Eroding Mesas Forming Seif and Barchan Dunes
Eroding Mesas Forming Seif and Barchan Dunes
PSP_007676_1385  Science Theme: Aeolian Processes
This observation shows sand dunes within the Hellespontus region of Mars.

The sand appears to come from the layered mesas and knobs, features that have been eroded by powerful winds. The dunes here have a morphology indicating formative winds blowing from east to west (from right to left).

The primary indicator for this is the orientation of the barchan dunes, a dune type that on Earth has its horns in the downwind direction. Also, the steepest faces of the dunes are on the dunes’ eastern side, indicating easterly winds.

In addition to the barchans, some of the dunes are organized into a “seif,” or longitudinal, form whereby their long axis is parallel to the wind. These are seen emanating from the sand sheets next to the mesas and knobs, as well as from some barchan horns.

Written by: Circe Verba and Nathan Bridges  (9 April 2008)
Acquisition date
16 March 2008

Local Mars time

Latitude (centered)

Longitude (East)

Spacecraft altitude
253.9 km (157.8 miles)

Original image scale range
51.4 cm/pixel (with 2 x 2 binning) so objects ~154 cm across are resolved

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50 cm/pixel and North is up

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Solar incidence angle
74°, with the Sun about 16° above the horizon

Solar longitude
45.8°, Northern Spring

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North azimuth:  97°
Sub-solar azimuth:  49.8°
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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.