A Crater in Scalloped Terrain
NASA/JPL-Caltech/UArizona
A Crater in Scalloped Terrain
ESP_074757_1235  Science Theme: Glacial/Periglacial Processes
Sublimation (ice vaporizing without passing through a liquid stage) is an important process affecting water ice in the mid-latitudes of Mars. This might be responsible for creating two different landforms: scalloped depressions and expanded craters.

Scalloped depressions are oval or irregular pits with relatively steep pole-facing slopes, and expanded craters appear to be impact craters that have grown larger as the upper slopes sublimate, while dust and debris protect the bottom.

The two usually do not occur together, but here we see what appears to be a slightly expanded crater in a field of scalloped depressions. It’s possible that it will evolve over time to look more like the scallops. Unfortunately, this process is too slow to see with before-and-after HiRISE images, even if they were spaced years apart.

Written by: Colin Dundas  (18 October 2022)
 
Acquisition date
08 July 2022

Local Mars time
15:24

Latitude (centered)
-55.989°

Longitude (East)
57.176°

Spacecraft altitude
250.6 km (155.7 miles)

Original image scale range
from 25.1 cm/pixel (with 1 x 1 binning) to 50.3 cm/pixel (with 2 x 2 binning)

Map projected scale
25 cm/pixel and North is up

Map projection
Equirectangular

Emission angle
4.7°

Phase angle
44.1°

Solar incidence angle
48°, with the Sun about 42° above the horizon

Solar longitude
261.9°, Northern Autumn

For non-map projected images
North azimuth:  98°
Sub-solar azimuth:  25.5°
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Black & white is 5 km across; enhanced color about 1 km
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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-Caltech/UArizona

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.