08/02/2022 – Ephemeris – Where did the Moon’s “seas” come from?

This is Ephemeris for Tuesday, August 2nd. Today the Sun will be up for 14 hours and 37 minutes, setting at 9:07, and it will rise tomorrow at 6:31. The Moon, 3 days before first quarter, will set at 11:37 this evening.

As the days progress to full moon on the 13th, the Moon will reveal its many maria or seas, as the first telescopic astronomers called these blemishes. Many have roughly circular outlines bounded by mountains. They have flat floors that are darker than the heavily cratered parts of the moon, and have very few craters on them. That means they were created after the major craters were made, and obliterated the craters beneath. The majority of the cratering came very early, as the Moon accreted from the material the was produced when a Mars sized protoplanet hit the early Earth about 4.51 billion years ago. That’s according to most planetary scientists. The maria are actually huge craters produced by large asteroids later, about 3.9 billion years ago.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). They may be different for your location.

Addendum

Lunar “seas” seen on a first quarter moon. Mare is Latin for sea. Sinus means bay. Created using Stellarium, GIMP and LibreOffice.

Lunar “seas” and some other prominent features labeled on the last quarter moon.