Meteor study pours cold water on warm Mars theory

WASHINGTON (Reuters) – A study of meteorites chipped off
the surface of Mars suggests the planet has been frozen for 4
billion years and probably never had the warm wet conditions
that could have given rise to life, two researchers said on
Thursday.

Their study of two meteorites that fell to Earth suggests
they were never in warm conditions. The report, published in
the journal Science, contradicts theories the now-frozen planet
may once have been warm enough for life to have arisen.

“First, we evaluated what the meteorites could have
experienced during ejection from Mars, 11 to 15 million years
ago, in order to set an upper limit on the temperatures in a
worst-case scenario for shock-heating,” said Benjamin Weiss, an
assistant professor at the Massachusetts Institute of
Technology. He did the work while a graduate student at the
California Institute of Technology.

They concluded the two meteorites were unlikely to have
been above the boiling point of water during their ejection
from the martian surface 11 million years ago.

Then Weiss and fellow student David Shuster measured the
amount of argon remaining in the samples.

Argon, a gas, is known to leak out of rocks at a rate that
depends on temperature.

The cooler the rock has been, the more argon will have been
retained.

“The small amount of argon loss that has apparently taken
place in these meteorites is remarkable. Any way we look at it,
these rocks have been cold for a very long time,” Shuster said
in a statement.

Their calculations suggest the Martian surface has been
frozen for most of the past 4 billion years.

“On Earth, you couldn’t find a single rock that has been
below even room temperature for that long,” Shuster said.

That does not mean that rovers looking for evidence of warm
springs, lakes or seeps on Mars are wasting their time.
Geothermal activity below the surface could have created small
areas that could harbor life.

“Our research doesn’t mean that there weren’t pockets of
isolated water in geothermal springs for long periods of time,
but suggests instead that there haven’t been large areas of
free-standing water for 4 billion years,” Shuster said.

“Our results seem to imply that surface features indicating
the presence and flow of liquid water formed over relatively
short time periods,” Shuster said.