Probe Aiming to Land on Mars Ice

Aug. 3, 2007 — For the past decade, NASA's plan for exploring Mars has been to follow the trail of water. On Saturday, the agency plans to launch a robotic probe that will land right on it.

The spacecraft, called Phoenix, will be the first to explore the frozen polar region of Mars, an area that is believed to hold vast reservoirs of water ice.

"Water and life go together," said Ray Arvidson, with Washington University in St. Louis and one of the lead scientists on the Phoenix mission. "We want to confirm that water ice is just below the surface."

Scientists have many questions about Mars' water. Previous spacecraft, including the twin rovers Spirit and Opportunity, turned up ample geologic and chemical signs that water once existed on what is now a cold and dry desert. But no one knows what happened to it, nor if it was in a liquid state long enough for life to evolve.

Phoenix will not directly look for life on Mars. Instead the probe will use a 7.7-foot-long robotic arm to drill down into the frozen ground and retrieve ice samples to determine if Mars was chemically suited to support life.

"The greatest result we can find is that there is a wealth of complex organics associated with that ice. That would give us the sense this is the place to go search for life on Mars," said Phoenix lead investigator Peter Smith, with the University of Arizona.

Unlike NASA's intrepid rovers, which are still waiting out dust storms before they can continue with their investigations, Phoenix will remain stationary at its landing site. The journey to Mars, which is scheduled to begin with launch aboard an unmanned Delta rocket at 5:26 a.m. ET on Saturday, will take nine months.

Engineers have taken great pains to avoid the fate of some of Phoenix's predecessors, including Mars Polar Lander, which carried some of the same instruments now aboard the new probe.

Polar Lander was the second of two Mars probes lost in late 1999 as they attempted to settle on or around the planet. NASA canceled a lander mission that was to have been part of the 2001 Mars Surveyor mission in the wake of the accidents.

As its name implies, Phoenix, a mythical bird that reforms from its ashes, is a resurrection of that craft as well.

"We have tested and tested again to make sure we pulled out all the risk we could," spacecraft program manager Ed Sedivy, with manufacturer Lockheed Martin Space Systems, said a a news conference on Thursday.

The lander has several instruments to analyze soil and ice samples, including eight tiny ovens to heat pinches of soil to about 1,800 degrees Fahrenheit. Gas analyzers will then sniff the vapors to determine what chemicals are present.

"If we do find organic molecules, we won't be able to say that they definitely came form life in the past, said University of Arizona researcher William Boynton, a lead investigator for one of Phoenix's seven science instruments.

Organic material may have been delivered to Mars by meteorites, for example.

"We really aren't going there to identify life or look for past life," Boynton added. "We're going there to really understand whether conditions were right for life."

Phoenix also sports an advanced digital imaging system and a meteorological station built by the Canadian Space Agency.

NASA has until Aug. 24 to get Phoenix off the ground or face a 26-month delay until Earth and Mars are again favorably aligned for the spacecraft's 430-million-mile journey. Touchdown in the artic Martian plains of Vastitas Borealis is scheduled for May 25, 2008.

NASA will attempt its first soft-landing on Mars since the Viking missions of the mid-1970s. Instead of airbags, like the twin rovers and their predecessor Mars Pathfinder used to cushion their landing, Phoenix will use thruster rockets for the final moments of descent and land on three legs.

The probe will be landing as summer begins on Mars' northern hemisphere, giving scientists about three months for their studies before the probe freezes over.

So far, Phoenix's biggest obstacles have been too much water on Earth.

Summertime rain showers in Florida have hampered efforts to prepare Phoenix's launcher for flight, but forecasters on Friday predicted clear skies for Saturday's launch.

Any delays however, could impact NASA's plans to launch the space shuttle Endeavour and seven astronauts on a construction mission to the International Space Station. Both vehicles need tracking and safety services from the Eastern Test Range, which requires two days to reconfigure equipment for the different vehicles.

The shuttle's launch is targeted for 7:02 p.m. ET on Tuesday.

University of Arizona's Phoenix Mars Mission site.

The Planetary Society: We're Launching to Mars!

NASA: Missions to Mars.