The Bedrock Riddles of Nili Fossae
The Bedrock Riddles of Nili Fossae
ESP_060064_2005  Science Theme: Geologic Contacts/Stratigraphy
This image of the Nili Fossae region, to the west of the great Isidis basin, shows layered bedrock with many impact craters.

Nili Fossae is one of the most mineralogically important sites on Mars. Remote observations by the infrared spectrometer onboard MRO (called CRISM) suggest the layers in the ancient craters contain clays, carbonates, and iron oxides, perhaps due to hydrothermal alteration of the crust. However, the impact craters have been degraded by many millions of years of erosion so the original sedimentary, impact ejecta, or lava flows are hard to distinguish.

The bright linear features are sand dunes, also known as “transverse aeolian dunes,” because the wind direction is at ninety degrees to their elongated orientation. This shows that the erosion of Nili Fossae continues to the present day with sand-sized particles broken off from the local rocks mobilized within the dunes.

Written by: John Bridges (audio: Tre Gibbs)  (3 September 2019)

This is a stereo pair with ESP_052389_2005.
Acquisition date
20 May 2019

Local Mars time

Latitude (centered)

Longitude (East)

Spacecraft altitude
279.7 km (173.8 miles)

Original image scale range
56.6 cm/pixel (with 2 x 2 binning) so objects ~170 cm across are resolved

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50 cm/pixel and North is up

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Phase angle

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

Solar longitude
27.9°, Northern Spring

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North azimuth:  97°
Sub-solar azimuth:  357.7°
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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.