Martian Caves (edm n. 1 - possible natural colors; credits: Lunexit)

The pair of Pit Craters visible here are the smallest “anomalous” pits known to exist at this time. These have either vertical or sub-vertical interior walls (sub-vertical means that they are not visible from a nearly overhead viewing perspective), and each pit is deep enough that sunlight does not hit the floor when the Sun is at or near the Zenith.

Unfortunately, the only thermal-infrared camera currently orbiting Mars cannot resolve features this small, so the temperature characteristics of these pits must remain unknown for now, underscoring the need for a high-resolution thermal instrument on future missions.

Intriguingly, when pit craters on Earth have similar characteristics to the pair shown here, they often have cave entrances in their bases connecting to large underground networks. Current investigations are determining whether the anomalous Martian Pits may be shown to contain such entrances.