Mars Global Surveyor
Mars Orbiter Camera

Mars Orbiter Camera (MOC) High Resolution Images:

Exhumed Crater in Kasei Valles


Mars Global Surveyor Mars Orbiter Camera Release:          MOC2-68a, -68b, -68c
Mars Global Surveyor Mars Orbiter Camera Image ID:         581474713.34504
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(A) Regional context of the Viking 1 Orbiter and Mars Global Surveyor images shown below in (B) and (C), respectively. The Viking 1 image is represented by the large white box, the Mars Global Surveyor image is represented by the small white box. The area shown here includes the a portion of the Kasei Vallis outflow channel system. The large crater in the upper center of this context scene is 95 kilometers (59 miles) in diameter and is named Sharonov (after Russian astronomer, V.V. Sharonov (1901-1964)). The small white box is centered at 24.3°N, 61.5°W. This is a mosaic of Viking Orbiter images compiled by the U.S. Geological Survey. North is up.

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(B) Local context for Mars Global Surveyor MOC image 34504. The location of the MOC image is shown as a white box. A bar 10 km (6.2 miles) wide is shown for scale. The "N" arrow indicates the direction of North. This is a subframe of Viking 1 Orbiter image 226a08, taken in 1977. Illumination is from the left.

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(C) Mars Global Surveyor Mars Orbiter Camera image 34504 subframe centered at 24.3°N, 61.5°W on a crater at the base of a mesa in the Kasei Valles system. The large (approx. 670 Kbyte) image has been reduced approximately 3X relative to the raw image. The scale bar represents 2 km (1.2 mile). Illumination is from the right.

You may need to adjust the images for the gamma of your monitor to insure proper viewing.

Note: This MOC image is made available in order to share with the public the excitement of new discoveries being made via the Mars Global Surveyor spacecraft. The image may be reproduced only if the image is credited to "Malin Space Science Systems/NASA". Release of this image does not constitute a release of scientific data. The image and its caption should not be referenced in the scientific literature. Full data releases to the scientific community are scheduled by the Mars Global Surveyor Project and NASA Planetary Data System. Typically, data will be released after a 6 month calibration and validation period.

Click Here for more information on MGS data release and archiving plans.


Mars Global Surveyor's high resolution Mars Orbiter Camera (MOC) is providing scientists with a whole new way of looking at Mars. Able to see objects down to the size of automobiles and houses, results from the first year of MOC operations are suggesting that the red planet has had a complicated history that was very different from that of the only two places that geologists have visited in person: the Earth and the Moon.

An example of the complexity of martian geologic history is shown by a crater in Kasei Vallis that was imaged during the 345th orbit of Mars Global Surveyor at 5:44 p.m. PDT on June 4, 1998. MOC image 34504 (see (C), above) shows a 6 kilometer- (4 mile)- diameter crater that was once buried by about 3 kilometers (2 miles) of martian "bedrock."

Kasei Vallis is actually a system of giant channels thought to have been carved by catastrophic floods that occurred more than a billion years ago. A similar scenario was proposed to explain the Ares Vallis channel, where Mars Pathfinder landed in July 1997.

The Kasei Valles floods carved a deep and wide system of channels into the northern portion of Lunae Planum--a vast, relatively flat plain made up of layered rock that formed some time before the floods.

The crater shown above was partly excavated by the Kasei Valles floods. The crater is poking out from beneath an "island" in the Kasei Valles. The mesa was created in part by the flood, and by subsequent retreat--by small landslides--of the scarp that encircles it. A "moat" or trench partly encircles the crater to the west and south. This moat formed were the turbulence of the floodwaters interacting with the obstacle represented by the crater rim eroded material in front of, and along the side, of the crater. The rim was too high for the flood to overtop, and the flood lasted too short a time for the erosion to breach the crater rim and destroy it.

The crater seen here was most likely formed early in Mars history, perhaps as long as 3.5 billion years ago. Sometime after it formed by meteor impact, it was buried by the material that comprises Lunae Planum (the large plains unit of which the island appears to be part). The material composing the island is, at least in places, hard rock, since the brink of the cliff is sharp and the erosional ridges that extend down from the brink stand out in sharp relief. However, the processes that emplaced the rock were sufficiently gentle that the crater was not destroyed by that emplacement, nor by the burial. In that respect, the crater is like a giant fossil. Likewise, the process or processes that exposed the crater--the Kasei floods and retreat of the mesa scarp--were also sufficiently "gentle" so that much of the crater's original appearance has been preserved.

This exhumed crater is one of many seen by MOC during its first year of operations. This particular crater was first suspected to have been exhumed when it was seen in images from Mariner 9 in 1972. The close-up view provided by MOC confirms that the crater has emerged from beneath the mesa, and that it suffered little damage from the Kasei floods.

Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

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