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By University Communications
May 13, 2008

The Phoenix Mars Lander is preparing to end its long journey and begin a three-month mission to taste and sniff fistsfuls of Martian soil and buried ice. The lander is scheduled to touch down on the Red Planet May 25.

Phoenix, a mission led for NASA by The University of Arizona, will enter the top of the Martian atmosphere at almost 13,000 mph. In seven minutes, the spacecraft must complete a challenging sequence of events to slow to about 5 mph before its three legs reach the ground. Confirmation of the landing could come as early as 7:53 p.m. EDT.

"Putting a spacecraft safely on Mars is hard and risky," said Ed Weiler, associate administrator for NASA's Science Mission Directorate at NASA Headquarters in Washington. "Internationally, fewer than half the attempts have succeeded."

Rocks large enough to spoil the landing or prevent opening of the solar panels present the biggest known risk. However, images from the High Resolution Imaging Science Experiment, known as HiRISE, camera on NASA's Mars Reconnaissance Orbiter, detailed enough to show individual rocks smaller than the lander, have helped lessen that risk. The HiRISE team is based at UA, led by principal investigator Alfred McEwen of the Lunar and Planetary Laboratory.

"We have blanketed nearly the entire landing area with HiRISE images," said Ray Arvidson of Washington University in St. Louis, chairman of the Phoenix landing-site working group. "This is one of the least rocky areas on all of Mars and we are confident that rocks will not detrimentally impact the ability of Phoenix to land safely."

Phoenix uses much of the hardware from a spacecraft built for a 2001 launch that was canceled in response to the loss of a similar Mars spacecraft during landing in 1999.Phoenix principal investigator Peter Smith of UA's Lunar and Planetary Laboratory proposed the mission in 2002 because he saw the unused spacecraft as a resource for pursuing a new science opportunity.

Smith proposed the Phoenix mission after UA professor William V. Boynton's Gamma Ray Spectrometer on NASA's Mars Odyssey orbiter discovered earilier in 2002 that plentiful water ice lies just beneath the surface throughout much of high-latitude Mars.

NASA chose Smith's Phoenix proposal over 24 other proposals to become the first endeavor in the Mars Scout program of competitively selected missions. With that selection, UA became the first public university to lead a mission to Mars.

Phoenix will land farther north on Mars than any previous mission.

"The Phoenix Mission not only studies the northern permafrost region, but takes the next step in Mars exploration by determining whether this region, which may encompass as much as 25 percent of the Martian surface, is habitable," Smith said.

The solar-powered robotic lander will manipulate a 7.7-foot arm to scoop up samples of underground ice and soil lying above the ice. Onboard laboratory instruments will analyze the samples. Cameras and a Canadian-supplied weather station will supply other information about the site's environment.

One research goal is to assess whether conditions at the site ever have been favorable for microbial life. The composition and texture of soil above the ice could give clues to whether the ice ever melts in response to long-term climate cycles. Another important question is whether the scooped-up samples contain carbon-based chemicals that are potential building blocks and food for life.

The Phoenix Mission is led by Smith with project management at JPL. The development partnership is with Lockheed Martin, Denver. International contributions are from the Canadian Space Agency; the University of Neuchatel, Switzerland; the universities of Copenhagen and Aarhus, Denmark; the Max Planck Institute, Germany; and the Finnish Meteorological Institute.