Mercury is a planet of the Solar System, lying at 36 million miles (57.9 million Km) away from the Sun; the closest, followed by Venus. It has a rotational period around the Sun of 88 days. The surface of Mercury is rough and full of craters; not only is it the nearest to the Sun, but also the smallest planet of the system, with a diameter of 3,000 miles (4,800 km). On its surface, daylight temperature goes up to 450º C (800º F). The planet can only be seen with the naked eye shortly before sunrise.