Mars Global Surveyor
Mars Orbiter Camera

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

Spring Time View of North Polar Sand Dunes


Mars Global Surveyor Mars Orbiter Camera Release:          MOC2-61a, -61b, -61c, -61d, -61e
Mars Global Surveyor Mars Orbiter Camera Image ID:         585958260.45205
545 KByte GIF image

(A) Location of new MOC image (#45205) relative to polar stereographic projection of a portion of Viking Orbiter 2 image 579b76 taken in late Northern Spring, April 1978. The Viking image covers a region 38 by 35.3 kilometers (23.6 by 21.9 miles). North is up, illumination in the Viking image is from the lower left. The MOC image is the slightly darker strip just left of center. The MOC image was taken in early Northern Spring, July 1998 (nearly 1 Mars decade after the Viking image).

139 KByte GIF image

(B) MOC image 45205, shown at 25 percent original size. As shown here, the resolution of the image is approximately 16 meters (52 feet) per pixel. The image covers an area about 1.2 kilometers (0.7 miles) wide and about 26 kilometers (16 miles) long. North is up, illumination is from the lower right.

130 KByte GIF image

(C) Same MOC image 45205 as in (B), above. Shown at 25 percent of its original size (approximately 16 meters (52 feet) per pixel), this version shows two white boxes that indicate the location of two full-resolution subframes presented below. The upper white box represents image (E), below. The lower white box represents the area shown in (D), below. North is up, illumination is from the lower right.

160 KByte GIF image

(D) MOC image 45205 subframe shown at full resolution of approximately 4 meters per pixel. The effective resolution of this image is less than the per pixel scale because the atmosphere was cloudy and the MOC has not yet been focussed. Features as small as 10-12 meters across are probably visible in this image. The picture covers an area 1.8 by 1.8 kilometers (1.2 by 1.2 miles). North is up, illumination is from the lower right. The crescent-shaped features are sand dunes that formed from winds that blew from the lower left/center.

174 KByte GIF image

(E) Another MOC image 45205 subframe shown at full resolution of approximately 4 meters per pixel. The picture covers an area 1.8 by 1.8 kilometers (1.2 by 1.2 miles). North is up, illumination is from the lower right. Like the previous image, the hills shown here are sand dunes that formed from winds that blew from the lower left/center.

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.


Spring has come to the martian northern hemisphere. The northern spring season began in mid-July 1998. With the arrival of spring comes the annual shrinkage of the north polar frost cap. Sunlight is now falling on the north polar cap, and all of the carbon dioxide frost and snow that accumulated during winter has been sublimating--going directly from solid to gas--and the surface beneath the frost is being revealed.

The MOC image shown above, 45205, was obtained during the 452nd orbit of Mars Global Surveyor at 3:10 p.m. PDT on July 26, 1998. The image is located near latitude 76.87°N, longitude 253.81°W, and it shows a close-up view of martian sand dunes. These dunes were not visible to MOC until the last week of July. Just a few months earlier, the dunes were likely covered with frost, obscured by thick clouds, and cloaked by the darkness of the martian polar winter. Indeed, small patches of bright frost were still present when the picture was taken (e.g., the bright patches on the west (left) side of each crescentic dune in (D))

As the above picture illustrates, the camera on board Mars Global Surveyor (MOC) continued to take exciting new views of the martian surface throughout July 1998. As the month progressed, the ground track-- the area visible to the camera--migrated farther north. Simultaneously, sunlight began falling on the north polar regions, making it possible to take some pictures at far northern latitudes. However, these regions have been tricky to photograph because of thick clouds and hazes. The image shown here, for example, is relatively bland gray (has relatively low contrast) because of clouds.

As first seen by the Viking 2 Orbiter in 1976, a vast "sea" of sand dunes surrounds the north polar cap. The dunes imaged by MOC (above) are classic forms known as barchan dunes--the small, crescent-shaped hills (see (D) above)--and transverse dunes--ridges that resemble coalesced barchans (shown in (E) above). These dunes are similar in size and shape to familiar sand dunes found in desert regions on Earth. These two varieties form from winds that persistently come from a single direction (in this case, from the southwest).

Over the next several months, the sky above these dunes will clear. Northern Summer will arrive near the end of January 1999, and Mars Global Surveyor should have an excellent view of this region when it begins its mapping mission in late March 1999. Because it is in a polar orbit, Mars Global Surveyor will have many opportunities to revisit the north polar dunes in 1999. The images in 1999 will have resolutions around 1.5 meters (5 feet) per pixel--a substantial improvement even over the pictures shown here.

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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