9. Why do some parts of the moon and planets have more craters than others?

Only 171 impact craters have been recognized on Earth. Outside the Earth they are not so rare. If you look at the Moon, even with your naked eyes, you can see large circular spots marking its surface. Some of them may be volcanoes, like the majority of circular features on Earth. But most of them are impact craters.

Use a telescope, or a pair of binoculars, or find a map of the Moon. You will see many of these circular spots, some very large, some overlapping. The Moon’s surface is absolutely littered with them. It seems the Moon was bombarded by millions and millions of small and large objects.

Look at the beautiful maps of Mars that were made during the US and European missions to our neighbour planet (see links to ESA and NASA ). There are few places that are not covered with impact craters.

You will remember that all of the planets and their moons have been constantly bombarded since the beginning of the Solar System, billions of years ago. Now, if some surfaces show less scars than others, something must be different.

At this website you will learn about these differences and how you can find out the age of a surface by just counting the number of craters.