Monday, December 16, 2013

The Face of the Moon (15 December 2013)

December's full moon is not until tomorrow (17 DEC 2013).  According to data from the United States Naval Observatory, 96% of the moon's visible surface was illuminated last night.    Although this is not a particularly sharp image, many of the moon's recognizable features are visible.

Moon at 96% visibility

If we divide the moon in half from top to bottom, the left half of the moon is dominated by dark "seas" or maria (from the Latin mare for "sea").  These "seas" are actually flat plains made of dark basalt, a volcanic rock.  The Mare Tranquillitatus or "Sea of Tranquility" was the site of the Apollo 11 moon landing.
Maria of the Moon

The white areas that surround the maria are called the lunar highlands or terrae (from the Latin terra for "land"). The highlands are formed of older rock than the maria pitted with impact craters.  Some of these craters can be seen in the photograph below - especially three craters on the dark maria.  These three craters appear as bright spots on the otherwise dark basaltic surface.

Three lunar impact craters

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