Nili Fossae has been a favorite target of HiRISE since its arrival at Mars in 2006, for many reasons, including the dramatic shape of the giant trough network and its diverse geologic materials.

In particular, the color spectrum revealed in HiRISE’s three bands is often maximized in this region due to reduced surface dust (see ESP_072554_2000 and ESP_076602_2020 ), which would, if present, scatter reflected light.

An abundance of wind-blown sand, sourced from ancient volcanic units, aids in the removal of local dust. Saltating, or “hopping,” sand is quite effective in ejecting dust and ultimately revealing local geology to orbital observations. Here, on the western rim of Nili Fossae, dark sand, likely locally sourced from wall units, collects as small dunes, which contribute to the colorful local terrains.

ID: PSP_010127_2010
date: 23 September 2008
altitude: 281 km

https://uahirise.org/hipod/PSP_010127_2010
NASA/JPL-Caltech/University of Arizona
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