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Early Mars Maybe Not So Wet
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[تصویر:  13473086971.jpg]



Early Mars may not have been as warm or wet as scientists suspect, a
finding which could impact the likelihood that the Red Planet was
capable of evolving life at the time when it was getting started on
Earth.




A new study presents an alternative explanation for the prevalence of
Mars' ancient clay minerals, which on Earth most often result from
water chemically reacting with rock over long periods of time. The
process is believed to be a starting point for life.




The clays, also known as phyllosilocates, are among the strongest
pieces of evidence for a Mars that once was warmer, wetter and much more
like Earth than the cold, dry, acidic desert which appears today.


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Data collected by orbiting spacecraft show Mars' clay minerals may
instead trace their origin to water-rich volcanic magma, similar to how
clays formed on the Mururoa atoll in French Polynesia and in the Parana
basin in Brazil. That process doesn't need standing bodies of liquid
water.




"The infrared spectra we got in the lab (on Mururoa clays) using a
reflected beam are astonishingly similar to that obtained on Mars by the
orbiters," lead researcher Alain Meunier, with the University of
Poitiers in France, wrote in an email to Discovery News.




The team also points out that some of the Mars meteorites recovered
on Earth do not have a chemistry history that supports standing liquid
water.


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But even if Mars was not as warm or wet as scientists have theorized, that doesn't close the door on the possibility of life
The clays, for example, could have still hosted the early chemical
reactions for life, even if they did not themselves form from standing
bodies of water.




"On Earth, we think clay minerals were pretty important in the origin
of life because the structure of them and the water they hold and the
elements that are within them seem to be good things to develop RNA and
we get to DNA from that," planetary scientist Brian Hynek, with the
University of Colorado at Boulder, told Discovery News.



"Since we find clays all over Mars from the same time period, it's
been thought that these are important for the question of habitability,
and they certainly are. But the clays are just one piece of the puzzle,"
he said.


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For example, the fingerprints of water have been found in other
minerals on Mars, though that water seems to have been more acidic.




"That's a challenge for life, but we certainly have a lot of examples
of life living in very acidic places on Earth," Hynek said.




The first direct measurements of clay minerals on Mars are expected
soon. NASA's Opportunity rover is making its way to suspected clays on
the rim of a crater, while on the other side of the planet the roving
chemistry lab Curiosity is beginning a two-year mission that will head
to Martian clays near the foot of a mountain next year.
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