Alex McColgan

And while you are mostly right with that, we have found evidence that material does move on the Moon occasionally.

See if you can spot what I'm talking about in this image here as I pan across.

This is the edge of a large 32km wide crater known as Kepler crater, and what you may notice along the crater wall is evidence that landslides have occurred here, with the dark material apparently having fallen down the slope.

Let's have a closer look at what's going on by zooming in on the most prominent of the landslides in this crater.

The material seems to originate from box canyons towards the top of the crater rim.

The material coming down here is clearly very fine, certainly less than a metre across, as no individual rocks can be resolved within the slide.

However, the largest rocks that got dislodged seem to have all made it to the bottom of the crater floor.

What's interesting is that the main mass of the slide seems to actually be made up of many smaller slide masses.

Look at these individual trails here.

So it probably didn't all happen at once, but is happening over time.

The slides were likely triggered by tiny meteors striking the crater wall.

These tiny impacts and the subsequent landslides round off the edges of the crater, which is why the oldest types of crater on the Moon look so smooth compared to the freshest craters.

Here's another puzzle to try and solve.

Here we have the remarkable Messier crater.

Typically, craters are round, but not Messier crater.

It is elongated with a slit for a crater floor.

What is going on here?

The mystery continues if you zoom out a bit.

Directly next to Messier Crater are two more craters.

The one on the left seems much older than the other, as it seems to have been weathered away compared to the Fresh Impact crater on the right.