A Phoenix on Mars

Searching for habitability on the Red Planet

A new emissary from Earth is set to parachute onto Mars May 25, making it the first craft to land on the Red Planet’s north polar region.

CAN MARS SUPPORT LIFE? Artist’s depiction of Mars Phoenix Lander on the planet’s icy northern polar region JPL/NASA, UA

NASA’s $386-million Phoenix Mars Lander features a robotic arm — similar to a backhoe — that will dig trenches up to half a meter deep in the frigid soil, scraping and scooping up samples of ice that previous satellite studies indicate lie just a few centimeters beneath the surface. Phoenix will deliver those samples to onboard detectors — eight miniature ovens, four laboratory wet cells and a mass spectrometer — to determine if the region contains water, complex organic compounds and sources of energy that might support life.

Phoenix got its moniker because it inherited instruments from the Mars Surveyor Lander, canceled in 2000, as well as detectors similar to those on the Mars Polar Lander, lost in 1999. Scheduled to land at 68° N, the latitude of northern Alaska, Phoenix will function for three months but might last twice as long, until the shorter, colder days of winter hamper the solar-powered craft.

In searching for a current habitat on the Red Planet, Phoenix revives an endeavor attempted with the 1976 Viking missions. However, Phoenix’s ovens slowly heat ice samples up to 1,000° Celsius, whereas Viking flash-heated material to 500° C. The expanded temperature range is critical for identifying various organic compounds and monitoring the transition from solid to liquid to gas, notes Phoenix’s principal investigator, Peter Smith of the University of Arizona in Tucson.

Those materials that vaporize at temperatures from about 300° C to 600° C “could be the complex organic compounds we’re looking for,” Smith says. Vaporization at higher temperatures may signify organic compounds delivered to the Martian surface by asteroids or comets.

Compared to the Viking missions, which assumed that Mars harbored life, “we are just looking for a habitable zone,” says Smith. “We don’t measure DNA. We don’t measure proteins.”

“The likelihood that life is present in the near surface is next to nil due to the nasty radiation environment,” comments John Mustard of BrownUniversity in Providence, R.I. “It’s best to build first towards habitability — when, where and how — and then move toward life detection on the basis of those results.” Phoenix “is not sexy in that it does not look for microbes, but it’s very important.”

Like a pair of eyes, twin cameras atop the craft’s 2-meter-long mast will provide a 3-D infrared and visible-light panorama of the arctic terrain that shows features as small as a few millimeters across. Optical and atomic-force microscopes will take close-ups of soil and water-ice samples, recording features as small as one-hundredth the width of a human hair — the tiniest details ever taken on the Red Planet.

Shooting lasers into the Martian atmosphere, Phoenix will examine its density and composition up to 20 kilometers in altitude. The data will provide information about the formation, duration and movement of clouds, fog and dust plumes.

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