Mars is made of rock that has lots of iron in it. The iron in the rock and soil make the planet look red. Astronauts haven't walked on Mars, but space probes have landed there. I was the first probe and it landed in 1976. They were looking for signs of life.
Some scientists think they found a kind of life form called microbes in the rock samples.
Mars has the biggest volcano in the solar system. It's much higher than the tallest volcano on earth. Mars looks like a red star in the night sky.