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.
Get more information on the Phoenix Mars Mission:
University of Arizona's Phoenix Mars Mission site.
The Planetary Society: We're Launching to Mars!
NASA: Missions to Mars.
