NASA selected today a new lander mission to explore the high northern latitudes of Mars. That zone is thought be the site of a rich reservoir of sub-surface ice.

Under the space agency's Mars Scout program, the University of Arizona's Lunar and Planetary Laboratory will build Phoenix. The craft is set to haul a set of built but never flown instruments designed for a cancelled 2001 Mars Surveyor Lander.

To be launched in 2007, Phoenix would come to rest on terrain suspected of harboring as much as 80 percent water ice by volume within one foot of the surface. The lander would carry out the first subsurface analysis of ice-bearing materials on another planet.

The now orbiting Mars Odyssey spacecraft has charted what appears likely to be huge reservoirs of ice under the red planet's topside.

Peter Smith of the University of Arizona, Tucson, is the team leader for Phoenix. Once landed, the probe would be able to make a very accurate analysis of what promises to be some of Mars' more habitable terrain, he said, a place where organics may have a stable environment.

Phoenix would carry improved, but never flown, 2001 Mars Surveyor Lander instruments, in addition to Smith's stereo imaging camera and robotic arm.

The Phoenix lander includes an instrument suite designed to completely characterize the accessible ice, soil, rock, and local atmosphere using state-of-the-art methods.

Included within the instrument payload are microscopic imaging systems capable of examining materials at scales down to 10 nanometers (i.e., 1000 times less than the width of a human hair), while others will investigate whether organic molecules are contained in ice or soil samples.

Also onboard is a thermal and evolved gas analyzer (TEGA) that was carried on the ill-fated Mars Polar Lander that apparently plowed into the red planet in December 1999.

TEGA is the product of University of Arizona planetary scientist William Boynton, co-investigator on the Phoenix mission. Both Smith and Boynton had science instruments on the lost Mars Polar Lander.

The mission of Phoenix is focused on two goals. One is to study the geologic history of water on Mars, the key to unlocking the story of past climate change. A second objective is to search for evidence of a habitable zone that may exist in the ice-soil boundary, a find that might mean hitting "biological paydirt."

Smith leads the Phoenix mission in a partnership with NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, and Lockheed Martin Space Systems in Denver, Colorado.

In addition, the Canadian Space Agency is contributing a meteorological package that includes a Light Detection And Ranging (LIDAR) sensor to study polar climate.

NASA's Ed Weiler, Associate Administrator for Space Science at NASA Headquarters in Washington, D.C. selected Phoenix over three other concepts: a Mars airplane, an orbiter, and a novel sample return of martian atmospheric dust.

The tough competition between the four novel Mars Scout missions has been underway over the past year.

The Mars Scout program is designed to complement major missions being planned as part of NASA's Mars Exploration Program, as well as those under development by foreign space agencies.

A Scout mission comes with a total mission cost cap of $325 million.

The Mars Scout Program is managed by JPL for NASA's Office of Space Science in Washington, D.C.