Mercury

picture : False Colour Image of Mercury taken from Bill Arnett's The Nine Planets

Introduction

Mercury is the innermost planet of the solar system. Its close proximity to the Sun makes the surface extremely hot (about 425 celsius) on the sunward-facing side, but this is balanced by a relatively cool (about -185 celsius), shaded, outward-facing side. It rotates much more slowly than the Earth, one day being about the equivalent of 88 Earth days. This means that there are three days every two years on Mercury. The sun's proximity also makes Mercury difficult to observe from the Earth, since it is usually in the sky during the day only. Occasionally though, it is visible in the lower reaches of the sky as a small crescent.

Missions to Mercury

Several probes have been launched towards Mercury. The most famous of these was Mariner 10 (NASA) which was used to study this small planet in the early seventies. Mercury turned out to be quite bland compared to other bodies in the solar system, its surface being inactive, rocky and highly cratered. Amazingly though, due to the heating effect of the nearby sun, Mercury has been observed to have small quantities of water ice housed in the protection of some craters. It had been expected that any water on the planet would have long since boiled off.

After a respite spanning decades, a new probe named Messenger is on its way to study Mercury. Expected to make its first flyby of the planet in June 2008, Messenger is run jointly by NASA, the Carnegie Institution, Washington, and the Johns Hopkins University, Maryland.