* Rilles: These are long, narrow channels or valleys that are often formed by erosion or volcanic activity. They are common features on the surfaces of celestial bodies like the Moon and Mars, and are often found in bedrock.

* Highlands: These are elevated regions on a celestial body, not cracks in the bedrock.

* Maris: This term is Latin for "seas" and refers to large, dark, flat plains on the Moon.

* Umbra: This refers to the dark central part of a shadow, specifically the shadow of a celestial body (like the Moon) during an eclipse.

Let me know if you have any other questions!