Paleodunes (1 - Original NASA/MGS/MSSS b/w Frame)

Caption NASA:"A pair of MGS-MOC images shows close-up views of a Sand Dunefield that was first detected by the Viking Orbiters in the late 1970's. What is surprising about the MOC images is that they reveal a dune field unlike any other thus far seen on Mars: this one has Impact Craters on its Surface, and LOTS of them! The field of parallel Ridges North of the Dunefield is a wind-eroded material named "Apollinaris Sulci". It is possible that the Dunefield shown here was once covered by this wind-eroded material and was later exhumed. Regardless, the Dunes were somehow hardened and have been exposed as hard rock on the Martian Surface long enough for many Impact Craters smaller than a few hundred meters (such as few hundred yards) across to form. These Dunes are therefore quite ancient: one might say that this is a 'fossilized' Dunefield".