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Update on Mars' atmosphere, Media briefing on NASA Jan 15th
Juramike
post Jan 21 2009, 05:23 PM
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I'm speculating here, (and I haven't yet read the papers posted above), but to get the photochemical reduction of methane from CO2 would require a wet catalyst. The water acting as the hydrogen source. So you'd need wet (or icy) dust grains, probably airborne condensation nuclei in the clouds.

But dust grains in the atmosphere are highly oxidizing. How easy is it to do a photochemical reduction on (or in the presence of) an oxidizing surface?

At first glance, it seems kinda tough...


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stevesliva
post Jan 21 2009, 05:39 PM
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QUOTE (centsworth_II @ Jan 21 2009, 11:49 AM) *
And we wonder why the popular press can't get it right.

http://blogs.discovermagazine.com/badastro...ane-media-mess/
He points out that the press release was titled "Discovery of Methane Reveals Mars is not a Dead Planet"

Just sayin...
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silylene
post Jan 21 2009, 06:23 PM
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QUOTE (Juramike @ Jan 21 2009, 06:23 PM) *
I'm speculating here, (and I haven't yet read the papers posted above), but to get the photochemical reduction of methane from CO2 would require a wet catalyst. The water acting as the hydrogen source. So you'd need wet (or icy) dust grains, probably airborne condensation nuclei in the clouds.

But dust grains in the atmosphere are highly oxidizing. How easy is it to do a photochemical reduction on (or in the presence of) an oxidizing surface?

At first glance, it seems kinda tough...



Agreed. I think it would require non-oxidizing metal oxide surfaces, such as the grains in clays, and water vapor (morning frosts?). But as we know, large parts of the Martian surface are coated with highly oxidized dusts (superoxides, peroxides, chlorates). We need to know which parts of the martian surface are not dusted with dusts whose surfaces is highly oxidized.
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marswalker
post Jan 22 2009, 04:45 PM
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QUOTE (centsworth_II @ Jan 20 2009, 12:37 AM) *
The dynamic event could involve the water release only. Once released, the water is involved in a surface process that produces the methane. But, as I said, I'll be happy to have surface production proved wrong.



The mechanism for converting iron oxide, C02 and water into methane require heat. A theory was that some sort of leftover volcanic heat is doing the cooking, allowing the chemistry to make methane. The problem with that theory is we've never witnessed any sort of volcanic activity on Mars - only the long-dead results of volcanism remain.

So PCHEM processes are being looked at as a possible source, but there seems to be a very good chance that it's from biological processes.


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marswalker
post Jan 22 2009, 04:50 PM
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QUOTE (stevesliva @ Jan 21 2009, 09:39 AM) *
http://blogs.discovermagazine.com/badastro...ane-media-mess/
He points out that the press release was titled "Discovery of Methane Reveals Mars is not a Dead Planet"

Just sayin...



smile.gif And his reference about "dead planet" includes both geological as well as biological definitions. If it's not biologically "alive", it must be geologically "alive", or there wouldn't be active ongoing processes which end in methane production.


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centsworth_II
post Jan 22 2009, 09:02 PM
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QUOTE (marswalker @ Jan 22 2009, 11:45 AM) *
The mechanism for converting iron oxide, C02 and water into methane require heat.

That's the geochemical method. I was proposing that released water would be available for photochemical production of methane. (The forgotten reaction)

QUOTE (marswalker @ Jan 22 2009, 11:50 AM) *
If it's not biologically "alive", it must be geologically "alive", or there wouldn't be active ongoing processes which end in methane production.

Once again, what about photochemical production? Would that rate calling Mars "alive"?
(Of course, Mars is "alive" to many of us already, no matter what is found in the future.) biggrin.gif
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Vultur
post Jan 23 2009, 08:11 AM
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QUOTE (marswalker @ Jan 22 2009, 04:50 PM) *
smile.gif And his reference about "dead planet" includes both geological as well as biological definitions. If it's not biologically "alive", it must be geologically "alive", or there wouldn't be active ongoing processes which end in methane production.


True. It sounds ambiguous, and I think it's meant to be. I've seen a 'dead' or 'geologically dead planet' (or moon) used to mean one which has no volcanism (like Mercury or our Moon).
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Juramike
post Jan 23 2009, 02:10 PM
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QUOTE (Juramike @ Jan 20 2009, 08:00 AM) *
Could a network of upward pointing LIDARs be used for detection of methane absorption bands? Then you'd get cloud/precip data while waiting around for the ground to burp.


Poking around, it might be possible to use an orbiting downward LIDAR to get localization of trace gas data.
Found this abstract:

Riris et al. AGU Abstract#P51C-212. "Mars Trace Gas Detection with a Remote-Sensing LIDAR". (Abstract here)

From the abstract:
"The small laser footprint and the resulting high spatial resolution, will also allow the identification biologically and geologically active sites for a future landing missions."

-Mike


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silylene
post Jan 23 2009, 03:42 PM
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This is an interesting idea. I wonder how much power the laser would require, in order to generate a significant enough scattering signal to be observed from orbit with good S/N? Also, what's the vertical resolution? And would this just work during the martian night, for that wavelength? (I am guessing it might work better then; but if so, it would require on some type of on board energy storage system, such as batteries)
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tty
post Jan 24 2009, 12:12 AM
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QUOTE (marswalker @ Jan 22 2009, 05:45 PM) *
The problem with that theory is we've never witnessed any sort of volcanic activity on Mars - only the long-dead results of volcanism remain.


Given the almost complete absence of impact craters on some of the Tharsis volcanoes volcanic activity certainly continued until fairly recently (geologically speaking). Here on Earth some active volcanoes have dormancy periods that run into tens of thousands of years, so the fact that we have seen no activity in a few decades is hardly conclusive.
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scalbers
post Dec 22 2013, 05:26 PM
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QUOTE (silylene @ Jan 23 2009, 04:42 PM) *
This is an interesting idea. I wonder how much power the laser would require, in order to generate a significant enough scattering signal to be observed from orbit with good S/N? Also, what's the vertical resolution? And would this just work during the martian night, for that wavelength? (I am guessing it might work better then; but if so, it would require on some type of on board energy storage system, such as batteries)


Here is a Mars orbiting LIDAR proposal...

http://www.lpi.usra.edu/meetings/marsconce...12/pdf/4202.pdf



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TheAnt
post Dec 24 2013, 11:40 AM
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QUOTE (tty @ Jan 24 2009, 01:12 AM) *
Given the almost complete absence of impact craters on some of the Tharsis volcanoes volcanic activity certainly continued until fairly recently (geologically speaking). Here on Earth some active volcanoes have dormancy periods that run into tens of thousands of years, so the fact that we have seen no activity in a few decades is hardly conclusive.


Oh yes that's true though there are some craters to be found, IIRC the planetary scientists do think the timespan is quite long like millions of years between each eruption. So we better do not hold our breath in anticipation for the next one. wink.gif

Then again, if we'd see one in the future, it might be interesting not just for the drama, it might even affect martian climate and perhaps surface missions to some degree (dust) and with such a thin atmosphere to start with perhaps even a slight change in pressure.

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