Phoenix Mars Lander: Hunt for Red Planet ice

By Jeremy Hsu

updated 1:36 p.m. ET May 21, 2008

The Phoenix Mars Lander set to land Sunday may represent a clean slate for NASA's past failed or canceled Martian missions, but its technological lineage also resembles Frankenstein's monster.

The spacecraft will land on the Red Planet with baggage that includes a backhoe-like robotic arm, a miniature chemistry set, and a laser-guided weather station.

"Most of the instruments have heritage from other missions," said Michael Gross, Phoenix payload manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

Those heritage technologies developed for previous Mars missions such as Mars Surveyor Lander and Mars Polar Lander came in useful to outfit the $420 million Phoenix mission, which seeks to uncover the history of water on Mars by digging beneath the arctic surface. The spacecraft is set to land on May 25 on a six-month mission to determine whether the region may have once been habitable for primitive life.

Digging the Red Planet
However, Gross and other engineers had to remind themselves that Phoenix's new science mission came with new demands.

"We were counting on the heritage of the 2001 (Mars Surveyor Lander) arm, and we had to redesign the whole thing," Gross told SPACE.com. "There's a comfort level, but also pitfalls with heritage that you want to make sure you don't walk into."

The original robotic arm lacked the physical power to dig into the frozen Martian tundra, so engineers strengthened the joints and switched the arm material from aluminum to steel. They also replaced the original scoop with the Icy Soil Acquisition Device, which has several tricks to deal with the ice-hardened layer beneath the looser regolith soil on the surface.

First the nearly eight-foot robotic arm uses a backhoe motion to clear away loose regolith and expose the icy layer. A blade on the front of the scoop can try a bit of scraping, but the real digging for ice samples requires a small drill in the back of the scoop.

The spring-loaded drill is sprung against the ground and turned on, rotating and grinding against the icy soil using the spring's pressure. Wrist movements push the loosened ice samples into a chamber for further testing.

"Within about a minute or so, it kicks a fair amount of material into the scoop or chamber," said Peter Smith, Phoenix principal investigator at the University of Arizona, Tucson. Smith added that the drill would do its excavation two or three times.

The robotic arm also has scraper blades on the bottom that can clear away material and continue tearing up the icy regolith, Gross said. The arm can dig down as far as 20 inches, the deepest that anyone has gone on Mars.

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