Mercury, photographed by the Messenger spacecraft on 8 October 2008 during a flyby of the planet. The large crater below centre is named Kuiper. Several other ray craters are evident.
Credit NASA/JHUAPL/Carnegie Institution of Washington/Galaxy

Amazing fact!

Mercury rotates very slowly, so its ‘day’ is 59 Earth days long! Yet Mercury’s ‘year’ (the time it takes to rotate around the Sun) is only 88 Earth days long. For every two Mercury years, it has only three days!

About Mercury

The closest planet to the Sun is little Mercury. It is a rocky planet, grey and covered in craters. In fact, it looks a little bit like the Moon.

Mercury is the smallest proper planet in the Solar System, at just 3,476 kilometres wide. Some scientists think that it used to be larger, once upon a time, but that it had a collision with another small planet. The collision destroyed the other planet and ripped off Mercury’s outer layers. This would have taken place over four billion years ago.

If you like sunbathing, Mercury is the place to be. Because Mercury is so close to the Sun, the side facing the Sun can get very hot, up to 430 degrees Celsius. However, the side facing away from the Sun gets very cold, as low as –180 degrees Celsius. Brrr!

NASA’s Mercury MESSENGER spacecraft spent four years orbiting Mercury and took some amazing close-up photographs of its surface, like the pictures shown on this page. You can find others here

Scarp feature (far right) on Mercury, extending for several hundred km. These features are believed to be caused by shrinkage of the planet over time.
Credit NASA/JHUAPL/Carnegie Institute/Galaxy

Mercury is covered in loads of impact craters, just like our Moon. In the image above you can see a large crater in the bottom left that has suffered other impact events on top of it. You may also be able to see a ridge running through the largest crater and one of the craters inside that. The bright, white material in the top of the image is material that has been thrown across the surface in a really big impact event.

The image below shows a double ring crater, and, if you look closely, you should be able to see chains of smaller craters spreading out from the main crater, which were formed when rocks were thrown out of the crater.

The crater Brahms on Mercury, 95 km diameter.
Credit JPL/Galaxy

Click on each of the images below to find out more about that Solar System object!