Mars too Salty for Life?, The end of the dream? Options

[abalone]

http://www.abc.net.au/news/stories/2008/02/16/2164485.htm
http://cosmiclog.msnbc.msn.com/archive/200.../15/668749.aspx

[djellison]

and http://marsrovers.jpl.nasa.gov/newsroom/pr.../20080215a.html

[nprev]

All the more reason to search aggressively for any signs of past or present life; we need to understand constraints (and extinction factors, if applicable) as well as possible.

[JRehling]

I used to eat a lot of salt and vinegar potato chips and I'm still alive.

Of course, Opportunity is only showing us one niche in the martian history. If there was a global sea, it would have uniform salinity and acidity, but otherwise, perhaps different basins would have different chemistry.

[nprev]

Yeah, I was actually thinking something very like that too, JR. Mars may well have been a bewildering patchwork of microclimes in its infancy, much more so than the Earth has been throughout its history due to the persistent ocean cover. Think it's going to be quite awhile before we can reconstruct the entire story...if ever.

[brellis]

99 days till Phoenix lands - maybe she'll show us something different.

[nprev]

I'm confident enough to say yes, if for no other reason that the terrain gets buried under CO2 snow (undoubtedly with some H2O clathrates) every year; there's gotta be some ongoing chemical alteration of the upper regolith. Suspect that we won't see shallow salty layers like we have @ Gusev, though hard to verify that prediction without mobility.

[dburt]

...Opportunity is only showing us one niche in the martian history. If there was a global sea, it would have uniform salinity and acidity, but otherwise, perhaps different basins would have different chemistry.

Agree about one specific niche, but it need not be an especially rare one. Five Mars surface landers, dating back to Viking, all detected abundant salts, on different areas of Mars. The highest levels may have been measured by the two rovers, but there seem to be on the order of 10% sulfate salts nearly everywhere on the dusty surface, judging from measurements made by the other three landers (and more recently, from orbit). You might not even need seas or sedimentary basins, because on any water-rich terrestrial planet where the vast majority of the water is frozen, frozen-out crystalline salts should be abundant. (Compare also Europa.) Surface evaporation of concentrated brines, "wicking" (capillarity-driven salt efflorescence) involving moisture, and sublimation of ice layers that once covered brines, probably also contributed to the surface saltiness. Impacts and the wind probably served to distribute the salts planetwide, as well as (in the case of impacts) to generate ferric acid sulfates (e.g., jarosite), although Roger Burns-type moist weathering of pulverized sulfides would also serve. Millenia of frost leaching of salts with the largest freezing point depressions (i.e., chlorides), should have left the surface enriched in those salts with the least F.P. depression (i.e., sulfates), whether or not minor quantities of sulfates were also added to the surface by later volcanism. On a basaltic planet, especially one with migrating wind-driven basaltic sands and pulverized basaltic regolith, acidic seas or lakes are extremely unlikely, as is acidic groundwater, a Chemistry 101 fact that I keep repeating (and that Roger Burns knew well). The only way acids should be able to persist on basaltic Mars is in a frozen or crystalline state (e.g., trapped in ferric acid sufates like jarosite, as Roger Burns first proposed). Paul Knauth and I published on Mars surface saltiness (sulfates vs. chlorides) well before the rovers landed (in 2002 in Icarus and in 2003 in JGR), and I recently reviewed these ideas for participants at the LPI Martian Gullies Workshop in Houston.

As a general comment, I'm not aware that the cross-bedded salty rocks at Meridiani have ever been named "evaporites" except by a few posters to this site. More precision in terminology might be appropriate.

-- HDP Don

[mike]

Mars too salty for life as we know it, maybe..

[abalone]

Mars too salty for life as we know it, maybe..

Yes....but then Venus is too hot for life as we know it and Titan is too cold for life as we know it. I'm not advocating we give up hope. No one would be more pleased than me if the right niche for life on Mars exists or once did, but if I were a bookmaker I might be altering the odds I offer on any bets.

There has been a bit of "wanting to believe" despite mounting evidence against.

[Bill Harris]

Balderdash. Life always has a way. On Earth we have it in hot oceanic smokers and in evaporitic desert playas and there are acidophiles and sulfate bacteria and other extremophilic bacteria.

--Bill

[ugordan]

Yes, but did life actually begin in such extreme environments? It's one thing for it to adapt to an extreme environment, it's another to actually develop there.

[Stu]

Here in the UK the BBC is announcing this as "The death knell for boffins' hopes of finding life on Mars" but I'm with you, Bill, this isn't the end of the story, not by a loooooooooooooooooooooooooooong way. These are just results from two tinier than tiny areas of Mars, and there are places on Mars where conditions would have been radically different, I'm sure.

I'm taking this news with... ahem... a pinch of salt.

[abalone]

I feel a theory coming on...
Maybe high acid on Mars is the norm for all smaller planetary object at a distance from their stars where the metal concentration drops off and the concentration of volatiles increases. Not enough iron to bind and sequester sulfur into the core as sulfide. Thats what makes the Earth habitable its massive iron core.

Europa, Io and Titan even if they were warm enough would be sulfuric acid hell holes incapable of sustaining life. There seems to be enough indications on Europa for sulfuric acid, its just a giant tank of battery acid under that icy crust.

Maybe the habitable zone around a star not only relies on temperature but also on the iron/sulfur ratio being above a certain threshold, the further out you go the more acidic the planetary bodies become.

[Juramike]

Maybe the habitable zone around a star not only relies on temperature but also on the iron/sulfur ratio being above a certain threshold, the further out you go the more acidic the planetary bodies become.

Ammonia, as well as many heterocyclic nitrogen compounds are actually basic. I'd expect anything with a larger amount of ammonia ices (outer solar system bodies that fomed beyond the ice limit) might be basic.

["base" in this sense = materials that suck up protons when dissolved in water, shifting the water equilibrium to favor hydroxyl ions (-OH) in solution, raising the pH and making the solution more alkaline].

-Mike