May 20, 2008
After a nearly 10-month journey, the Phoenix lander will touch down on Mars May 25. Confirmation of the landing could come as early as 7:53 P.M.
EST. The descent and landing will be a nail-biter for mission controllers. The lander must slow from a speed of 13,000 miles per hour (20,900 kilometers per hour) to 5 miles per hour (8 kilometers per hour) in 7 minutes. The 904-pound (410 kilograms) craft will use rocket engines for the final 25 seconds of its descent after braking at higher altitude with parachutes. (View an animation of the landing here
.) In more recent missions, like the Spirit and Opportunity rovers in 2003, airbags provided cushioning for the final landing.
Launched August 4, 2007, Phoenix
is the first in NASA's Scout Program, which aims to conduct smaller, low-cost science missions. The craft's onboard laboratory will study the history of water and habitability potential in the martian arctic's ice-rich soils.
"Our landing area has the largest concentration of ice on Mars outside of the polar caps," said the mission's principal investigator, Peter Smith, of the University of Arizona, Tucson. "If you want to search for a habitable zone in the arctic permafrost, then this is the place to go."
Phoenix carries hardware from two unsuccessful missions: the Mars Polar Lander and the Mars Surveyor 2001 Lander. The Polar Lander crashed on Mars. Mars Surveyor was built but never launched.
Cold, arid Mars lacks standing water on its surface. But in the arctic regions, copious ice lies right below the surface. In 2002, the Mars Odyssey Orbiter located large amounts of subsurface water ice in the northern arctic plain.
Phoenix will visit this ice-rich area. Its robotic arm will dig through the protective topsoil layer to the water ice below. Then it will carry a sample of soil and ice to the lander's various onboard scientific instruments for study.
Phoenix's planned mission period is 92 Earth days. After that, the martian winter will settle over the craft. The waning light will deprive the solar-powered laboratory of electricity to run its instruments. Mission planners expect the lander to end its life covered in frozen carbon dioxide gas (dry ice). Chances are remote that Phoenix will hum back to life in spring.
The mission takes its name from the mythical phoenix bird that symbolizes rebirth. When the bird dies, it bursts into flames. A new bird then rises from the ashes of the pyre.