Rills are extended crevices on the Moon’s surface.
They can run up to at least 150 miles (250 km) and over a mile (1.6 km) wide.
The thousands of rills that cut through the Moon’s terrain were probably formed from channels of molten lava.
In fluvial geomorphology on earth, a rill is a narrow and shallow incision into soil resulting from erosion by overland flow or surface runoff.
