29 Oct, 1998:
Recognizing that Mars is a desert planet, science fiction writers, scientists, and proponents of Mars exploration have,
for decades, written and talked about "The Sands of Mars". The first martian sand dunes were observed by the
Mariner 9 spacecraft in 1972. Ever since then, however, it has been unclear as to whether these dunes are active in
today's extremely thin martian atmosphere (100 times thinner than on Earth at Sea Level), or if the dunes are the
"fossil" remnants of a past epoch when the atmosphere was thicker and sand was more easily transported.
This year, the Mars Orbiter Camera (MOC), onboard the Mars Global Surveyor (MGS) spacecraft, made some key
observations that appear to indicate that some martian dunes are active today. In fact, some dunes probably
experienced activity--wind blowing the sand around--as recently as mid-1998.
Dunes typically contain granular fragments of rocks and minerals. These grains are usually 0.06 to 2 millimeters (0.002
to .08 inches) in size (which geologists call sand), and they are transported by the wind either by hopping over the
ground (a process called saltation) or rolling along the ground (called traction). Images from the Mariner 9 and
Viking orbiters of the 1970s did not have sufficient resolution to see detailed patterns of sand movement, although a
few Viking images showed faint streaks emanating from a few dune fields; these were interpreted as possible
indicators of sand movement.
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The Sands of Mars
Mars Global Surveyor has taken many images of Martian sand dunes.
Some appear to be inactive and covered with
dust. Other dunes, however, show all of the
characteristics of fresh, active dunes.
The most exciting examples, shown above, have
been found among the dunes in the martian north polar region.
More information and images from the JPL
Planetary Photojournal.
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The 1998 observations of the north polar dunes and other dune fields on Mars are quite tantalizing and appear to
indicate that many dunes are active under present martian conditions. Confirmation of this result will await the
Mapping Phase of the MGS mission, when it should be possible to take additional pictures of the same dune fields
already observed by MOC. These new pictures will be compared with the ones from 1998 to see if any changes
occurred. The Mapping Phase of the MGS mission is scheduled to commence in late-March 1999, and run for an
entire martian year, into March 2001.
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Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from
the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion
Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial
partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
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