Sandstone Cliffs and Hematite Lag Deposits of Ophir Mensa
NASA/JPL-Caltech/UArizona
Sandstone Cliffs and Hematite Lag Deposits of Ophir Mensa
PSP_002208_1755  Science Theme: Geologic Contacts/Stratigraphy
This target was one of the first close HiRISE views of the enigmatic Valles Marineris interior layered deposits. These light-toned sedimentary deposits are of interest to scientists because they are partially composed of minerals like hematite that likely formed in the presence of liquid water.

The lighter-tone linear units to the north are called “yardangs” and formed when downslope winds carved the fragile sandstone into channels. Over time, wind and gravity conspire to erode material downslope and onto the canyon floor. The darker-toned sandy deposits at the cliff base contain high concentrations of hematite (along with basaltic or volcanic sand) known from infrared orbital measurements.

HiRISE resolution can clearly show outcrops mass wasting finer materials out, and darker layers that are likely hematite-bearing units. This is an excellent candidate for what’s called a “hematite lag deposit,” where more resistant iron-rich hematite concretions have weathered out of the brittle mesa driven by gravity and wind, similar to that observed at the Mars Exploration Rover Opportunity landing site.

Written by: Matthew Chojnacki (narration: Tre Gibbs)  (13 November 2013)
 
Acquisition date
15 January 2007

Local Mars time
15:40

Latitude (centered)
-4.479°

Longitude (East)
287.251°

Spacecraft altitude
266.1 km (165.4 miles)

Original image scale range
from 26.6 cm/pixel (with 1 x 1 binning) to 53.2 cm/pixel (with 2 x 2 binning)

Map projected scale
25 cm/pixel and North is up

Map projection
Equirectangular

Emission angle
0.0°

Phase angle
56.0°

Solar incidence angle
56°, with the Sun about 34° above the horizon

Solar longitude
167.1°, Northern Summer

For non-map projected images
North azimuth:  97°
Sub-solar azimuth:  15.6°
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POSTSCRIPT
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.