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Mars Global Surveyor

Mars Global Surveyor mission graphic

Phase: Past

Launch Date: November 07, 1996

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Program(s):Mars Exploration

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Mars Global Surveyor was the first successful U.S. mission launched to Mars since the Viking mission in 1976. After a 20-year absence at the planet, Mars Global Surveyor ushered in a new era of Mars exploration with its pioneering science investigations. Mars Global Surveyor arrived at Mars on September 11, 1997, and has contributed a multitude of findings, including signs of past, persistent water such as an ancient delta and currently active water features in the gullies of canyon walls. After nearly a decade of discovery, MGS went silent in November, 2006.

Winter on Mars

Scientists have known for years that the polar caps on Mars shrink and grow between the Martian summer and winter seasons. But they wondered just how much carbon dioxide 'snow' is deposited each season? Are the frost deposits more like snow or more like ice? What role do the ice caps play in seasonal changes on Mars? Now new research from MOLA, the laser altimeter aboard the Mars Global Surveyor, may provide answers to these questions.

The image on the top is colored with a mosaic from the MOC camera. The image on the bottom is colored according to the relative height of the surface features. Elevation measurements taken by MOLA in combination with gravity determined by tracking the MGS spacecraft have been used to measure seasonal changes in the thickness of seasonal frost deposits and to provide the first direct measurement of their density.

The spacecraft's longevity is a testament to innovative engineering, and it has enabled scientists to develop an unprecedented understanding of how the martian landscape and seasons have been changing over time. When Mars Global Surveyor launched on November 7, 1996, it carried with it a limited amount of propellant, and the spacecraft was expected to run out of fuel in April of 2003, ending the capability to steer the ship with small engine thrusters and point the science instruments accurately. In August of 2001, the Mars Global Surveyor team implemented a clever "angular momentum management" strategy that minimized the need for thrusters to help stabilize and balance the spacecraft and kept it on target over viewing areas on the surface of Mars. Part of the angular momentum management scheme tipped the spacecraft at an angle 16 degrees backwards (instead of pointing straight down at the surface), which effectively cut the use of fuel by 800%.

Mars Global Surveyor was designed to circle in a polar orbit (traveling over the north pole to the south pole and back to the north pole) once every two hours, twelve times a day, collecting global "snapshots" from 400 kilometers (249 miles) above the martian surface. While the spacecraft is no longer operating, the scientific data it returned will continue to be studied for decades to come. During the mission, scientists gleaned valuable new information on daily and seasonal weather patterns, geological features and the migration of water vapor from hemisphere to hemisphere over time. The spacecraft's laser altimeter gave scientists their first 3-D views of the striking topography of Mars. Mars Global Surveyor's suite of science instruments included a high-resolution camera and a mineral detector that have helped engineers and scientists select safe landing sites rich in various minerals like hematite, a mineral often formed in liquid water, that help rover and landed missions search for more clues about the history of water on Mars.

In a landmark discovery, imaging scientists have seen gullies and debris flow features that suggest there could be current sources of liquid water at or near the surface of Mars. While all current Mars missions aim to understand the role of water on Mars to unlock the mystery of whether life could have developed on Mars in the past or may survive in the subsurface now or in the future, Mars Global Surveyor also has been able to characterize the topography, gravity, magnetic fields, thermal properties, surface composition, and atmosphere of Mars.