Mercury is the closest of the planets to the sun. The volume of mercury is 0.056 times the volume of earth. Its density is 5.43 times the density of water. Its mass is 0.055 times the mass of earth. Tiny mercury is only a third of the size of the earth. Mercury is only slightly bigger than our moon. It has almost no blanket of atmosphere around it to protect it from the sun’s rays, or keep the warmth in, at night. There is never any gust of wind or drop of rain. There are no clouds or colours in the sky. Mercury has a thin, rocky crust, with a large metallic core, probably made of iron, at its centre. Mercury is covered with craters and has ice at its poles. A crater is the round ‘scar’ left by a meteorite smashing into a planet, just like a pebble thrown into the sand. Mercury’s landscape is blasted with huge craters made by meteorites that showered the planet millions of years ago. Mercury has an extremely thin atmosphere of helium and hydrogen captured from the solar wind. Mercury average distance from the sun is 58 million kilometres. Mercury is about 4878 kilometres across. Temperatures on mercury’s surface can reach up to 400 degrees Celsius. Nighttime temperatures on the surface can drop far beyond minus 170 degrees Celsius. A day on Mercury is 59 earth days long. Mercury travels around the sun every 88 earth days. Mercury does not have any moons.