A Field of Secondary Craters
NASA/JPL/UArizona
A Field of Secondary Craters
PSP_002281_2115  Science Theme: Impact Processes
This observation shows a secondary crater field, which form when material ejected from a larger impact event impacts the Martian surface. One impact event, depending on the size of the impactor, can form hundreds of millions of secondary craters at essentially the same time.

Primary craters (those created directly from an impactor from space) can be the same size as secondary craters, which makes dating surfaces based on the number of accumulated craters difficult to near-impossible. Secondary craters are distinguished from primaries based on their morphologies. They are sometimes irregularly shaped, as seen in this image, because they form at relatively low velocities. The velocity of the impactor determines a crater’s size, shape, and depth, with lower energy impacts forming shallow, less-developed craters and higher energy impacts forming deeper, more regular craters.

Secondary craters often occur in clusters, as seen here, as a piece of ejecta breaks up before hitting the surface. Primary craters form at random locations globally. Secondary clusters are more likely to be found in groups because of their formation mechanism.



Written by: Kelly Kolb  (7 February 2007)
 
Acquisition date
21 January 2007

Local Mars time
15:34

Latitude (centered)
31.076°

Longitude (East)
89.738°

Spacecraft altitude
291.1 km (180.9 miles)

Original image scale range
29.1 cm/pixel (with 1 x 1 binning) so objects ~87 cm across are resolved

Map projected scale
25 cm/pixel and North is up

Map projection
Equirectangular

Emission angle
0.3°

Phase angle
57.1°

Solar incidence angle
57°, with the Sun about 33° above the horizon

Solar longitude
170.2°, Northern Summer

For non-map projected images
North azimuth:  97°
Sub-solar azimuth:  349.4°
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non-map           (385MB)

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non-map           (276MB)

Merged IRB
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RGB color
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ADDITIONAL INFORMATION
B&W label
Color label
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EDR products
HiView

NB
IRB: infrared-red-blue
RGB: red-green-blue
About color products (PDF)

Black & white is 5 km across; enhanced color about 1 km
For scale, use JPEG/JP2 black & white map-projected images

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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:
NASA/JPL/University of Arizona

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.