Mars Global Surveyor
Mars Orbiter Camera

Mars Orbiter Camera (MOC) High Resolution Images:
Seepage and Ponding within a Southern Hemisphere Crater


Mars Global Surveyor Mars Orbiter Camera Release:          MOC2-49a, -49b, -49c
Mars Global Surveyor Mars Orbiter Camera Image ID:         567897575.7707
298 KByte GIF image

(A) Regional context of MOC image 7707 (composite of Viking Orbiter 2 images 497B46-497B49), shown at a scale of 400 meters (1312 feet) per pixel.

148 KByte GIF image

(B) Mosaic of Viking Orbiter 2 images 497B47 and 497B48 shown at a scale of 200 meters (656 feet) per pixel. Crater has a diameter of 50 km (31 miles). Box shows location of MOC image 7707 (image C, below).

1.1 MByte GIF image

(C) MOC image 7707 (subframe) reproduced at full resolution, about 24.5 meters/pixel (80.4 feet/pixel).

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.

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(A) Portions of Viking Orbiter 2 images 497B46-497B49, taken in January 1978 during the Southern Autumn season, are mosaiced here to show the regional context of MOC image 7707. In this mosaic, light areas are covered with early, seasonal frosts. The four images were transformed into a polar-stereographic map projection with a resolution of 400 meters (1312 feet) per pixel. North is to the top, illumination is from the upper right. The box shows the location of crater seen at a factor of two better resolution in (B). The large, unnamed crater centered in the box is located at about 65°S, 15°W and is 50 km (31 miles) in diameter.

(B) Unnamed crater seen in MOC image 7707. Crater has a diameter of 50 km (31 miles). Polar stereographic projection with resolution 200 meters (656 feet) per pixel. North is toward the top of this image and the illumination is from upper right. Box shows location of the MOC image.

(C) MOC image 7707 (subframe) reproduced at full resolution, about 24.5 meters/pixel (80.4 feet/pixel). Picture shows an area approximately 25.1 x 31.3 km (15.6 x 19.5 miles) in size. Sun illumination is from the lower left. The MOC image is centered near 65.1°S latitude, 15.1°W longitude. Image was obtained during the Southern Spring season on December 29, 1997, at 1:19 p.m. PST on Mars Global Surveyor's 77th orbit around Mars.

Despite evidence of catastrophic floods and integrated valley networks on Mars, unequivocal evidence of ponding has been difficult, if not impossible, to find. MOC image 7707 shows what, at first examination, appears to be such evidence. There are two striking geomorphic attributes of the crater shown in the image:

  1. The crater wall shows channeling suggestive of fluid seepage.

  2. The contact (i.e., the boundary between two types of geologic materials) between the dark floor materials and the lighter materials of the crater wall suggests, by the formation of bays and peninsulas, a ponding relationship.

These relationships are best and most easily explained if, at some time in the past, water seeped out of layers within the crater wall and flowed down into the crater, flooding part of the crater floor. In this interpretation, the dark material may be sediment transported by the seeping water. The appearance of dunes within the crater may be coincidental, or the sand may have been generated by wind and wave action. The lack of superimposed fresh impact craters suggests this process may have been active relatively recently.

It is important to note that both the channel and floor relationships seen in this image may be formed by other processes, and that there is also the possibility that they may not be related (i.e., that the fluid from the channels did not emplace the dark, ponded floor material). It is also important to remember that a fluid other than water, for example, fluid lava, could be responsible for the features seen. Indeed, lower resolution Viking and some MOC images suggest just such an alternative explanation. The absence of craters may reflect the difficulty of the materials to preserve such features, or their burial by dust. Finally, the environmental difficulties of having liquid water seeping from the wall of a south polar crater are quite formidable. For these reasons, caution must be exercised in adopting any specific hypothesis.

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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