Lunar Features

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Look at the full moon with the unaided eye, you might think that it is a sister planet to that 'pale blue dot' our own Earth.  The moon seems to have blue seas like Earth, and there are large expanses of white that could be cloud masses.

In fact those huge 'seas' are really huge lava flows called maria and the white 'clouds' are the lunar land masses or terra covered with dust and debris known as regolith.

Look through a telescope, and you will find that the terra is a jumble of craters, but the maria seem to be smooth and rimmed by what appears to be mountains.  In fact those maria are themselves huge craters called impact basins that filled with lunar lava.  The mountains that you see are in fact the impact basin rims.

The crater Eratosthenes lies at the end of the Apennine mountain range. The Apennines are really the eastern rim of the impact basin known as Mare Imbrium.

You can easily see the crater's central peak and terraces in the inner crater wall. These are artifacts of the impact. At the point of impact, the compacted and melted lunar surface rebounds to create the peaks. Terracing is caused by slumping of the material excavated from the impact. Lunar north is at is at the top of this photo.

Early observers of the moon gave lunar features rather exotic names - Marsh of Decay, Sea of Serenity, and so forth.  Many of those names are still in use today, in their original Latin forms.

The table below includes lunar features names in both Latin and English.  The left column lists feature types, such as seas and faults.  The right collumn lists the major lava plains.  Some of these maria and there associated montes or rims are mapped out in the Lunar Map Section.

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