Lunar+pit

Researchers found that shadowed areas of a pit (pictured above) in the Mare Tranquillitatis region stay consistently cool during the day and night. The pit likely leads to a similarly temperate lava cave.

Researchers found that shadowed areas of a pit (pictured above) in the Mare Tranquillitatis region stay consistently cool during the day and night. The pit likely leads to a similarly temperate lava cave.
Photo NASA/GSFC/Arizona State University