The innermost planet to the Sun
Mercury is the smallest of the first eight planets, with a radius around 2440 km, which is only slightly bigger than the Moon. A desolate, cratered terrestrial world with no Earth-like atmosphere, active volcanoes, moons, or life, Mercury has a rocky surface much like the Moon and is the second densest of the planets at 5.43 g/cm3
Space and Astronomy Wiki – the planets in the solar system –
Mercury is the fastest moving planet, traveling through the solar system almost 50 km (31) miles per seconds faster than any other planet. Every day is 59 Earth days long and a year – the time it takes the planet to orbit the Sun – takes only 88 days, a combination resulting in daylight temperatures reaching 800 degrees Fahrenheit (420 degrees Celsius) and a brisk night at around -290 degrees Fahrenheit (-180 degrees Celsius).
Mercury was visited by Mariner 10 during 1974-1975 and MESSENGER orbited the planet three times between 2008-2009, before going into orbit in March 2011 for an extended analysis. On Thursday, April 30, 2015, MESSENGER ended its mission by creating a new crater on the surface of Mercury.
You can learn more facts & figures about Mercury here.
Learn more about the things MESSENGER taught us about Mercury.
Learn more about the ancient sky watchers of the American Southwest.
Learn about the search for life near Jupiter.