Status Report

Mars Odyssey THEMIS Image: Becquerel Crater Deposit

By SpaceRef Editor

May 28, 2002

Filed under Daily Themis Pictures, Mars Odyssey THEMIS, US

Image Context:

Context image credit: NASA/Mars Orbiter Laser Altimeter (MOLA) Team

The finely layered deposit in Becquerel crater, seen in the center of
this THEMIS image, is slowly being eroded away by the action of
windblown sand. Dark sand from a source north of the bright deposit is
collecting along its northern edge, forming impressive barchan style
dunes. These vaguely boomerang-shaped dunes form with their two points
extending in the downwind direction, demonstrating that the winds
capable of moving sand grains come from the north. Grains that leave
the dunes climb the eroding stair-stepped layers, collecting along the
cliff faces before reaching the crest of the deposit. Once there, the
sand grains are unimpeded and continue down the south side of the
deposit without any significant accumulation until they fall off the
steep cliffs of the southern margin. The boat-hull shaped mounds and
ridges of bright material called yardangs form in response to the
scouring action of the migrating sand. To the west, the deposit has
thinned enough that the barchan dunes extend well into the deeply eroded
north-south trending canyons. Sand that reaches the south side collects
and reforms barchan dunes with the same orientation as those on the
north side of the deposit. Note the abrupt transition between the
bright material and the dark crater floor on the southern margin. Steep
cliffs are present with no indication of rubble from the obvious erosion
that produced them. The lack of debris at the base of the cliffs is
evidence that the bright material is readily broken up into particles
that can be transported away by the wind. The geological processes that
are destroying the Becquerel crater deposit appear active today. But it
is also possible that they are dormant, awaiting a particular set of
climatic conditions that produces the right winds and perhaps even
temperatures to allow the erosion to continue.

[Source: ASU THEMIS Science Team]

Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

NASA’s Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA’s Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

Image Credit: NASA/JPL/Arizona State University