Rayed Crater in Elysium Planitia
NASA/JPL/UArizona
Rayed Crater in Elysium Planitia
ESP_018352_1805  Science Theme: Impact Processes
This image shows a prominent "rayed" crater in the Elysium Planitia region, the second largest volcanic province on Mars.

Rayed craters have distinct lines of ejecta emanating in all directions from their centers, creating a star-like pattern. Originally it was thought that these craters were only present on the Moon, Mercury, and some of the moons of Jupiter and Saturn, and therefore were only created on surfaces that lacked an atmosphere.

This view changed when the THEMIS camera began to image the surface of Mars and rayed craters started to become apparent in the infrared spectrum. The rays themselves are usually made up of both impact ejecta and, in the case of the larger craters, the clustering of secondary craters.

The patterns in the ground in which the crater was emplaced are composed of slightly raised sinuous ridges. These may be pressure ridges and could be the result of the expansion of cooling flood lavas prevalent in the area. Although the surface is presently covered with a light-toned dusty material, the underlying, dark presumably basaltic material is exposed in the larger craters.

This particular crater is close enough to another even larger rayed crater known as Zunil to actually be one of its secondary craters. Secondary craters generally have a shallower bottom and are often non-circular due to their lower impact velocity and angle of impact. This crater appears nearly circular with ejecta and large boulders that are visible near the crater rim and within the crater itself.

A slightly darker rayed ejecta pattern surrounds the crater and is probably composed of finer-grained material transported farther away during impact formation. The center of the crater appears to be shallower than would be expected from a higher energy primary impact event, but an elevation model would be needed to accurately measure the crater's depth to width ratio and use scaling laws to decide whether or not its a primary or secondary crater.



Written by: Shawn Hart and Ginny Gulick  (4 August 2010)
 
Acquisition date
26 June 2010

Local Mars time
15:24

Latitude (centered)
0.512°

Longitude (East)
163.138°

Spacecraft altitude
272.4 km (169.3 miles)

Original image scale range
54.9 cm/pixel (with 2 x 2 binning) so objects ~165 cm across are resolved

Map projected scale
50 cm/pixel and North is up

Map projection
Equirectangular

Emission angle
7.6°

Phase angle
48.6°

Solar incidence angle
55°, with the Sun about 35° above the horizon

Solar longitude
109.8°, Northern Summer

For non-map projected images
North azimuth:  97°
Sub-solar azimuth:  35.8°
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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.