Ice-sampling probe set for Sunday landing on Mars

By Irene Klotz

PASADENA, California (Reuters) - A new chapter in Mars exploration opens on Sunday when a small robotic probe jets down to the planet's arctic circle to learn if ice beneath its surface ever had the right chemistry to support life, mission managers said on Thursday.

NASA approved the mission, known as Phoenix, after the Mars orbiter Odyssey found ice surrounding the polar caps in 2002. Five probes landed near Mars' equatorial zones, including the rovers Spirit and Opportunity, which discovered signs of past surface water. Odyssey found no sign of buried ice around Mars' equator.

"We're going way to the north," said Peter Smith, a planetary geologist at the University of Arizona in Tucson who heads the Phoenix science team.

On Earth, the arctic regions hold the history of the planet's climate changes, which are locked layer by layer into the ice core.

"This is where the history of life is preserved in its purest form -- organic molecules and cellular bacterial microbes and so forth," Smith said.

"We're wondering if this is true on Mars," he said.

Phoenix is not going to search for life directly, but it should be able to determine if the Martian ice was ever liquid. Liquid water is believed to be an essential ingredient for life to exist.

Among Phoenix's science instruments are small ovens to vaporize and chemically analyze the Martian ice, revealing, some of the processes the molecules underwent before reaching their present condition. Other sensors will study minerals in the soil and ice and image the shape and structure of individual grains in the soil.