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

[Guest_PhilCo126_*]

Well, there's something called extremophiles...
An extremophile is an organism adapted to living in physically or geochemically extreme conditions.

[nprev]

Think the core issue is whether life could have ever evolved on Mars given the salty surface, and my argument is twofold:

1. Do current conditions reflect conditions in the distant past? (I doubt it.)

2. Is there only one golden biochemical pathway to the evolution of life? (I doubt that, too.)

[centsworth_II]

Keep in mind, we still don't know how life arose on Earth, let alone
how or under what circumstances it may have arisen on Mars. I've
seen ideas expressing that life may have started on clay surfaces,
in sea foam, on -- or in -- ice crystals and who knows how else. I
expect one day to read that life may have started in fluid-filled
cavities within salt crystals!

[Stu]

Well, I've had salt on my chips for years, and I'm fine...

Seriously tho, we just don't know, do we? This "Life was impossible because Mars was salty" extrapolation is based on observations of just two tiny locales. Very premature to doom the idea of martians to the history or science fiction books.

Come on Phoenix, surperise and delight us...!

[nprev]

Centsworth, that's an excellent point. The only thing we probably know about the origin of life on Earth is that it happened in one way due to the overall biochemical similarity between all extant organisms...and even that's open to debate, since it's possible that our particular flavor of life just won out over competitors.

Mars...who knows if, or what, or how? That's why we're looking.

[dburt]

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...
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.

Actually, what neutralizes S-rich acid is not iron (iron sulfides oxidize to highly acid iron sulfates, after all), but stronger bases such as soda (Na2O), lime (CaO), and magnesia (MgO), abundant mainly in silicate rocks such as basalt. It doesn't matter how much oxidized, acid sulfur (H2SO4, sulfuric acid) or chlorine (HCl, hydrochloric acid) was emitted, what matters is that there was enough silicate rock to neutralize the acid, producing neutral salts, such as gypsum (CaSO4*2H2O) or halite (NaCl). This is how most salts on early Earth were formed, shortly after acid degassing, and it is how most salts on early Mars were likewise produced. Earth's oceans remain relatively basic owing mainly to interactions of seawater with the basalt that makes up the sea floor, despite all of the acids that volcanoes and our civilization constantly emit into the atmosphere. In short: salty yes, acid no.

I don't see why some people expect Mars to be so different, if liquid water was present. As Knauth and I have stated in print, the ferric acid sulfates on the surface of Mars (both rover sites) probably indicate dry, cold, and salty, not warm, wet, and acid. Planets do get more volatile-rich as you go out from the sun, but these volatiles are not necessarily acid species (e.g., ammonia in the gas giants, as someone else pointed out). Note that I am not commenting on oxidation state, only acidity (although the two variables can be related), because both Earth and Mars appear to have oxidized surfaces (probably for different reasons - photosynthesis on Earth, UV radiation and hydrogen loss on Mars). I'm also not commenting on whether or not Mars has or had life, because I don't know the answer.

BTW, in 2001 I asked the late Graham Ryder of LPI what he thought at a party, and I really liked his reply: "Where are the shopping centers?" That was his droll British way of pointing that any life on Mars seems to have kept a pretty low profile. Note: his special interest was lunar geology, particularly regarding the LHB (late heavy bombardment, or lunar cataclysm, as it was also called).

-- HDP Don

[Shaka]

Even as we speak, Oppy is parked 473 meters above the Starbucks in the *Meridiani MegaMall*.

*Open until 10. Unlimited free parking

[JRehling]

That's not to dis all expert scientific opinion, but when there are so many open-ended variables, I find it hard to accept blanket pronouncements like this.

Those are some classic failed predictions, and there are many more (which I always enjoy reading), but then we could probably generate some pretty solid blanket pronouncements, too. Things about time travel, putting a galaxy into your pocket, kids listening to their parents' wisdom, people acquiring Superman-like powers, bacteria that thrive at the center of the Sun, etc. The whole domain of post-reviewing futurology is skewed by the fact that you only have the examples of the "never" statements that were proven wrong. The ones that actually WILL hold up forever can always be nonfalsifiably rebutted with a "...yet."

Still, this looks like shaky ground for the experts. Aside from the existence proof of terrestrial life, we don't know much about the parameters of what is possible, biologically, and what is not.

[nprev]

Aside from the existence proof of terrestrial life, we don't know much about the parameters of what is possible, biologically, and what is not.

JR, I'd take that one step farther and say that we know virtually nothing. One sample does not a continuum make.

If the "Pluto is/is not a planet" debate taught us anything useful by way of analogies, it's that natural things exist along contiuua, thereby complicating time-driven processes & our ability to assign labels to things. The only truly discrete objects are subatomic particles, the building blocks; variation to some degree exists at any higher order of organization.

(This might make a decent thesis topic for anybody out there looking to finish their MS, BTW; introducing some mathematical/statistical rigor into that proposition in order to prove or disprove it... )

[ElkGroveDan]

... but then we could probably generate some pretty solid blanket pronouncements, too..... putting a galaxy into your pocket

That one has been done already .

[Aussie]

Truly when we cannot seem to agree on a definition of what constitutes life, it is pretty arrogant to think that we can identify it, or indeed exclude it. I'm with Nprev, the probabilities remain within acceptable limits.

[Juramike]

Truly when we cannot seem to agree on a definition of what constitutes life, it is pretty arrogant to think that we can identify it, or indeed exclude it.

...And arrogant as well to think we can easily detect it.

Somewhere around in this forum was a link to a NASA study of life and the potential chemical pathways for life in exobiotic environments. [EDIT: link to article found in post 184, thread "The Surface Chemistry of Titan, link here]

The bottom line is: never say never.

A safe statement regarding the brine study on Mars would be that "the putative past environments on Mars might be difficult for many of the currently known microbes."

But as we are quickly learning, we know less about Life on Earth than we thought. Craig Ventner's recent genetic bioprospecting voyages around the globe's oceans have uncovered a huge genetic diversity previously unknown.

Here is one interview: http://www.nrdc.org/OnEarth/06sum/frontlines2.asp
(There was also a recently produced show on the Science channel that covered this voyage - definitely a must-view.)

A better statistic would be to figure how many of the currently known microbes on Earth could have survived in the past environments on Mars. Even if the answer is only one microbe species, it strengthens the claim that life could and still exists on Mars.

Since absence of evidence is not evidence of absence, proving that (microbial) life DOESN'T or DIDN'T exist on Mars will be very difficult.

-Mike

[Greg Hullender]

It's always hard to do meaningful statistics from a single data point. :-)

Personally, I think the most encouraging evidence for life on other worlds is that fact that it got started here so fast. Once the place had liquid oceans, pretty much, life appeared. That suggests it's pretty likely to appear again, given similar circumstances. (Claims that life came from outer space, I don't take seriously.)

On the other hand, the fact the multicellular life didn't arise until about 650 million years ago, suggests that that really is rare -- possibly unique. It boggles the mind that for over three billion years, the Earth had an oxygen atmosphere, but no plants and no animals -- just bacteria and mats of algae. in the oceans.

Anyway, like I said, reasoning from one data point is always hazardous. But I sure wouldn't bet on finding anything above the level of bacteria. On ANY world but this one.

--Greg

[AndyG]

Personally, I think the most encouraging evidence for life on other worlds is that fact that it got started here so fast. Once the place had liquid oceans, pretty much, life appeared.

All the more impressive given the Late Heavy Bombardment, perhaps 100atm of hot gas above the microbes' heads, and tides magnitudes higher than the ones we're used to. Hadean indeed.

On the other hand, the fact the multicellular life didn't arise until about 650 million years ago, suggests that that really is rare -- possibly unique. It boggles the mind that for over three billion years, the Earth had an oxygen atmosphere, but no plants and no animals -- just bacteria and mats of algae. in the oceans.

Multicellularism goes back a little further, and oxygen levels, while rising, are really quite low until around that point. Surely that's a link? Plentiful oxygen is required for increasing metabolic rates? That it took Deep Time for tectonics and life to get into a cycle where this could occur, and for the anaerobes to poison themselves off, isn't an issue for any world (ok, any world in a stable orbit within the HZ, perhaps with a stabilising moon) orbiting a star cooler than, say F5-ish - and there's got to be around 10^21 of those in the universe.

I would be startled if multicellular life occured just once out of a number that large.

Andy

[centsworth_II]

The 3 or 4 billion year span from single cell to
multi-cell organisms may not indicate slim chances
of that advance occurring. It may be more a result
of frequent hits by killer asteroids which kept viable
life on Earth at the most rudimentary levels.

The same conditions would most likely occur in any
developing planetary system. But my point is that
the change from single to multicellular life may be
a simple, inevitable step which just needs to wait
for the right moment to occur. This is different from
thinking that it is an unlikely step in the first place.

IMO, anyway.