[meteorite-list] Martian Find Raises Chances of Life

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed, 6 Dec 2006 09:11:15 -0800 (PST)
Message-ID: <200612061711.JAA23110_at_zagami.jpl.nasa.gov>

http://www.thestar.com/NASApp/cs/ContentServer?pagename=thestar/Layout/Article_Type1&c=Article&cid=1165406828171&call_pageid=968332188492

Martian find raises chances of life
ALICIA CHANG
ASSOCIATED PRESS
December 6, 2006

LOS ANGELES - A provocative new study of photographs taken from orbit
suggests that liquid water flowed on the surface of Mars as recently as
several years ago, raising the possibility that the Red Planet could
harbour an environment favourable to life.

The crisp images taken by the Mars Global Surveyor do not directly show
water. Rather, they show apparently recent changes in surface features
that provide the strongest evidence yet that water even now sometimes
flows on the dusty, frigid world. Water and a stable heat source are
considered keys for life to emerge.

Until now, the question of liquid water has focused on ancient Mars, and
on the Martian north pole, where water ice has been detected. Scientists
have long noted Martian features that appear to have been scoured by
water or look like shorelines, and have tried to prove that the Red
Planet had liquid water eons ago.

"This underscores the importance of searching for life on Mars, either
present or past," said Bruce Jakosky, an astrobiologist at the
University of Colorado at Boulder, who had no role in the study. "It's
one more reason to think that life could be there.''

The new findings were published Wednesday in the journal Science and
NASA scheduled a news conference for Wednesday afternoon to announce the
results.

Oded Aharonson, an assistant professor of planetary science at the
California Institute of Technology, said that while the interpretation
of recent water activity on Mars was "compelling," it's just one
possible explanation. Aharonson said further study is needed to
determine whether the deposit could have been left there by the flow of
dust rather than water.

The latest research emerged when the Global Surveyor spotted gullies and
trenches that scientists believed were geologically young and carved by
fast-moving water coursing down cliffs and steep crater walls.

Scientists at the San Diego-based Malin Space Science Systems, who
operate a camera aboard the spacecraft, decided to retake photos of
thousands of gullies in search of evidence of recent water activity.

Two gullies that were originally photographed in 1999 and 2001 and
re-imaged in 2004 and 2005 showed changes consistent with water flowing
down the crater walls, according to the study.

In both cases, scientists found bright, light-colored deposits in the
gullies that weren't present in the original photos. They concluded the
deposits - possibly mud, salt or frost - were left there when water
recently cascaded through the channels.

The Global Surveyor, managed by NASA's Jet Propulsion Laboratory,
abruptly lost radio contact with Earth last month. Attempts to locate
the spacecraft, which has mapped Mars since 1996, have failed and
scientists fear it is unusable.

NASA's durable Mars rovers have sent scientists strong evidence that the
planet once had liquid water at or near the surface, based on
observations of alterations in ancient rocks.

"We're now realizing Mars is more active than we previously thought and
that the mid-latitude section seems to be where all the action is," said
Arizona State University scientist Phil Christensen, who was not part of
the current research.

Mars formed more than 4.5 billion years ago and scientists generally
believe it went through an early wet and warm era that ended after 1.5
billion to 2.5 billion years, leaving the planet extremely dry and cold.

Water can't remain a liquid for long because of subzero surface
temperatures and low atmospheric pressure that would turn water into ice
or gas.

But some studies have pointed to the possibility of liquid water flowing
briefly on the surface through a possible underground water source that
periodically shoots up like an aquifer.
Received on Wed 06 Dec 2006 12:11:15 PM PST