Rather than hunt for microbes like the Viking missions of the 1970s, NASA's Mars Science Laboratory, nicknamed Curiosity, will look for places that could have hosted and preserved life.
"The term 'life-detection' is so ill-defined and so hard to ascertain it doesn't make a good starting point," said geologist John Grotzinger, with the California Institute of Technology.
Instead, NASA's new Mars mission, scheduled for landing on Aug. 6, is primarily a geological expedition to an intriguing piece of real estate called Gale Crater, located just south of the Martian equator.
Scientists believe the crater formed some 3.5 billion to 3.8 billion years ago when Mars, Earth and the rest of the planets in the inner solar system were regularly bombarded by meteorites.
Gale's most striking feature is not the 96-mile (154-km) wide pit in the ground, but a 3-mile-high a(5-km-high) mound of debris rising from the crater's floor. Scientists believe the mountain, located in the center of the basin, is the layered remains of sediment that once filled the crater.
Over time and by a process not well understood, the sediment was carried away, leaving what is now known as Mount Sharp, which scientists hope will reveal the geological history of Mars like no similar formation can do on Earth.