National Aeronautics and Space Administration scientists said the spacecraft has returned 73 terabits of data -- more than all earlier Mars missions combined.

The orbiter initially moved into position 186 miles above the surface of Mars in October 2006, subsequently conducting approximately 10,000 targeted observation sequences of high-priority areas. NASA scientists said the orbiter has imaged nearly 40 percent of the planet at a resolution that can reveal house-sized objects in detail, 1 percent in enough detail to see desk-sized features.

It also has covered nearly 60 percent of Mars in mineral mapping bands at stadium-size resolution, assembled nearly 700 daily global weather maps and dozens of atmospheric temperature profiles, along with radar profiles of the subsurface and the interior of the polar caps.

"These observations are now at the level of detail necessary to test hypotheses about when and where water has changed Mars and where future missions will be most productive as they search for habitable regions on Mars," said Richard Zurek, a project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

The orbiter now begins a new phase as Mars makes another orbit around the sun, which takes approximately two Earth years.