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.
What silliness. Any organisms would have evolved for the specific environment of high salinity. The fact that “some” terrestrial organisms CAN live in these conditions (and given the teeming life around deep-sea “black smokers” where both the salinity and temperature are MUCH higher than regular sea-water, I don’t see any “salinity barrier” to life.
This report has nothing to do with the new Phoenix mission.
So the Earth lander landed near the Dead Sea and took samples back to Mars, where Martian scientists analyzed the water and said “Earth water is too salty to support life”.
The Red one? Not a guess, I'm going by the antennae.
Phoenix isn't the first to land, and its location was chosen where there is an ebb and flow of "ice".
"Mars' Water Appears To Have Been Too Salty To Support Life "
It's not supposed to be life as we know it. They're Martians, dummy.
yitbos
Oh, yeah, Martians...
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“The scientists say that the handful of terrestrial halophiles — species that can tolerate high salinity — descended from ancestors that first evolved in purer waters.”
How do they know this?
The oceans used to be much lower in salinity, probably fresh or bordering on it. Partly, though, there’s an assumption at work that, since most known lifeforms aren’t halophiles, the halophiles must have arisen from them (rather than the other way around). Eventually this may be settled one way or another by studies of deep sea vents and ocean floor sediments.
It’s not surprising that most species on Earth are not halophiles, since most of the Earth is not extremely salty. Many or most halophiles are classified in Archaea, a domain of life unto itself. It’s speculative to talk about their origins.
So where are these evolved Martian organisms? Oh, I know, the same place the lunar organisms are, the ones that evolved for living sans atmosphere. We know that terrestrial bacteria survived on some of our space vehicles.
Well, sans atmosphere also implies sans water. Any terrestrial bacteria that "survived" did by sporulating and going dormant, not by continuing to grow and propagate.
However, there are MANY types of bacteria that can survive in highly saline environments, and thrive and grow quite nicely, so your argument is fallacious--a case of comparing apples and oranges..
No it isn't. I asked for the location of these evolved Martian organisms. I then provided a tongue in cheek answer for their absence. The fact is, there are no Martian halophilic(or otherwise) organisms. I was pointing out your fairytale as such, a fairytale. The fact that earth organisms exist is no, repeat, no evidence of life of any type on Mars. That evidence has to be developed from purely Martian data. The writers pointed out that high concentrations of salt are inimical to the genesis of life and that high concentrations of salts are evident on Mars for billions of years in the past.
The researchers themselves placed this statement in the abstract for their article.
Our calculations indicate that the salinity of well-documented surface waters often exceeded levels tolerated by known terrestrial organisms.
If you reread CAREFULLY what I said, you will see that I never said anything about the existence of "Martian" halophile bacteria. What I said was that a strongly saline environment is no barrier to life. That being proven by the existence of such life in saline solutions as strong as any that might exist on Mars (i.e. saturated salt solutions). A saturated salt solution is the same on Mars as on earth. So your nutcase theory about "purely Martian data" is so much bullshit.
"Our calculations indicate that the salinity of well-documented surface waters often exceeded levels tolerated by known terrestrial organisms."
And I'm telling you that these "researchers" don't know their asses from holes in the ground. I've done work with research groups that worked with exactly such halophilic organisms.
For all we know, the original source of life on earth might well have been halophilic bacteria, living in hot springs deep inside the earth, well before conditions on the surface were such as to allow life.
Bullshit! I did read what you posted carefully and this is what you posted.
Any organisms would have evolved for the specific environment of high salinity.
Evolved means that the organisms were required to adapt to the evironment. The point of the article is that the organisms did not have an environment in which to spring into being abiotically. Show me the theory that has high levels of salinity as the starting environment for life. And any theory that I have heard of requiring salts also requires a gradient, IOW low concentrations are in the picture.
As for your belittling of the researchers, show us your peer reviewed paper on the subject.
I agree. The Mars Rovers have explored far less than 0.00001% of the Martian surface. To base general conclusions on what they have found and analyzed is absurd. Suppose Martin MASA (Martian Aeronautical and Space Administration), under the direction of Marvin the Martian, sent rovers to Earth and they landed in South East California near Mono Lake:
Tufas (Calcium Chloride salt crystal towers) near the shore of Mono Lake And analyzes the chemistry of the water and finds the salinity level is 8.1% with a highly alkaline pH of 10, large quantities of other chlorides, carbonates, and sulfides, fails to notice the Fairy Brine Shrimp that live quite happily in those severe conditions, and concludes that life is not possible on Earth.
That is a very unscientific statement. I would rephrase that to "So far, we have not found any Martian halophilic (or otherwise) organisms."
Lack of evidence for a thing is not evidence of lack of that thing. If I toss a needle into a haystack in a field of heystacks, and you spend two years sifting through the hay looking for the needle, the fact that you do not find it, is not proof that it isn't there. It's merely proof you haven't found a needle. Also, finding a needle in one haystack is not proof that there are needles in the other haystacks... only that it may be possible there are needles in the other haystacks.
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