Mars Global Surveyor
Mars Orbiter Camera

Mars Orbiter Camera (MOC) High Resolution Images
SPO-2 Observations:

"Fluidized" Crater Ejecta Deposit


Mars Global Surveyor Mars Orbiter Camera Release:          MOC2-62a, -62b, -62c, -62d
Mars Global Surveyor Mars Orbiter Camera Image ID:         587090298.47903
487 KByte GIF image

(A) Regional context of MOC image 47903. The MOC image is represented by the darkened rectangular picture, which is the actual MOC image reduced to about 7.5% of its original size. The context scene is a portion of Viking Orbiter 1 image 545a08. The Viking image was taken in December 1977; the MOC image was obtained in August 1998. Note that illumination (sunlight) in the Viking image is from the lower left, but illumination in the MOC image is from the right. The crater adjacent to the MOC image has a diameter of about 9.1 kilometers (5.7 miles). The entire area shown here is about 40x40 kilometers (25x25 miles) in size. The scene is a mercator projection, north is up.

446 KByte GIF image

(B) MOC image 47903, shown at 25 percent original size. The area shown is about 10.2 kilometers (6.3 miles) wide and 39.1 kilometers (24.3 miles) long. The image as represented here has a scale of about 27 meters (89 feet) per pixel. North is approximately up, illumination is from the right. When the image was taken, it was very early in the morning at this location--the Sun had just risen and was only about 6° above the eastern horizon.

432 KByte GIF image

(C) Same MOC image 47903 as in (B), above. White box shows the location of the full-resolution subframe shown below in (D).

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(D) MOC image 47903 subframe shown at full scale of approximately 6.64 meters (21.7 feet) per pixel. The actual scale is slightly lower (i.e., more like 8 meters--26 feet--per pixel) because the MOC is currently out of focus and because this location was photographed through a thin, early morning haze. As in (B) and (C), above, north is approximately up and 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.


The Mars Orbiter Camera (MOC) onboard the Mars Global Surveyor (MGS) spacecraft continued to obtain high resolution images of the red planet into August 1998. At this time, each ground track (the portion of Mars available for MOC imaging on a given orbit) covers areas from about 40°N on the late afternoon side of the planet, up over the sunlit north polar cap, and down the early morning side of Mars to about 20°N latitude. Early morning and late afternoon views provide good shadowing to reveal subtle details on the martian surface. Views of Mars with such excellent lighting conditions will not be seen by MOC once MGS's Science Phasing Orbits end in mid-September 1998.

The image shown here, MOC image 47903, was targeted on Friday afternoon (PDT), August 7, 1998. This picture of ejecta from a nameless 9.1 kilometer (5.7 mile)-diameter crater was designed to take full advantage of the present lighting conditions. When the image was taken (around 5:38 p.m. (PDT) on Saturday, August 8, 1998), the Sun had just risen and was only about 6° above the eastern horizon. With the Sun so low in the local sky, the contrast between sunlit and shadowed surfaces allowed new, subtle details to be revealed on the surface of the crater ejecta deposit.

The crater shown here has ejecta of a type that was first identified in Mariner 9 and Viking Orbiter images as "fluidized" ejecta. Ejecta is the material that is thrown out from the crater during the explosion that results when a meteor--piece of a comet or asteroid--collides with the planet. Fluidized ejecta is characterized by its lobate appearance, and sometimes by the presence of a ridge along the margin of the ejecta deposit. In the case of the crater shown here, there are two ridges that encircle the crater ejecta--this type of ejecta deposit is sometimes called a double-lobe rampart deposit. The MOC image shows that this particular crater also has "normal" ejecta that occurs out on the plains, beyond the outermost ridge of the main, fluidized ejecta deposit.

Fluidized or "rampart" ejecta deposits have long been thought by many Mars scientists to result from an impact into a surface that contains water. The water would have been underground, and could have been frozen or liquid. According to the prevailing model, when the meteor hit, this water was released--along with tons of rock and debris--and the ejecta flowed like mud. Images with resolutions higher than those presently attainable from the 11.6 hr elliptical orbit are needed to see the specific features (such as large boulders "rafted" by the dense mud) that would confirm or refute this model. Such images may be acquired once MGS is in its mapping orbit.

MOC image 47903 was received and processed by the MOC team at Malin Space Science Systems on Monday afternoon (PDT), August 10, 1998. The image center is located at 27.92°N latitude and 184.66°W longitude, in the northern Tartarus Montes region. The "Tartarus Montes" include the small massifs seen in the lower right quarter and lower left corner of image (A), above.

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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