WASHINGTON (AP) — Water percolating through the soil once
created a friendly environment that would have been ideal for life
to flourish on Mars, NASA scientists say.

It is not known how long this environment lasted or if any
organism actually developed. But scientists directing robot rovers
prowling the Martian surface said yesterday the evidence now is
clear that some rocks “were once soaked with liquid
water.”

“The ground would have been suitable for life,” said
Steve Squyres of Cornell University, the lead investigator for
science instruments on the rover Opportunity. “That
doesn’t mean life was there. We don’t know
that.”

Mars now is cold and dry and there is no apparent evidence of
life on its barren surface.

But Squyres said chemical and geological clues gathered by
Opportunity give dramatic proof that at some time in its past,
liquid water coursed over the rocks and soils.

Such conditions on Earth, Squyres said at a news conference,
“would be capable of supporting life.

“We believe that that place on Mars for some period of
time was a habitable environment,” he said.

Squyres said it is not known how long the life-environment
lasted, if the water collected in surface pools or underground, and
when in the long history of Mars the liquid water existed. Answers
to those questions, he said, probably will require missions that
scoop up Martian samples and bring them to laboratories on
Earth.

NASA researchers from the Jet Propulsion Laboratory in Pasadena,
Calif., who are guiding the exploration of Mars by Opportunity and
its twin, Spirit, said the primary goal of the rover mission was to
find evidence of Martian water.

That goal was accomplished, they said yesterday, when
Opportunity used all of its instruments to study a fine, layered
rock called El Capitan. The rock is embedded in the wall of the
crater where the six-wheeled robot began its journey on Mars.

“We’ve been attacking that outcrop with everything
we have,” said Squyres. The payoff is chemical and geological
evidence of a water history at that one spot.

Benton C. Clark III, a Lockheed Martin Space Systems scientist
and a member of the rover team, said that when Opportunity used an
abrasion tool to bore into the rock it found “an astounding
amount of salt” crystalized inside.

“The only way you can form such large concentrations of
salt is dissolve it in water and allow the water to
evaporate,” Clark said.

Clark said the salts may have been dissolved in water and then
crystalized as the water evaporated. Salts of bromine and chlorine,
he said, are deposited in patterned layers that match the
evaporation sequence found on Earth when briny water pools dry
up.

The scientists also found what they call
“blueberries,” small, globular-shaped inclusions in the
rock that can be formed by water. The inclusions are rather like
blueberries in a muffin, hence the name.

Some of the spherical objects have rolled into a small basin,
called the “blueberry bowl” by scientists, and will be
analyzed further by Opportunity to confirm their water origin.

Images also show voids the size of pennies randomly distributed
in the martian rocks. Such voids, called vugs, are often formed in
rocks on Earth when chemicals crystalize and then erode away,
leaving behind an empty space.

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