NASA Mars Picture of the Day: Gullies in Terra Sirenum
Mars Global Surveyor Mars Orbiter Camera
MGS MOC Release No. MOC2-406, 29 June 2003
![]() NASA/JPL/Malin Space Science Systems |
Sending a very high resolution camera to Mars–the Mars Global
Surveyor (MGS) Mars Orbiter Camera (MOC), has resulted in some startling
discoveries about the red planet since 1997. One of the MOC discoveries,
announced three years ago in June 2000, is the presence of middle- and
polar-latitude gullies that were cut by a fluid that behaves as water
does. Since their discovery, gullies have generated considerable
discussion and debate in the Mars science community. Some speculate
that they are caused by groundwater, others suggest melting of
subsurface ice or surface accumulations of snow. Still others
debate whether the fluid was water, or something more exotic like
gaseous carbon dioxide. Regardless, thousands of MOC images
obtained since 1997 show that the gullies, while occurring at
middle and polar latitudes, do not show a particular
preference for poleward-facing slopes, as had been originally
determined from the smaller sampling available in 1999 and 2000.
Gullies tend to occur in regional clusters and they
tend to be associated with layers exposed on the walls of
craters, troughs, and valleys. This example shows gullies
in the wall of an impact crater in Terra Sirenum near 39.1°S,
166.1°W. The picture was taken on June 10, 2003, the same day
as the recent Mars Exploration Rover, Spirit, launch. The scene is
illuminated from the upper left and covers an area
3 km (1.9 mi) across.
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, California.
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,
California and Denver, Colorado.