Mercury

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Note: You can click on each image below to view a larger version. Mercury, the closest planet to the Sun, is a desolate ball of rock that looks somewhat like the Moon. Since it is so close to the Sun, the surface temperature can reach 450C during the day and then fall to -170C at night. RIGHT: A picture taken by NASA's MESSENGER probe during a fly-by in January 2008. After two further fly-bys it will go into orbit around Mercury in March 2011. The only previous mission to Mercury was NASA's Mariner 10 in 1974. After MESSENGER, the next visitor will be the ESA's BepiColombo in 2019. The most prominent feature is the Caloris basin, a lava-flooded basin containing rings of concentric mountain ranges, and radiating fractures and ridges. The name is Latin for "heat", and it is called this because the Sun is directly overhead there when Mercury is at its closest to the Sun during its orbit. It appears to be the result of a gigantic meteorite impact, and is 1300km in diameter. The Bach region (from Mariner 10) The Caloris Basin (from Mariner 10) - the curved ridges shown in the picture are its outer walls There is virtually no atmosphere, other than a few traces of gas temporarily captured from the solar wind, which is a stream of electrically charged particles constantly flowing out from the Sun. Mercury does not have any moons. Mercury looks like a pinkish-orange star to the naked eye, although even the largest terrestrial telescopes can't show it as anything more than a pinkish blob with vague dark markings. Depending on where it is in its orbit, it will either rise just before the Sun, or set soon after it, so it is only ever seen low-down near the horizon, in twilight. Warning! If you ever try to see Mercury, take care not to look directly at the Sun, especially if you are using binoculars, as it would seriously damage your eyes.

		Last Updated: 25 Jun 08