A Fading Impact Crater
NASA/JPL/UArizona
A Fading Impact Crater
ESP_027806_1700  Science Theme: Aeolian Processes
This cluster of craters formed quite recently from a weak impactor that broke apart in Mars’ thin atmosphere before smashing into the surface. It was discovered by the MRO Context Camera (CTX) Team, who found a dark spot in a CTX image taken in August 2008 that was not present in earlier Mars Odyssey Mission THEMIS images from July 2005. HiRISE examined the feature in October 2008 and verified that the dark spot was impact ejecta excavated from beneath the bright surface.

On June 25 2012, HiRISE took another look at the young crater to see how it had fared after two Martian years. This image was timed to closely match the illumination and viewing conditions of the earlier HiRISE image. A comparison of the two images shows that the dark halo surrounding the crater cluster has nearly vanished. The delicate rays extending beyond the halo are also significantly faded. Only the individual craters remain distinctly dark in the new image.

This observation is important for two reasons. First, it raises questions about the Martian winds and sediments that produce such changes. Did the dark ejecta blow away, or was it buried by a layer of bright dust? Second, it tells us that the window for detection of these young craters can be very short. In this case, the dark spot that drew the attention of the Context Camera Team was the 200-meter diameter halo of ejecta that encircled the crater cluster. After two Martian years, the halo is gone and the impact cluster would not be easily detected.



Written by: Paul Geissler (audio by Tre Gibbs)  (18 July 2012)
 
Acquisition date
02 July 2012

Local Mars time
15:28

Latitude (centered)
-9.725°

Longitude (East)
181.384°

Spacecraft altitude
264.3 km (164.2 miles)

Original image scale range
26.5 cm/pixel (with 1 x 1 binning) so objects ~79 cm across are resolved

Map projected scale
25 cm/pixel and North is up

Map projection
Equirectangular

Emission angle
3.1°

Phase angle
56.0°

Solar incidence angle
58°, with the Sun about 32° above the horizon

Solar longitude
133.2°, Northern Summer

For non-map projected images
North azimuth:  97°
Sub-solar azimuth:  33.9°
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non-map           (225MB)

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non map           (191MB)
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HiView

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IRB: infrared-red-blue
RGB: red-green-blue
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Black & white is 5 km across; enhanced color about 1 km
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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.