Last week, flight controllers at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., breathed a collective sigh of relief. Although in 1999 they had lost the last two spacecraft that journeyed to Mars, their current mission to the Red Planet had completed a risky maneuver, using the friction of the Martian atmosphere to begin settling into its designated orbit 400 kilometers above the surface. Early next month, if all continues according to plan, the Mars Odyssey craft will begin a 2-year exploration of the composition of the Martian surface, hunt for near-surface deposits of water, and examine the planet’s radiation background. Odyssey embarks on its mission at a time when questions about past and present conditions on the planet, including its water content and ability to harbor life, seem more puzzling than ever. “We’re in state of maximal confusion,” says planetary geologist David A. Paige of the University of California, Los Angeles.