A Crater Straddling Two Terrain Units
A Crater Straddling Two Terrain Units
ESP_035421_1810  Science Theme: Landscape Evolution
An approximately 1-kilometer impact crater located in northern Sinus Meridiani has formed along the boundary of two different terrain units. The western part of the crater has formed along a unit consisting of wind-blown basaltic materials that overlie light-toned units exposed in the crater wall.

To the east is a shallow circular depression several kilometers across that consists of multiple layers of light-toned deposits that have been eroding away. These deposits are dark in THEMIS night-time infrared and bright in day-time infrared images, suggesting that they are relatively fine grained and largely devoid of rocky materials.

Dark, fine-grained basaltic wind-blown material partially mantles these units and forms dunes throughout the region. Along the eastern rim region, the impact crater is eroding back into the terrain, forming scalloped inlets in the crater rim and re-exposing the multiple layers of light-toned deposits. Terracing is common along the eastern slope of the crater.

Turning our attention to the the western slope, we see that the rim is eroding back into the terrain more evenly. Although this slope lacks a scalloped appearance, the erosion of the top units appear to be more even and at a faster rate than the underlying light-toned deposits. Dark wind-blown basaltic dunes line the floor of the crater. Some possible explanations for the origin of these light-toned deposits are that they are altered volcanic ash or ancient lake deposits.

Written by: Ginny Gulick (audio: Tre Gibbs)  (5 March 2014)
Acquisition date
15 February 2014

Local Mars time

Latitude (centered)

Longitude (East)

Spacecraft altitude
270.8 km (168.3 miles)

Original image scale range
27.1 cm/pixel (with 1 x 1 binning) so objects ~81 cm across are resolved

Map projected scale
25 cm/pixel and North is up

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Emission angle

Phase angle

Solar incidence angle
54°, with the Sun about 36° above the horizon

Solar longitude
90.2°, Northern Summer

For non-map projected images
North azimuth:  97°
Sub-solar azimuth:  37.5°
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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.