and theorizing about the source(s) of the observed methane, and an awful lot of modeling of said sources, I think perhaps one of the things that needs to be really pinned down hard before those models gain any credibility is the volume of methane being released over time. I know they have some figures right now, but they're only showing plumes in three small-ish areas of Mars. Are those the *only* sources? Or have we not looked closely enough at the rest of the planet to find others?

Once you know how much you're releasing, you can project total release levels over much longer periods, like millions and billions of years. If it turns out, for example, that the current release rate (which is really very low on a planetary scale, I believe) would over a billion years require that a methane ocean has to have been sealed up and slowly leaked out over that period, that makes the ancient origin theory unlikely. If it would only require a few thousand tons of clathrated methane, spread out over only perhaps several thousand total cubic kilometers (a very small percentage of Mars' upper crust), then the ancient origin theory looks a lot better.

If the release volume, as projected against a variety of assumption sets, seems to require constant (if very low-level) production of methane over time, then the various other theories gain more ground.

(And yes, I know that release rates have probably changed over time. You can plug such changes into the release-over-time models, if you wish, as long as your changes are in some way supported by actual data.)

One thing that was just mentioned at the press conference (I recorded it on my DVR and am watching it now) is the possibility that there might be a layer of permafrost under the entire Martian crust, even the equatorial plains. Do we have any real evidence of this from either of the radar experiments? Or is this simply another model they're tossing around?

More and more, I want to get heat flow data from Mars. An awful lot of what's actually happening under the first few km of Mars' crust depends on the temperature regimes of its crust, mantle and core. We have very little idea of how much remanent heat may yet be contained within the planet, how heterogenous (or not) its distribution might be, and very specifically at what locations and depths water (and other things, like methane) might exist as solids, liquids and even gasses.

-the other Doug

"Other" Doug - I think you have raised interesting points.

My interest is in what the next generation of Mars orbiters and ground based craft should be looking at. Mumma noted that our past focus on following geology/minerals lead to the choice of Meridiani as the landing site for Opportunity and to the subsequent 'cornucopia of information' culminating with evidence of standing water on Mars. Now we need to target missions to investigate active areas.

He was also at pains to point out that his data analysis and control of instrumental artifacts was 'unassailable for any point of view"!! Is there anyone in UMSF really up in spectroscopy that has read Mumma's recent Science paper and would like to comment on the algorithms/techniques he used? Would be interesting to hear from an expert.

I thought a lot of really key things in this press briefing came out towards the end as the panel loosened up after a few questions from the audience.

Villanueva noted that a lot more can be learned from going back to their (massive) data sets (and CRISM data sets for gen mineralogy) in the light of these results. Particularly checking how old the water is that has been detected along with CH4. Old production - new release or new production - new release? He then commented that they are doing this and will submit a paper for publication soon. Also Mumma made allusions to more papers to come soon - such as looking at seasonal repeatability.

Mumma pointed out that if 'bio' is near the surface then it should be using water that is in contact with the atmospheric escape and so will have a high D content. But water below permafrost is ancient and likely to be much lower in D. Then to throw the cat among the pigeons, Pratt pointed out that we know very little about D/H ratios due to radiolytic splitting of water. (So we need to do more research here on earth before anything else!!).

She continued that CH4 and D/H ratios would not be enough for absolute proof anyway - we would need to positively identify a suite of biomarker gases like turpines etc. etc. If we can't do this, we will need to drill down and pump water out! She pointed out that to verify life that exists in thin films deep underground on Earth it is necessary to filter 100,000s of litres of water and then either visually identify the life forms or grow them! We'll need a mighty spacecraft to drill and pump!!! Mars Science Laboratory might get very very lucky and sample concentrated gases at a release point which would - at least - give us strong indicators.

Sushil Atreya also commented that we need to look on the ground for heavy hydrocarbons. If ethane and propane were found then geo source would be more likely. Mumma said that they have began to look at this in 2006 and that there will be a publication later in the year. Another one?

For me the most interesting comments of all came from Lisa Pratt. She pointed out that it is much easier to make a living consuming methane than excreting it. There is an enormous amount of sulphate on the surface of Mars. Sulphate reduction coupled to methane oxidation starts to look like a very attractive proposition. On Earth, this metabolism in one of the most ancient ones. So if methane is coming out in focused areas then it gives us a bull's eye to go in and search.

Now that's what I call a really exciting hook to get priority funding for new missions to Mars ---- despite my fascination with Titan (especially) and Europa!!! After all, if that wonderful memorandum of mammary masterpieces - the UK paper 'The Sun' - found it worthwhile to go to the trouble of making a major scoop on a Mars story for its readers, then the pollies might actually see a few votes in it!!!

I'll read it hopefully today and report back my thoughts. (I am a PhD polymer photochemist).

Well researched. A theory is that water, iron oxide, C02 from the atmosphere, and volcanic heat could cause reactions resulting in methane production. However... we have yet to see evidence of ongoing volcanism (not that it's conclusive, we just don't have the evidence there).

Given results from various orbiters and Mars Phoenix Lander, there is plenty of evidence to support the possibility of bacterial life on Mars.

We've found plenty of water-ice, the other chemicals (perchlorates, etc) we've found do not eliminate life (as we know it) as a possibility.

Everywhere we find water on the Earth, we find something living in it.

In any case... it's pretty neat!

[the other] -Mike

---

Not to mention the levels of UV - once at the surface, any sort of "cage" or structure in the methane would probably be "blown-apart" by UV.
Methane "wants" to come-apart.

There is one ingredient for habitability that, as far as I know, we have not yet found on Mars: nitrogen (except for small amounts in the atmosphere). Please correct me if I am missing something.

I thought that there was in fact a small fraction of nitrogen (3%?) detected in the atmosphere by the Vikings.

BTW, the lead story on spaceflightnow.com now (sic!) implies that MSL retargeting might be under consideration as a result of this discovery. The story seems a bit overblown to me. IIRC, it was written by the same journalist that experienced some controversy regarding perchlorates in the Phoenix samples...please correct me if I'm wrong, anybody.

Craig Covault. Considered by many folks as one of the top aviation and space journalists. Accolades when he was recently let go by Aviation Week:

http://www.nasawatch.com/archives/2008/11/...ay_for_avi.html

I enjoyed reading his AvWeek articles years ago when I had time to go to the library and read AvWeek. He gets leads that very few other writers get. E.g., his recent article in Spaceflightnow:

http://www.spaceflightnow.com/news/n0901/14dsp23/

Bottom line, there is very probably some substance to the MSL targeting story. Giving more consideration to one of the landing sites in light of recent discoveries is not exactly earth (or Mars) shaking. How much more consideration, we will have to wait and see.

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.

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.

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

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?

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

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.

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.

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.

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



I also agree with nprev's comments.



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!

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..

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

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

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.

From the Dec. 04, 2008 MSL press release:
(italics mine)

I wonder if this phrasing was deliberate?

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.

For information - we have discussed the biology issue in the Admin section. The discussion came to a very near unanimous decision that the outright ban on Biology is the right step for UMSF at the moment. Reasons cited include those I've mentioned before, as well as others. In no particular order

- Biology (like Politics or Manned v Unmanned) takes on a religious like status in peoples minds with no grounds for actual debate
- There are no biological instruments flying, or planned for flight.
- Setting a limit for what would or would not be acceptable would be near impossible. There is no fair or valid means to half-open the door on this.
- The administrative workload would increase significantly (high admin workload being the sign of a badly administered forum)
- There are alternate venues that are better suited to these sorts of discussions.

It is by taking difficult decisions like this one, that UMSF has become and continues to be what people admire it for. Such decisions are, to some extent, a judgement call. But the admin team has agreed, that this is the right judgement at this time.

I'd been chewing this over and come to the same conclusion - there was nothing else you could do, for now, to avoid having to stay up every night containing wildfires. Let's just hope that no banned items are unequivocally discovered in the near future. Fingers crossed, eh?

Once again, Doug, thanks for everything - awkward decisions and all. We don't say it often enough.

Mars methane map made APOD.

Global map of methane release during martian summer available here: http://apod.nasa.gov/apod/image/0901/marsm...ne_nasa_big.jpg

Much of the known plumes seem to originate from the Arabia Terra region. Some of the areas with the least amount of methane include Hellas Planitia and Elysium Mons.

Hellas Planitia is a known area where most dust storms originate on Mars. So if dust storms have anything to do with production of methane, then you would have to explain the huge discrepancy in the amount of methane build up there.

Elysium Mons is a known volcanic region. So if volcanic activity has anything to do with the production, then likely that region is truly dead volcanically speaking. I would like to a map that includes Olympus Mons before forming an opinion on that.

Why over Arabia Terra? I think NASA has this correct. This tends to indicate subsurface sources for the methane that maybe unique to that area. What that is, we cannot be sure of yet.

If the source were photochemical, explain the distribution. I would think there would be a distribution bias horizontally over the equatorial latitudes instead of what we actually see. Perhaps it is because of ice reservoirs or perhaps something else.

The known distribution would be a problem for a lot of possible different explanations for the source. Let's face the fact that we need better methane maps. The need might suggest a dedicated mission of some sort!

Regardless, it is a fascinating mystery. I would think following the methane is now a good strategy; but we need the proper equipment and advanced planning to do the job properly. I would think changing the landing spot for MSL would be risky at this late stage, unless there are instruments that could easily be brought aboard to make it worth it. I have my doubts.

Doug, I support the decision because the rationale is sound, aside from admin workload. Most UMSFers love it here because above all it's a no-drama place where some extremely smart people freely share their ideas with us laymen, and preserving that feature of the forum is certainly a priority.

As Nigel said, we don't thank you & the admin team enough for this place, nor do we express our appreciation as often as we should for consistently keeping the standards high. If it was easy, anybody could do it; you guys aren't "anybodies". Thanks.

If you do Mars Google, I found the three regions to be about the same northern latitud. However, Syrtis and Nili Fossae are very close and Arabia Terra is about 3,000 kilometers west of the first ones.

The other thing, I have observed the methane distribution thru the APOD picture and found that the plumes are not uniformily distributed all planet but localized mostly in that zone. Is that methane distribution consistent in spite of the fact its intensity varies with the seasons.

These many questions might be solved with the future orbiters with adequate instruments to detect the methane. MSL will have it but it won't see all Mars. Hence, the Nili Fossae would be considered again as the one of the four potentials landings.

Sorry for this question from someone that does not understand these things very well.

When they say "parts per billion", what billions are they talking about, other atmosphere components?

Considering the thinness of Mars atmosphere, how would that translate to Earth's atmosphere?

Thanks in advance.

That is an EXCELLENT question.

It would imply one gram of stuff (methane) in a billion grams of other stuff (air).

Here is a more detailed article: http://en.wikipedia.org/wiki/Parts_per_notation

My favorite quote:
"it is not formally part of the International System of Units (SI).[2] Consequently, according to IUPAP, 'a continued source of annoyance to unit purists has been the continued use of percent, ppm, ppb, and ppt.'"

[I count myself among the 'annoyed': for most drug-like molecules, ppm is directly proportional to units molar (M). But if you are comparing with especially heavy or light molecules in the mix, this can throw off the relationship.]

-Mike

it seems someone else answered the question before I posted...

And I think I know why in this particular case it's easier to use ppb: volume will fluctuate at different pressures and temperatures.

Trying to sort out the volume at the particular temperature (which will vary widely on Mars) and pressure (big difference from Hellas Basin (1.155 kPa) to the top of Olympus Mons (0.03 kPa)) would make trying to calculate concentration of g (or moles) per volume a pain.

But I think the spectroscopic method gives units molar from Beer's law. A = cl: A is absorbance, c= concentration, l = path length.

-Mike

[Fun random trivia fact: the human nose can detect this molecule at 10 ppb on Earth at standard temperature and pressure (STP)]