Oxia Palus Quadrangle - Layered Sediments

Layered Sediments

Oxia Palus is an interesting area with many craters showing layered sediments. Such sediments may have been deposited by water, wind, or volcanoes. The thickness of the layers is different in different craters. In Becquerel many layers are about 4 meters thick. In Crommelin crater the layers average 20 meters in thickness. At times, the top layer may be resistant to erosion and will form a feature called a Mensa, the Latin word for table.

The pattern of layers within layers measured in Becquerel crater, suggests that each layer was formed over a period of about 100,000 years. Moreover, every 10 layers can be grouped into larger bundles. So every 10-layer pattern took one-million years to form (100,000 yrs./layer X 10 layers). The 10-layer pattern is repeated at least 10 times that is there are least 10 bundles, each consisting of 10 layers. It is believed that the layers relate to the cycle of changing tilt of Mars.

The tilt of the Earth's axis changes by only a little more than 2 degrees. In contrast Mars's tilt varies by tens of degrees. Today, the tilt (or obliquity) of Mars is low, so the poles are the coldest places on the planet, while the equator is the warmest. This causes gases in the atmosphere, like water and carbon dioxide, to migrate poleward, where they turn into ice. When the obliquity is higher, the poles receive more sunlight, and those materials migrate away. When carbon dioxide moves from the poles, the atmospheric pressure increases, maybe causing a difference in the ability of winds to transport and deposit sand. With more water in the atmosphere, sand grains deposited on the surface may stick and cement together to form layers.

This study was done using stereo topographic maps obtained by processing data from the high-resolution camera onboard NASA's Mars Reconnaissance Orbiter.

• Buttes, as seen by HiRISE under HiWish program. Buttes have layered rocks with a hard resistant cap rock on the top which protects the underlying rocks from erosion.

• Possible dikes and layered structures, as seen by HiRISE under HiWish program.

• Possible fault along a butte, as seen by HiRISE under HiWish program.

• Becquerel layers, as seen by HiRISE. Click on image to see fault.

• Mounds in craters showing layers are formed by the erosion of layers that were deposited after the impact.

• Crommlin Crater Layered Deposit, as seen by HiRISE. The color blue in the photo is a false color.

• Fault across layers in a mesa, as seen by HiRISE under HiWish program.

• Close-up of layers in Oxia Palus, as seen by HiRISE under HiWish program.

• Wide view of layered surface in Oxia Palus, as seen by HiRISE under HiWish program.

• Punsk Crater, as seen by HiRISE. Scale bar is 500 meters long. Click on image to see possible fine layers on floor. Image on right is an enlargement of south (bottom) wall of crater.

• Hydraotes Chaos, as seen by HiRISE. Click on image to seen channels and layers. Scale bar is 1000 meters long.

• Grindavik Crater, as seen by HiRISE. Scale bar is 1000 meters long.

• Layers in Monument Valley. These are accepted as being formed, at least in part, by water deposition. Since Mars contains similar layers, water remains as a major cause of layering on Mars.

• Layered mesas, as seen by HiRISE under HiWish program. Location in Terra Meridiani.

• Close-up of one of mesas in previous photo showing layers. Mesa may be the remains of a lake in which sediments were deposited. Picture obtained with HiRISE, under HiWish program.

• Wide-view of layers, as seen by HiRISE under HiWish program. Box shows location of next image. Dark parts of image are dark, basalt sand sitting on level places.

• Enlargement of previous image showing a fault and layers. Image taken with HiRISE, under HiWish program.