Mars Odyssey, which arrived Tuesday at the red planet, will beam geological data.
Written in the rust-red dust, sand, and rock of Mars is the history of water - a compound vital to organic life.
A key tool for unlocking that history has started to trace ever-tighter orbits around the red planet. NASA's 2001 Mars Odyssey orbiter, a solar-powered digital geologist launched last April, is preparing to take up a 2-1/2-year search for clues to the story of water - and, perhaps, of life - on Mars.
In the process, the craft, which arrived at Mars late Tuesday, is breathing new life into US efforts to explore a planet that has captivated the human imagination for millenniums. Mars Odyssey's successful 285-million-mile journey stands in stark contrast to a pair of high-profile Mars missions in 1999 that reached the planet only to be destroyed.
"How sweet it is!" said Daniel Goldin, outgoing administrator of the National Aeronautics and Space Administration, shortly after Mars Odyssey signaled its safe arrival.
His feeling was widely shared. When the orbiter's motor fired to put it into orbit, it hurtled around the backside of Mars, entering a period of radio silence that mission manager David Spencer called "the longest 20 minutes of my life." When Mars Odyssey emerged, cheers and applause erupted in the control center.
Although the craft is now orbiting Mars, it won't begin in earnest the science part of the $297 million mission until February. It will take nearly that long for flight controllers to adjust the orbit's shape so the craft can fulfill its objectives of mapping the chemical composition of the surface and "sniffing" for possible deposits of water ice just below the surface in some regions.
The chemical makeup of rocks and minerals is expected to yield clues about the planet's past climate and how that influenced on Mars' water resources.
Researchers divide roughly into two camps on these topics. One holds that early in its history, the planet was warmer, wetter, and had an atmosphere thick enough to support the presence of vast amounts of surface water. The other camp posits that the planet has always been cold, and that any water would have been locked up as subsurface ice. Periodically, however, that ice could melt and gush to the surface.