Mercury

Mercury orbits within the orbit of Venus at an average distance of 57.9 million km from the sun. With a diameter of 4,878 km it is only a third larger than earth’s moon, which it resembles in having a heavily cratered surface. Its ‘day’ of 58.65 days is precisely two thirds the length of its ‘year’ of 87.97 days. Daytime temperatures average 170°C. There is no atmosphere and the planet has no satellites