Layers in Terby Crater
NASA/JPL-Caltech/UArizona
Layers in Terby Crater
PSP_001596_1525  Science Theme: Sedimentary/Layering Processes
This image shows a sequence of predominantly light-toned, layered, sedimentary rocks exposed by erosion on the floor of Terby Crater. Terby Crater is approximately 165 kilometers (100 miles) in diameter. It's located on the northern rim of the Hellas impact basin in the southern hemisphere of Mars.

The layered sequence is approximately 2 kilometers (1.2 miles) thick and consists of many repetitive, relatively horizontal beds. The beds appear to be laterally continuous, which means you can identify a given layer in many locations across the area.

Details in the layering seen in this HiRISE image reveal variations in the brightness of the layers and may indicate differing mineralogies. Based on the ease with which wind appears to erode these layers, they are believed to be composed mostly of fine-grained sediments. However, one or more of the beds is weathering to form meter (yard)-scale boulders that have accumulated downslope in fans of debris (see subimage). These larger boulders indicate the material in the layers may be stronger than just fine-grained sediments.

It's not clear how these layers formed, but it may have involved deposition by wind or volcanic activity. Another theory involves all or part of the Hellas Basin being filled with ice-covered lakes at one time in the past. The layers we see may have formed as material that was suspended in the water dropped down to the bottom of the lake.



Written by: Maria Banks  (10 October 2007)

This is a stereo pair with PSP_002216_1525.
 
Acquisition date
28 November 2006

Local Mars time
15:38

Latitude (centered)
-27.318°

Longitude (East)
74.283°

Spacecraft altitude
256.5 km (159.4 miles)

Original image scale range
25.7 cm/pixel (with 1 x 1 binning) so objects ~77 cm across are resolved

Map projected scale
25 cm/pixel and North is up

Map projection
Equirectangular

Emission angle
0.3°

Phase angle
68.1°

Solar incidence angle
68°, with the Sun about 22° above the horizon

Solar longitude
142.3°, Northern Summer

For non-map projected images
North azimuth:  97°
Sub-solar azimuth:  37.6°
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POSTSCRIPT
NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA’s Science Mission Directorate, Washington. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona.