Mars Water is too SALTY to support Life

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.

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Phoenix Spacecraft lands on Mars

The U.S. space agency's Phoenix Mars lander sent a signal to Earth Sunday, indicating it reached the surface of the Red Planet, NASA said on its Web site.

Touchdown came shortly before 8 p.m. EDT, the space agency reported.

Phoenix, equipped with retro-rockets to slow its descent, plunged into Mars's atmosphere 78 miles above the surface at 12,750 mph, and then was traveling about 1.7 times the speed of sound when a parachute was deployed about 7.8 miles above the surface.

The Phoenix's heat shield, which had to withstand temperatures of about 2,600 degrees Fahrenheit during entry, was jettisoned about 15 seconds after the chute opened, NASA said.

Preparations were made to arrange for three Mars orbiting satellites to be in the right place on May 25, 2008, to observe Phoenix as it entered the atmosphere and to monitor it up to one minute after landing. This information will allow for better design for future landers.[15] The projected landing area was an ellipse 100 km by 20 km covering terrain which has been informally named "Green Valley"[16] and contains the largest concentration of water ice outside of the poles.

Phoenix entered the Martian atmosphere at nearly 13,000 miles per hour, and within 7 minutes had to be able to decrease its speed to 5 miles an hour before touching down on the surface. Confirmation of atmospheric entry was received at 4:46 pm PDT (23:46 UTC). Radio signals received at 4:53:44 p.m. PDT confirmed that Phoenix had survived its difficult descent and landed 15 minutes earlier, thus completing a 422 million mile flight from Earth. Radio signals, traveling at the speed of light, took a little over 15 minutes to reach Earth from Mars at the time of Phoenix's landing. The light travel time varies as Earth and Mars change their relative positions during their respective solar orbits. The landing was made on a flat surface, with the lander reporting only 0.25 degree of tilt. Just prior to landing, the craft performed a successful reorientation using its thrusters to allow the solar panels to deploy along an east-west axis to maximize power generation.

Only five of 13 previous attempted Mars landings were successful.

The first images from the Phoenix Lander:

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