In September 1976, NASA's Viking 2 lander touched down on a
rocky plain in Utopia Planitia
near 48.0°N, 225.7°W. Utopia is a vast and varied region.
Nearly 1,700 kilometers (~1,060 miles) west of the Viking
2 site lies a pitted and fractured plain unlike anything found by the
Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) elsewhere on Mars.
Although the martian northern plains are often considered to be "flat"
or "featureless," the MOC has shown that, at the scale of a few tens of
meters (tens of yards), these plains aren't all flat, featureless, or
even "boring". In the 2001 MOC image shown here, a suite of
sharply-oulined pits and fractures
indicate that the upper surface materials are strong and indurated
(cemented). The parallel and polygonal alignments of fractures and pits
indicate that this area has been subjected to directional stress--perhaps
weaker but not unlike the stresses in the Earth's crust that cause
faulting and earthquakes. The pits furthermore indicate that something
has been removed from beneath the rigid, upper crusted material.
Unfortunately, the image does not provide obvious or direct answers
as to what the rigid, indurated upper surface is made of, nor the
composition of the material underneath it that
was removed to cause the pitting. Some
Mars scientists have speculated that removal of ground ice could cause
the pitting, but whether this is actually the case is unknown and
cannot be known with any certainty from the photograph alone.
Sunlight illuminates the scene from the lower left; the box at the
upper right shows the location of the high resolution view in Utopia.
Image Credit: NASA/JPL/Malin Space Science Systems