Mercury

Mercury is the closest planet to the Sun and has almost no atmosphere (trace amounts of hydrogen and helium). Mercury is about the same size as our Moon. The gravity on Mercury is 38% of the gravity on Earth. Mercury has a huge range in temperatures (high temperatures at daytime - which is 88 Earth-days long and low temperatures at night) This planet has no moons. The only spacecraft to approach Mercury so far has been NASA’s Mariner 10 (1974–75).

orbit: 57,910,000 km (0.38 AU) from Sun
diameter: 4,880 km
mass: 3.30e23 kg