The Mars 2003 orbiter would be similar to the veteran Mars Global Surveyor launched in 1996, which is seen here. Photo: NASA/JPL

NASA's Mars Global Surveyor spacecraft, which has collected more information about the red planet than all previous missions combined, completed its primary science mission yesterday and now begins a new era of continued exploration.

"By any conceivable measure the scientific impact of Mars Global Surveyor has been extraordinary. In many ways we now know Mars to be a different planet than when the spacecraft arrived in 1997, and our perspective continues to evolve as the data keep flowing," said Dr. Arden Albee, Global Surveyor project scientist at the California Institute of Technology in Pasadena. "In some aspects, we now have better maps of Mars than we do of Earth."

During the primary science mission, the spacecraft studied the climate, surface topography and subsurface resources and mapped the entire planet," said Tom Thorpe, Global Surveyor project manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "The extended mission will continue to take advantage of these extraordinary mapping capabilities and the data will be used to select future landing sites for several upcoming missions."

Mars Global Surveyor's extended mission has been approved through April 2002.

The robotic orbiter was launched on Nov. 7, 1996, and arrived at Mars on Sept. 12, 1997. The spacecraft began its primary mapping mission in March 1999 and has collected data for a full Martian year, equivalent to about two Earth years. Those comprehensive observations are proving invaluable to understanding the seasonal changes on Mars.

Some of the most significant findings of the mission include:

• Enticing evidence for recent liquid water at the Martian surface.
  
  
• Dramatic evidence for layering of rocks that points to widespread ponding of water or lakes on Mars in its early history.
  
  
• The first good estimate of the amount of water currently trapped in both Martian polar caps combined -- about one and a half times the amount of ice in Greenland.
  
  
• Topographic evidence for a South Pole-to-North Pole slope that controlled the transport of water and sediments, and recognition of the flat Northern Hemisphere that has been proposed as the possible site of an ancient ocean.
  
  
• The surprising detection of highly magnetized crust in the Southern Hemisphere, which indicates rapid cooling of Mars in the beginning of its history that may have contributed to its earlier, warmer climate.
  
  
• The first reliable models of the crustal structure of Mars, including the detection of ancient impact basins and possible channels buried beneath the northern plains.
  
  
• Identification of the mineral hematite, indicating a past surface-hydrothermal environment that may be an analog for the kinds of areas in which early life developed on Earth.
  
  
• Significantly improved understanding of the dynamics of the atmosphere, including the monitoring of cyclonic storms, and the daily and seasonal behavior of carbon dioxide and water ice clouds.
  
  
• Extensive evidence for the role of dust in re-shaping the recent Martian environment in the form of dust devils, dust storms, dunes and sand sheets.

As of 4:33 p.m. PST (7:33 p.m. EST) January 31, 2001, the spacecraft had made 8,505 orbits of the planet and taken more than 58,000 images, 490 million laser-altimeter shots to measure topography and 97 million spectral measurements.

The Global Surveyor mission is managed by JPL for NASA's Office of Space Science, Washington, D.C. Lockheed Martin Astronautics, Denver, Colo., developed and operates the spacecraft. JPL is a division of the California Institute of Technology.