Happy St. Valentine's Day from the Red Planet! The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) captured this view of a bright, heart-shaped mesa in the south polar region on November 26, 1999. Sunlight illuminates the scene from the lower left. The heart is about 255 meters (279 yards) across.

If the heart looks to you like it is a pit (negative relief) rather than a mesa (positive relief), that is because there are two effects that make this a challenging object to see. Sunlight illuminates the heart from the lower left, thus the lower left wall of the heart looks bright because it is reflecting this sunlight. The problem here is frost. Some very small amounts of residual frost are seen on the slopes facing away from the sunlight (toward the lower right and toward the top). MOC images in the martian polar regions can sometimes fool the eye because a frosted slope might at first glance seem to be a sunlit slope. This picture was taken in late southern spring in a region that spends each winter and most of each spring completely buried in bright frost.
 

This valentine from Mars is actually a pit formed by collapse within a straight-walled trough known in geological terms as a graben. Graben are formed along fault lines by expansion of the bedrock terrain.

The heart-shaped pit is about 2.3 kilometers (1.4 miles) at its widest. The graben and pit are located on the east flank of the Alba Patera volcano in northern Tharsis. This image is illuminated from the left.