Phoenix set to land on Mars

May 13, 2008

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

Phoenix 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.

An artist's concept of NASA's Phoenix Mars Lander a moment before its 2008 touchdown on the arctic plains of Mars. Pulsed rocket engines control the spacecraft's speed during the final seconds of descent.

"This is not a trip to grandma's house. 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 of all attempts to land on Mars have succeeded."

Rocks large enough to spoil the landing or prevent opening of the solar panels present the greatest known risk. However, images from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter, detailed enough to show individual rocks smaller than the lander, have helped lessen that risk.

"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."

The landing site chosen for NASA's Mars Phoenix Lander, at about 68 degrees north latitude, is much farther north than the sites where previous spacecraft have landed on Mars.

Earlier in 2002, NASA's Mars Odyssey orbiter discovered that plentiful water ice lies just beneath the surface throughout much of high-latitude Mars. NASA chose the Phoenix proposal over 24 other proposals to become the first endeavor in the Mars Scout program of competitively selected missions.

"Phoenix will land farther north on Mars than any previous mission," said Phoenix Project Manager Barry Goldstein of NASA's Jet Propulsion Laboratory, Pasadena, Calif.

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

An artist's concept: Months after landing, Phoenix begins to shut down operations as winter sets in. Far-northern latitudes on Mars experience no sunlight during winter, depriving the solar-powered lander of electricity. Frost covering the region as the atmosphere cools will eventually bury Phoenix in ice.

"The Phoenix mission not only studies the northern permafrost region, but also takes the next step in Mars exploration by determining whether this frosty region, which may encompass as much as 25 percent of the Martian surface, is habitable," said Peter Smith, Phoenix principal investigator at the University of Arizona, Tucson.

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 itself.