Mercury
No one knows who discovered Mercury. Mercury is the closest planet to the sun and it also very small. The sun is 29 million miles away from Mercury. If someone were to stand on the very hot surface of mercury, the sun would appear 3 times as big as it appears from Earth. It takes Mercury 88 days to make a full orbit around the sun. That means that if humans could live on Mercury they would have a birthday every 88 days. Mercury's surface resembles that of Earth's moon. It has large craters like Earth's moon.