Mercury is shrouded in a thin atmosphere of helium and argon. Its large core of iron and nickel is surrounded by a mantle and a rocky crust.
The first pictures of the surface of Mercury were drawings made by the astronomer Antoniadi in the 1920's, showing light and dark areas. More detailed images were not available until the space_probe Mariner 10 reached the planet. On the pictures take by the probe, the surface of Mercury appears covered in craters. These show that the surface is covered in numerous craters, which were probably formed by impacts during the early era of the solar system about 4 million years ago. After the planets had formed, debris left over from the formation period collided with Mercury and gave it its distinct features. At the same time, its core shrank, which made the surface appear even more wrinkled.
The largest crater on Mercury is called the Caloris basin. It is 1300 kilometers wide and two kilometers deep. It was probably caused by the impact of an asteroid of a diameter of between 100 and 150 kilometers. The shock waves created a mountain range with peaks of over 2000 meters in height in an area far away from the actual impact zone.
All the craters of Mercury have been named after famous artists. Such lyrical names as Vivaldi, Mozart and Bartok, Monet, Renoir and Rubens, but also Heine and Shakespeare can be found here. With its 625-kilometer diameter, Beethoven is the second largest ring formation after the Caloris basin.
