spacecraft.co.ukPlanet Mercury
Mercury is the smallest planet in the Earth’s solar system and the one closest to the sun. It can only be seen in early morning and in the twilight hours. This planet orbits the sun once every 88 days, but takes 59 days to rotate on its own axis. The physical appearance is similar to that of the moon with many large craters. Mercury does not have any natural satellites and the atmosphere is not conducive to any form of life due to its closeness to the extreme heat of the sun.
The interior makeup of Mercury is rocky, consisting of a metallic and silicate core. Because of these characteristics, geologists suspect that this planet is rich in iron. The crust of the planet is estimated to be 100 to 200 km thick and is covered with long narrow ridges.
Scientists believe that Mercury is about 4. 6 million years old. During this time it has been heavily bombarded with comets and asteroids, which account for the large craters that can be seen on its surface. One of these, the Caloris Basin, has a diameter of 1500 km., while the Skinakis basin is more than 1600 km across. It is important to note, however, that these estimates have been derived from what scientists can see through satellite imaging and may not be completely accurate.
The surface temperature of this planet is estimated to be about 179ºC/354ºF, yet it is believed that there is ice on this planet. This is because the dark side of the planet has extremes of below zero temperatures. The floors of some of the deep craters are so far down that it is likely sunlight never reaches these areas.
The atmosphere surrounding Mercury contains several different gases and is not very stable. The magnetic field is very strong and affects the winds around the planet causing what has been called a magnetosphere. This causes solar wind to become trapped in the atmosphere and therefore solar weathering is a big factor in the various formations on the surface.
Ancient astronomers have studied Mercury and Galileo was the first to view it through a telescope. The first space probe to come close to the planet was Mariner 10 in the mid-1970’s. The images it did send back were all of the same side of the planet. In 2004, Messenger was launched with the first flyby of the planet to occur in 2008. This is perhaps the least studied of all the planets because of the difficulties of reaching it and the heat from the sun.