The Ghosts of Mare Fecunditatis

A gentle topographic high marks the location of an ancient crater rim in Mare Fecunditatis (7.8°S; 51.3°E). NAC frame M146662326L, illumination is from the east, north is up, image is ~1 km wide [NASA/GSFC/Arizona State University].

Today's Featured Image focuses on ancient craters that predate mare basin flooding, and which are often recognized by subdued, sometimes discontinuous circular patterns best seen near local lunar sunrise and sunset (high solar incidence as measured from the surface normal). These circles mark the locations of once majestic excavations in the lunar crust. However the emplacement of volcanic deposits filling, surrounding, and overtopping the rims have buried these ancient craters in many instances. The presence of the near-surface rims produce local stresses in the deposits, which in turn deform the mare layers. The result is a wrinkle ridge-like topography with a circular pattern. They are thus often referred to as "ghost" craters, and can be found haunting many large, basin-filling mare deposits.

WAC mosaic centered on the Featured Image location. Note second prominent ghost crater in the southeast corner of the frame. North is up, width is ~120 km [NASA/GSFC/Arizona State University].

At least two large ghost craters can be found here in the Mare Fecunditatis basin just south and southwest of the crater Ibn Battula. Some portions are simply unrecognizable as former crater rims without the large scale mosaic for context (see example below).
Another portion of the crater rim gives a muted appearance like that of a snow-covered park bench. Width is ~700 m wide [NASA/GSFC/Arizona State University].

Examine the full NAC frame to see a greater length of crater rim. Another example of a ghost crater is presented in Ghost Crater in Southern Mare Crisium. Contrast the appearance of a ghost crater to that of a flooded crater (e.g., as in Balcony Over Plato).



Posted by James Ashley on October 31, 2012 09:00 UTC.