What is in the dark side of the moon?

Hello friends. For centuries, astronomers have used the term dark side of the moon, to mean the part of the moon’s surface that is not currently illuminated by the sun. (This goes back at least as far as astronomer John Flamsteed in 1671.) That is still the technically correct use of the term.

A second meaning, the far side (i.e., the side facing away from Earth) first appeared in 1958 in connection with the Soviet Luna program. That year there was widespread discussion of the Soviet Union’s announced plans to send space probes to the moon, and photograph the far side.

This sense of the term is not entirely incorrect, since “dark” can also mean unseen, undetected, or unknown. However, the usage is archaic and poetical.

In the mid-1960s, science popularizer Ben Bova declared that there is no dark side of the moon, since both sides of the moon receive equal amounts of sunlight. In the 1970s astronomer Carl Sagan said the same thing.

We have plenty of pictures of the dark side of the moon, and there are only grey spots. They’re actually a lot of different things. The dark grey splotchy bit covering the top part of the moon was created as the moon formed, by molten rock (lava) cooling on its surface. They’re known as ‘lava beds’, and astronomers have named them ‘Maria’ (Latin for ‘seas’), such as the Sea of Tranquillity, which was the landing site for Apollo 11.

There’s no water in the Maria on the moon, but these areas are flatter and of lower elevation than the rest of the moon’s surface.

The whitish patches that look like spiderwebs, on the other hand, are areas of meteorite impacts from back when the Solar System was still forming. The moon acted like a shield for Earth, absorbing many impacts. Also, because of the moon’s pitiful atmosphere, a greater number of meteorites made it to the surface without burning up.

The meteor craters still exist today as no erosion forces are present on the moon.

The opposite side of the moon actually has almost no Maria on its surface. Guess the term ‘dark side of the moon’ is more of a misnomer than we thought.