By: Boston Williams
Mercury is the first planet from the Sun. It is the smallest and closest to the sun of the eight planets in the Solar System. Its distance from the Sun varies between 0.31 and 0.47 Astronomical Units. The distance from the sun is 35,980,000 miles (57,910,000 km.) The length of the day is 58d 15h 30m. The amount of gravity Mercury has is 3.7 m/s².
mass and diameter
Mercury's mass is 328.5E21 kg (0.055 Earth mass). The radius is 1,516 miles (2,440 km). The diameter of mercury is 3,032 miles (4,879 km). Mercury's size compared to other planets is (2,440 km/ 1,516 miles) -38% the size of Earth.
Mercury has no moons at all. Mercury's temperatures can go between -279 Fahrenheit (-173 Celsius) at night to 801 Fahrenheit (427 Celsius) during the day. Mercury's atmosphere contains small amounts of hydrogen, helium, and oxygen. It also has even tinier amounts of sodium, potassium, calcium, and magnesium. The surface of Mercury is marred by an impressive number of craters. The cratering is deeper than on most terrestrial planets because of its lack of an atmosphere. A thicker atmosphere would have slowed impacting bodies, making the craters more shallow.
Visits by spacecraft
Two spacecraft have visited the planet Mercury so far. The first was called Mariner 10. During 1974 and 1975, Mariner 10 flew by Mercury three times and mapped about half of the planet's surface. Mariner 10 also discovered Mercury's thin atmosphere and detected its magnetic field. More recently, Messenger went into orbit around Mercury in 2011, and completed mapping of 100% of Mercury's surface in 2013. BepiColombo is planned for launch in 2015 and planned to enter orbit around Mercury in 2022.
Fun Facts about mercury
Mercury is the most cratered planet in the Solar System
Mercury is named for the Roman messenger to the gods
The orbit of Mercury is an ellipse rather than circular.