[X] My Assistant

[Guest_AlexBlackwell_*]

Dig deeply to seek life on Mars
AGU Release No. 07-03
29 January 2007

This refers to the following paper, which was published online today in Geophysical Research Letters:

Dartnell, L. R.; Desorgher, L.; Ward, J. M.; Coates, A. J.
Modelling the surface and subsurface Martian radiation environment: Implications for astrobiology
Geophys. Res. Lett., Vol. 34, No. 2, L02207
10.1029/2006GL027494
30 January 2007
Abstract

[nprev]

Interesting. Wonder if degradation of near-surface organic compounds over time is also addressed by this paper. If there is in fact anything there (even down deep), you'd think that there would be detectable organic residue within our reach due to various regolith mixing processes (esp. in the polar areas), unless the radiation environment is just too severe for them to survive...

[ElkGroveDan]

Also at Space.com

Study: Surface of Mars Devoid of Life
By Ker Than

[Guest_AlexBlackwell_*]

Interesting. Wonder if degradation of near-surface organic compounds over time is also addressed by this paper.

After a quick skim, all I could see relating to organics was the brief excerpt from paragraph 3:

Solar UV rapidly deactivates unshielded cells [Cockell and Raven, 2004], and is also believed to have created highly oxidising surface conditions that destroy organic molecules in the topsoil. The Viking lander probes found no trace of organic compounds, not even at the level expected from meteoritic infall [Yen et al., 2000]. UV penetrates only millimetres into regolith [Cockell and Raven, 2004], but there is estimated to be around a meter's depth of loose topsoil [Soderblom et al., 2004] within a portion of which wind-mixing of oxidants is expected to present a serious biological hazard. Beyond the penetration depth of UV the ionising radiation of solar energetic protons (SEP) and galactic cosmic rays (GCR) dominate.

That the paper doesn't address organics in greater depth shouldn't be too surprising since its thrust is with the radiation environment, not the widely suspected near-surface oxidants.

[nprev]

True; always interesting to see a new set of contraints introduced to the problem, though. Thanks, Alex!

Looks like it's time to think about deep (>7m) core drilling experiments at least in order to differentiate between near-surface environmental effects & bulk regolith composition. This seems worth doing even if organics aren't the focus given the possible effects of hyper-oxidants on the terrain over time (esp. during transient moist conditions, if any).

[Guest_Zvezdichko_*]

That's why I raised the question about the penetrators. They can "dig themselves" at least two meters under the martian soil, then a drill may go even deeper. I'd like to see yet another Deep Space 2 mission.

[ustrax]

Monday bonus interview at spacEurope...

"If cells were only recently brought to the surface, such as in the gullies in crater walls that we’ve seen flow with liquid water in the last few years, then they could survive the radiation for long enough for us to sample them."

[nprev]

Food for thought indeed...

I wonder if MRO is capable of further refining our understanding of the frequency of these events (if that's what's really happening). What would be most desirable would be to find some sort of cyclic process area--ideally a periodic "eruptor" or two--that we could predict far enough in advance for a sort of a mini-MSL launch.

[ustrax]

Follow the water?...Follow the oil!

""Search for oil reservoirs on Mars" was the result of a deep study on the history of Mars, focused on the search for oil on the Red Planet, having into account that oil might be a reserve of organic material for potential life forms."

[tty]

I know we have at least one petroleum geologist on the forum, so perhaps it is unwise of me to sound off on the subject. However the whole premise sounds weird to me. Here on Earth oil is created from fossils (mostly marine, occasionally freshwater), so to find oil on Mars seems to me require that life and liquid water has existed there in the past, and on a fairly large scale too.

Oil creation also requires a fair amount (but not to much) heat, so I suppose the right place to search would be on the outskirts of the Tharsis bulge.

For oil to survive for any length of time also requires an impermeable caprock. I suppose ice would do quite well under martian conditions.

[nprev]

Mmm...I don't know if all possible hypotheses for petroleum formation have been completely ruled out yet, TTY. Last I heard on the subject there was still no firm consensus that oil is indeed a true fossil fuel...

[MarsIsImportant]

Mmm...I don't know if all possible hypotheses for petroleum formation have been completely ruled out yet, TTY. Last I heard on the subject there was still no firm consensus that oil is indeed a true fossil fuel...

That's true. Rumors have it that there are alternate origins for 'supposed' fossil fuels. It's hard to prove one way or the other. That's why a return sample from Titan is so important!

[edstrick]

The scientific consensus is as stong as in the "Evolution vs Intelligent Design" debate that petroleum <but not all hydrocarbons.. there are methane seeps from the mantle, apparently> is from biologic materials.

Tommy Gold, the chief proponant of the primordial mantle origin theory, was a fine physicist, but no geochemist or organic chemist and was always able to ignore evidence from outside his areas of interest, while cherry-picking evidence that supported his theories. When he was right, he was very very right, but he was often wildly and "crankishly" wrong.

[nprev]

Gotcha, Ed; thanks for the clarification. Given all that, though, any Martian hydrocarbons found still wouldn't constitute definitive proof of past life in my opinion, unless perhaps there were well-evolved bugs thriving in the mix. Petroleum is an extremely complex substance, so I doubt that Mars "oil" would be a close chemical match in many important respects.

Still, who really knows? Let's go drillin' & find out!

[Mizar]

ustrax, you said:
"Follow the water?...Follow the oil! "

I say:
Follow the abyss !

Here you go

http://news.bbc.co.uk/2/hi/science/nature/6461201.stm

And here:

http://www.nature.com/news/2007/070312/full/070312-11.html