Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System after Mercury
Mars is a cold desert world half the size of Earth. Mars is sometimes called the Red Planet. It's red because of rusty iron in the ground.
Like Earth, Mars has seasons, polar ice caps, volcanoes, canyons, and weather. It has a very thin atmosphere made of carbon dioxide, nitrogen, and argon.
There are signs of ancient floods on Mars, but now water mostly exists in icy dirt and thin clouds. On some Martian hillsides, there is evidence of liquid salty water in the ground.
Scientists want to know if Mars may have had living things in the past. They also want to know if Mars could support life now or in the future.