Posted on 05/30/2008 1:35:19 AM PDT by LibWhacker
ScienceDaily (May 30, 2008) — A new analysis of the Martian rock that gave hints of water on the Red Planet -- and, therefore, optimism about the prospect of life -- now suggests the water was more likely a thick brine, far too salty to support life as we know it.
The finding, by scientists at Harvard University and Stony Brook University, is detailed May 30 in the journal Science.
"Liquid water is required by all species on Earth and we've assumed that water is the very least that would be necessary for life on Mars," says Nicholas J. Tosca, a postdoctoral researcher in Harvard's Department of Organismic and Evolutionary Biology. "However, to really assess Mars' habitability we need to consider the properties of its water. Not all of Earth's waters are able to support life, and the limits of terrestrial life are sharply defined by water's temperature, acidity, and salinity."
Together with co-authors Andrew H. Knoll and Scott M. McLennan, Tosca analyzed salt deposits in four-billion-year-old Martian rock explored by NASA's Mars Exploration Rover, Opportunity, and by orbiting spacecraft. It was the Mars Rover whose reports back to Earth stoked excitement over water on the ancient surface of the Red Planet.
The new analysis suggests that even billions of years ago, when there was unquestionably some water on Mars, its salinity commonly exceeded the levels in which terrestrial life can arise, survive, or thrive.
"Our sense has been that while Mars is a lousy environment for supporting life today, long ago it might have more closely resembled Earth," says Knoll, Fisher Professor of Natural Sciences and professor of Earth and planetary sciences at Harvard. "But this result suggests quite strongly that even as long as four billion years ago, the surface of Mars would have been challenging for life. No matter how far back we peer into Mars' history, we may never see a point at which the planet really looked like Earth."
Tosca, Knoll, and McLennan studied mineral deposits in Martian rock to calculate the "water activity" of the water that once existed on Mars. Water activity is a quantity affected by how much solute is dissolved in water; since water molecules continuously adhere to and surround solute molecules, water activity reflects the amount of water that remains available for biological processes.
The water activity of pure water is 1.0, where all of its molecules are unaffected by dissolved solute and free to mediate biological processes. Terrestrial seawater has a water activity of 0.98. Decades of research, largely from the food industry, have shown that few known organisms can grow when water activity falls below 0.9, and very few can survive below 0.85.
Based on the chemical composition of salts that precipitated out of ancient Martian waters, Tosca and his colleagues project that the water activity of Martian water was at most 0.78 to 0.86, and quite possibly reaching below 0.5 as evaporation continued to concentrate the brines, making it an environment uninhabitable by terrestrial species.
"This doesn't rule out life forms of a type we've never encountered," Knoll says, "but life that could originate and persist in such a salty setting would require biochemistry distinct from any known among even the most robust halophiles on Earth."
The scientists say that the handful of terrestrial halophiles -- species that can tolerate high salinity -- descended from ancestors that first evolved in purer waters. Based on what we know about Earth, they say that it's difficult to imagine life arising in acidic, oxidizing brines like those inferred for ancient Mars.
"People have known for hundreds of years that salt prevents microbial growth," Tosca says. "It's why meat was salted in the days before refrigeration."
Tosca and Knoll say it's possible there may have been more dilute waters earlier in Mars' history, or elsewhere on the planet. However, the area whose rocks they studied -- called Meridiani Planum -- is believed, based on Mars Rover data, to have been one of the wetter, more hospitable areas of ancient Mars.
Tosca, Knoll, and McLennan's work was supported by NASA and the Harvard Origins of Life Project.
If we had to drink sea water we’d be snaffed too; the good news is that it rains occasionally and we can drink from rivers and lakes. Ancient Martians would certainly have figured that out as well. Reminds me of Santino Corleone asking Michael if he went to college for four years to get stupid...
But what about Uranus? Is that salty too?
Dunaliella Salina a type of Algae lives in salt fields.
http://en.wikipedia.org/wiki/Dunaliella_salina
*
Totally narrow, almost fraudulent conclusion.
I can drink water from lake Erie.
I can drink water from the Pacific ocean, just not too much.
I can drink water from an oasis in the middle of the Sahara.
There are places in Nevada that if I drank water from a hole in the ground, I’d be dead in 48 hours.
There are brine shrimp on the planet that live in water so corrosive it would probably burn a hole in your shirt.
But it is interesting we are getting some results back.
There are thermophiles, never heard of halophiles!
(salt loving)
I’m gonna make popcorn.
Well, they say they have found Martian rocks in Antarctica. And if those rocks can get here, good chance ours can get there.
And there are few - very few places on Earth that if you pick up a rock, it doesn’t at least have some bacteria in it.
My guess would be the chances of Mars being devoid of life are exceedingly remote.
There are plenty of algae and lichens and fungi that would do very well on Mars, thank you.
Yet another “life on another planet” theory wrecked.
Riiiight.
True. It is hard to believe a scientist could come to such a conclusion. "Some rocks are too salty therefore all rocks are too salty."
Have you ever been abducted by aliens?
Have faith, Vlad! John Carter's battles at the side of Tars Tarkas prove that there is life on Barsoom!
Lick it and find out. ;-)
God created it all, and there is only one Earth, and man is created in His image and every attempt to prove otherwise just continues to support that which we see by faith.
Hmmmm....o-k-a-y.
Happy Friday, Kolokotronis, warp factor 9 to the weekend!
Only when I eat pretzels...
“Hmmmm....o-k-a-y.
Happy Friday, Kolokotronis, warp factor 9 to the weekend!”
Didn’t have a misspent youth reading Edgar Rice Burroughs eh?
Off to the salt mine, then go pay for next winter’s wood pellets and then to the cottage for the weekend. Life can be so complex at times!
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.