Aiming for Mars: NASA's Phoenix Lander Prepares to Fly

A NASA spacecraft wielding a trench-digging robotic arm is poised for a Saturday launch towards the north pole of Mars to find out whether the icy region sports an environment suitable for microbial life.

The three-legged Phoenix Mars Lander is set to launch at 5:26:34 a.m. EDT (0926:34 GMT) atop a Delta 2 rocket from the Cape Canaveral Air Force Station in Cape Canaveral, Florida. It?s destination: the arctic martian plains of Vastitas Borealis.

?Is this a habitable zone? This is really a major question for us,? said Peter Smith, the Phoenix mission?s principal investigator at the University of Arizona, during a Thursday briefing. ?One that we hope to answer.?

Icy quarry

Observations from spacecraft orbiting Mars have shown Phoenix's planned landing site to be rich in subsurface ice, a tantalizing target for researchers tracking the history and role of water on the red planet. Phoenix is designed to use its robotic arm-mounted scoop to dig into and collect samples of Mars? surface, then scan them with a host of onboard instruments.

But reaching Mars has historically been tough, particularly since the planet is rather unforgiving to small errors. More than half of all the missions sent to Mars have ended in failure.

NASA?s ill-fated Mars Polar Lander, for example, suffered an apparent early shutdown of its descent rocket engines in 1999, likely sending the craft plummeting to its destruction on the martian surface. Phoenix carries many of the same instruments as its polar-bound predecessor in an effort to recoup some of that lost science.

?It?s challenging, no doubt. Anytime you try to land on Mars, it?s a challenge,? said Doug McCuistion, director of NASA?s Mars Exploration program. ?But the payoff is worth the risk.?

The $420 million Phoenix mission is expected to land on Mars on May 25, 2008 for an initial 90-Martian day expedition. NASA?s Jet Propulsion Laboratory (JPL) in Pasadena, California will manage the expedition.

If successful, Phoenix?s Mars landing next year will be the first soft touchdown since NASA?s Viking missions in the 1970s, mission managers said.

Sampling Mars

Built by Lockheed Martin, the 772-pound (350-kilogram) Phoenix lander is NASA?s first Mars Scout Program mission to explore the red planet with small, relatively low-cost robots.

?We?re there to study the air, the dirt and the ice in this northern polar region,? said Leslie Tamppari, NASA?s Phoenix project scientist at JPL, of the probe?s mission.

Much of the spacecraft and its seven instrument suites draw on equipment built for NASA?s canceled Mars Surveyor 2001 Lander and the lost Mars Polar Lander.

?Phoenix had an inherent advantage in that it had a lot of inherited hardware,? said Ed Sedivy, Phoenix Spacecraft Program for Lockheed Martin, adding that the probe has undergone a barrage of tests to ensure it will work properly. ?It really gave us a leg up in driving the risk down.?

Folded away aboard Phoenix is its eight-foot (2.4-meter) robotic arm, which carries a camera and instruments to study martian soil, as well as a spiked scoop strong enough to bite into ice as hard as concrete.

Lining the probe?s top, or deck, are more cameras, a wet chemistry laboratory, eight miniature ovens and other tools to determine the chemical makeup of Mars? ice and soil with a special focus on the presence of organic compounds. Such complex compounds and liquid water are thought to be among the requirements needed to support primitive life, Phoenix researchers said.

Each tiny oven can only be used once and will cook just a pinch of martian soil -- about 30 microliters -- and then analyze the leftovers.

?When the oven is heated?it gives off vapor just like cookie dough in your kitchen,? said the oven instrument?s lead scientist William Boyton, of the University of Arizona. ?And we use that to see what?s going on.?

Red planet weather station

Phoenix is also equipped to serve as the first polar weather station on Mars.

The lander?s four-foot (1.2-meter) meteorology mast gives the probe a total height of just over seven feet (2.2 meters) and carries a series of heat sensors to measure atmospheric temperature at different heights. A small cylinder tethered to the top of the mast will indicate wind direction, Phoenix researchers said.

A laser detection and ranging (lidar) tool will beam light into the martian sky, then measure the amount reflected back to track atmospheric particles and clouds.

?I?m excited about finding Earth-like clouds at Mars,? Deborah Bass, NASA?s deputy Phoenix project scientist at JPL, told reporters Wednesday.

While Mars researchers are targeting a 90-Martian day mission for Phoenix, they don't expect the lander to last as long as NASA's hardy rovers Spirit and Opportunity, which are currently hunkered down to weather a massive dust storm in their fourth year of an initial three-month mission.

?Once winter approaches, we will be immersed in solid carbon dioxide ice,? Smith said. ?It will certainly not survive that kind of winter.?

NASA will broadcast the Phoenix Mars Lander?s launch live on NASA TV beginning at about 3:30 a.m. EDT (0730 GMT).

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