Mercury is the 1st, or innermost, planet of our solar system, it is the also the smallest. Mercury’s distance from the Sun changes as it rounds its orbit. Because it is so close to the Sun, it is constantly bombarded with by solar wind.
Mercury’s surface is heavily scarred with craters, from collisions during the first hundred million years of the Solar System’s existence.
The planet is named after the god of commerce, travel and thievery from Roman mythology, the Greek counterpart is Hermes, the messenger of the Gods. The planet is most likely named this because it travels so quickly across the sky.
Mercury has been mentioned as early as the 2nd millennium BC by the Sumerians, and documented by the Babylonians, who at the time called the planet Nabu.
The one spacecraft to have visited was the Mariner 10, in 1974, which photographed half the planet. During it daytime it is is hot that lead would run like water over the rocks. But at night its surface is colder the icy planet Jupiter.
Mercury is the second densest planet, so it has a large metallic core, presumably made of iron. When heated or cooled, iron changes its size, more than rock. As the hot core cooled over hundreds of millions of years, it began to shrink, making the crust become loose and wrinkled with deep ridges. Because Mercury has virtually no atmosphere, to reflect the Sun, so the sky of the planet is black. Some of these deep ridges and craters have been in darkness for billions of years.
The smooth plains between the ridges have suggested that the planet at one time might have been volcanic. Following the formation of the Solar System lava flows would have filled in the heavily cratered areas remaining after the bombardment of the planets.
The foremost feature of Mercury is the Caloris Basin, an ancient lava filled crater approximately 800 miles across. It is suggest that is was created when a large body crashed into Mercury. The shock wave from the crash traveled around the planet and met on the opposite point, throwing up an upheaval of ridges. Mariner 10 never saw the Caloris Basin fully, due to the basin being in half darkness at the time.
The length of Mercury’s year is shorter than its day. The planets year equals 88 Earth days, but from sunrise to sunrise on Mercury takes 176 Earth days. The diameter of the planet is 3,030 miles and the surface temperature is between -300 degrees F to 800 degrees F. Mercury’s distance from the Earth is 28 million miles.