If you look up at the sky on a clear night, you may see a red dot among the stars. This dot is Mars, named in ancient times after the Roman god of war. Although no one has ever visited this red planet, we know a lot about it.

Mars is more like Earth than any other planet in our solar system. Mars has a 24-hour day, a rocky crust, canyons, volcanoes, polar ice caps, and seasons. But Earth and the “4th rock from the Sun” are hardly twins.

Mars is half as big as Earth and has less gravity. It has very little atmosphere. The surface of Mars has no lakes or oceans, plants or animals. No place on Earth gets as cold as Mars. The lack of life on the surface of Mars isn’t surprising, considering the bone-dry environment.