The features of the Moon were first mapped in the 17th century. The names of tens of thousands of craters were first
assigned then. We can introduce some terms that are used to describe the features seen on the surfaces of other worlds. Craters, of
course, are circular depressions on the surface. Here is a simulation of how they are made.
Then there are the 3 r’s:
Rays are streaks formed when material is ejected from an impact. Tycho has an extensive ray system around it.
Rilles are stream-like features apparently formed by lava flow. They are found primarily in the mare regions.
Regolith is the surface material of the Moon. It is the powdery ‘soil’ we see clinging to the boots of Apollo astronauts.
In the late 1960’s the United States sent nine human missions to the Moon as part of the Apollo program. Six of those missions landed on the surface.
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