May 29, 2008 -- The debate about whether Mars once had water is pretty much over. The new quandary is if the water was suitable to support life.
As one group of scientists prepares for the first sampling of Mars' water with the Phoenix space probe, which landed on the Red Planet last Sunday, another team of researchers has nixed life's prospects there after studying salt deposits left behind on the planet's surface.
"If Martian life had to contend with the conditions we found, it certainly would have had a tough time," said Nicholas Tosca, a Harvard University geochemist and lead author of a paper on the research appearing in this week's Science.
Using data collected by the Mars rover Opportunity and other probes, Tosca and his colleagues determined that the planet's water would have been too salty for all but a handful of Earth's organisms to survive.
"If there is a window of life to survive on Mars, it's probably pushed back to when the planet was very young," Tosca told Discovery News.
As tough as survival would have been at Meridiani Planum, where Opportunity found evidence of an ancient shallow ocean, it would have been worse elsewhere, Tosca added.
Mars lost most of its atmosphere over time, leaving an extremely arid and cold desert similar to Antarctica.
"That's not to say that no life can occur under those conditions," Tosca said. "But there were times when it was friendlier."
Life on Earth is believed to have begun about 3.5 billion years ago. The planet's salt-loving micro-organisms actually evolved from ancestors that didn't do so well in briny water, said Tosca, who works with a team at Harvard studying the origin of life on Earth.
"The starting point for life on Earth was easier than on Mars," Tosca said.
Because liquid water is required by all living organisms on Earth, its presence is believed to be a prerequisite for life elsewhere.
"Further evaluation of habitability, however, requires that we move beyond the mere presence of water to consider its properties," the researchers wrote.
Not all waters are habitable, they added. The limits of terrestrial life are defined by additional parameters, including temperature, pH and salinity.
"From what we know about the origins of life on Earth, an acid pH and high salinity might not have worked so well for the evolution of life on Mars," Tosca said.
Related Links:
Irene Klotz's blog: Free Space
How Stuff Works: Mars Phoenix Lander
our sites
video
mobile
shop
stay connected
corporate
