Mars Global – Surveyor (NASA)

(Text adapted from «NASA Science Mars Exploration Program«)

Launched November 7, 1996, Mars Global Surveyor became the first successful mission to the red planet in two decades. After a year and a half spent trimming its orbit from a looping ellipse to a circular track around the planet, the spacecraft began its prime mapping mission in March 1999. It has continued to observe the planet from a low-altitude, nearly polar orbit ever since.

The mission has studied the entire Martian surface, atmosphere, and interior. One of the most exciting observations of the spacecraft’s wide-angle camera system, known as the Mars Orbital Camera, is that the red planet has very repeatable weather patterns. Each day the camera operates, it collects images that are used to build up a daily global map. These maps provide a record of changing meteorological conditions on Mars. Weather patterns observed by the spacecraft include some dust storms that repeat in the same location within a week or two of the time they occurred in the previous year. 

A panoply of high-resolution images from the Mars Global Surveyor has documented gullies and debris flows suggesting that occasional sources of liquid water, similar to an aquifer, were once present at or near the surface of the planet.

By studying Mars for several Martian years (a Mars year is about twice as long as an Earth year), Mars Global Surveyor has has observed gully formation, new boulder tracks, recently formed impact craters, and diminishing amounts of carbon dioxide ice within the south polar cap. Findings such as these have shown that Mars is a dynamic planet with a history of seasonal and long-term change recorded in the planet’s surface.