Moon shiver

IT’S Earth’s closest neighbour, but what do we really know about the moon? In his monthly column, Oldham astronomer Dion Heap looks for answers.

When you look at the moon, the first thing that becomes apparent is that it has light and dark patches.

It has been volcanic — the dark, smooth areas you see are the cooled flows of lava.

In ancient times, these were thought to be bodies of water. The Latin name for them is “maria” which translates to “seas” obviously being rather flat areas.

It was one of these that was chosen for the moon landing, the sea of tranquility.

The craters give lots away as well, the moon’s outer surface material is called regolith, which darkens over prolonged exposure to the atmosphere and radiation of space, a process that takes millions of years.

But when an object has struck the moon, it throws up ejecta from deep within the surface, which is unexposed regolith.

So if we look at the craters and study the lighter rays we get a rough estimate of the age of craters.

One of the craters with the brightest rays is called Tycho and is shown towards the bottom right of the image, this is the one that makes the naked-eye moon look a little like the end of a melon.

Tycho is one of the moon’s youngest craters — a mere 108million-years-old.

One of the most-asked questions is why doesn’t the earth have craters?

Actually it does, in fact well over 100, but many of the objects that would create craters get burned up by our atmosphere.

Because we have a weather system, water and civilisation, many of the Earth’s craters have simply been covered up over time.

The moon is also in what is known as a synchronous rotation.

Meaning its rotation is synchronised with its orbit of the Earth, as a result, the same side of the moon always faces us.

Visit Dion’s website at www.astronomyshed.co.uk.