Distinctive Rayed Impact Crater in Meridiani Planum
NASA/JPL/University of Arizona

Distinctive Rayed Impact Crater in Meridiani Planum
ESP_020784_1810  Science Theme: Impact Processes
FrançaisEspañolPortuguêsItalianoGreekArabic



WALLPAPER

800  1024  
1152  1280  
1440  1600  
1920  2048  
2560  

HIFLYER

PDF, 11 x 17 in  
This "fresh" (very well-preserved) impact crater has created a radial pattern of dark rays. The image was suggested to address the question of why the rays are dark.

Is the crater so fresh and recent that there hasn't been time for bright dust to settle on the rays? That doesn't seem likely, as we can see windblown deposits inside the crater, which requires at least thousands of years to form after the impact event. Also, fresh craters with dark ejecta are common in Meridiani, and they can't all be extremely recent.

Did the crater eject a subsurface layer of dark material? Maybe, but all of the bedrock exposures in the surrounding region are relatively bright. The surface layer is darker than the bedrock because dark materials like hematite concretions ("blueberries" found by Opportunity rover) are resistant to wind erosion and get left as a lag deposit. At HiRISE scale the rays are seen to be a thin deposit, perhaps less than 1 meter thick.

The more distant ray segments contain many small secondary craters created by impact of rocks ejected from the primary crater. Maybe these are lag deposits from the original rays. In other words, a mix of broken-up target material was deposited, but the relatively bright materials have blown away since the crater formed. The darker sand or granule-sized materials might eventually be moved by the wind and trapped inside craters, as commonly seen over Meridiani Planum, but there hasn't been sufficient time since crater formation for this process to remove the rays.

The coarser particles might not be movable by wind in the current climate regime of Mars, but that changes over thousands and millions of years as Mars experiences periodic changes in orbital parameters such as tilt of the rotational axis. There has been some sand movement since the crater formed, since we see deposits inside the crater, but not enough to remove the rays.

Written by: Alfred McEwen   (19 January 2011)



 Image Products: All image links are drag & drop for HiView, or click to download
JPEG
Grayscale: map projected  non-map
IRB color: map projected  non-map
Merged IRB: map projected
Merged RGB: map projected
RGB color: non-map projected

JP2 DOWNLOAD
Grayscale: map-projected (291.8 MB)
IRB color: map-projected (155.2 MB)

JP2 EXTRAS
Grayscale: map-projected  (148.1 MB),
non-map  (119.7 MB)
IRB color: map projected  (39.1 MB)
non-map  (151.7 MB)
Merged IRB: map projected  (83.3 MB)
Merged RGB: map-projected  (79.7 MB)
RGB color: non map-projected  (148.0 MB)

ADDITIONAL IMAGE INFORMATION
Grayscale label   Color label
Merged IRB label   Merged RGB label
EDR products

About color products (PDF)
HiView main page

 Observation Toolbox
Acquisition date:02 January 2011 Local Mars time: 3:37 PM
Latitude (centered):1.219° Longitude (East):6.130°
Range to target site:272.1 km (170.0 miles)Original image scale range:from 27.2 cm/pixel (with 1 x 1 binning) to 54.4 cm/pixel (with 2 x 2 binning)
Map projected scale:25 cm/pixel and North is upMap projection:Equirectangular
Emission angle:5.5° Phase angle:50.2°
Solar incidence angle:56°, with the Sun about 34° above the horizon Solar longitude:209.5°, Northern Autumn
For non-map projected products:
North azimuth:97° Sub-solar azimuth:349.5°
For map-projected products
North azimuth:270°Sub solar azimuth:164.4°

Context map

Usage Policy
All of the images produced by HiRISE and accessible on this site are within the public domain: there are no restrictions on their usage by anyone in the public, including news or science organizations. We do ask for a credit line where possible: Image: NASA/JPL/University of Arizona
Postscript
For information about NASA and agency programs on the Web, visit: http://www.nasa.gov. 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. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.