Fans of Roddy Crater
Fans of Roddy Crater
ESP_033471_1580  Science Theme: Sedimentary/Layering Processes
Alluvial fans are found on Earth, Mars, and even Saturn’s moon, Titan. Roddy Crater on Mars is home to several large alluvial fans, which formed as water moved sediment from the mountainous crater rim and deposited it onto the flatter crater floor.

The fans built up over time during intense rain storms or from melting snow. Due to the strong winds on Mars, the river channels that once carried water and sediment on the fan surfaces are now standing as raised ridges and platforms. A thin blanket of ejecta (upper right) from a small crater on Roddy’s eastern rim protected underlying fan surfaces from modification by the wind compared to nearby, unprotected fans (left in the previous image). The scarp beneath the thin ejecta surface exposes beautiful light-toned layers from the alluvial fans below.

Written by: Sharon Wilson Purdy (audio: Tre Gibbs)  (23 July 2018)

This is a stereo pair with ESP_028579_1580.
Acquisition date
16 September 2013

Local Mars time

Latitude (centered)

Longitude (East)

Spacecraft altitude
257.2 km (159.9 miles)

Original image scale range
27.8 cm/pixel (with 1 x 1 binning) so objects ~83 cm across are resolved

Map projected scale
25 cm/pixel and North is up

Map projection

Emission angle

Phase angle

Solar incidence angle
51°, with the Sun about 39° above the horizon

Solar longitude
22.7°, Northern Spring

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North azimuth:  97°
Sub-solar azimuth:  41.2°
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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.