SPACE.com -- Mars Global Surveyor Mission Reveals Precarious Terrain

Late in June 2001, southern winter transitioned to spring and a wind began to blow. A comparitively small gust of dusty atmosphere was spotted by MGS (left). By the end of July the entire planet, except for the south polar cap, was covered by the dusty shroud (right). Planetary wind storms like these are common on parched Mars. Click to enlarge.

The second mission of MGS has provided several oppurtunities to create 3-D images by combining images of two slightly different angles. Two images were taken in October 2000 and May 2001 of these large formations in the Northern Terra MeridianiHere, four buttes and a pinnacle composed of eroded, layered rock are shown. The buttes formed as harder top layers sheilded lower layers from weathering. The area is 1.8 miles across. Click to enlarge.

The MGS captured this image on March 29, 2001 of a tributary valley in the enormous Nirgal Vallis. The patterns of the dunes reveal their shape and orientation control wind patterns. Small meteor craters in the dunes left of center indicate the dunes are much older than observers first thought. Click to enlarge.

MGS finally got a chance to capture images of the north polar cap after two years of sub-optimal conditions. This image reveals that sandy layers underneath harder, darker material, is weathering away. The result is a scale-like surface, where the darker, harder material, is supported by sand not yet blown away. The sand is blowing into dunes on the left side of the image, which is 1.9 miles wide. Click to enlarge.

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	Mars Global Surveyor Mission Reveals Precarious Terrain By SPACE.com Staff posted: 08:20 am ET 09 May 2002

Now in its extended mission, the Mars Global Surveyor is revealing intriguing features of our neighboring planet once veiled by enormous dust storms

Now in its extended mission, the Mars Global Surveyor is revealing intriguing features of our neighbor as a planet once veiled by enormous dust storms.

The latest images also reveal that Mars' northern pole may hold only half as much water in its ice cap than previously thought, along with unusual geologic features that tell of their age and the planet's wind patterns.

The Surveyor or MGS as it is called continues to add to its photo archive of over 93,000 images of the Red Planet.

Surveyor's prolific progress was delayed last June when seasonal winds began kicking up unusually large dust clouds. Except for the South Pole, the storm eventually veiled most of the planet for five months.

The MGS mission had to wait a long time for a good look at the North Pole, an area on Mars of great interest because it holds water ice. In 1999, a local dust storm made the atmosphere too hazy to see through. Then long winter nights obscured the area in 2000, followed by a springtime frost that heavily coated the ground.

All these confounding factors finally subsided in early 2001, and MGS's Mars Orbiter Camera spied the North Pole successfully. The pictures reveal that less ice is there than thought, as well as showing the erosion processes of its dunes.

Apparently, lower layers of sand are being slowly blown from underneath the harder upper layers. These are now seen to be precariously perched atop progressively thinner scarps.

MGS found evidence of similar balancing acts in the Northern Terra Meridiani. This area is near the intersection of the Martian equator and prime meridian, and comparable in size and character to Monument Valley in Utah and Arizona.

MGS gazed upon the Meridiani in its primary mission, but the newer images were taken from a slightly different angle. Combining the different angles in one image now gives a stereoscopic or "3-D" impression of the formations. Images like these will allow for better understanding of Martian geology in the future.

Finally, an new image captured of Nirgal Vallis, a 260-mile-long (420-km) valley further South of the Meridiani, reveals the valley floor of is composed of smaller, tributary valleys that have dunes and ripples of unique orientations from each other. MGS scientists believe the orientations of these features control the winds blowing above them.

Some of these dunes also appear to have ancient meteor craters within them, indicating the Nirgal Vallis dunes are older than previously thought.

Mars Global Surveyor has performed longer than previously thought. Yet the spacecraft continues to make valuable observations of our neighboring planet.