Mars is the fourth planet from the Sun. Rusty iron in its ground makes Mars look red.

Mars is much smaller than Earth. It is about half as wide.

Mars is a cold, dry, desert world. It has seasons, like Earth.

The air on Mars is thin. It is mostly carbon dioxide. People cannot breathe it.

Today, Mars has water mostly as ice, near the poles. Long ago, liquid water was on the surface of Mars.

Gravity on Mars is weaker than on Earth. It is only about 38 percent as strong. You would weigh much less there.

A day on Mars lasts about 24.6 hours. A year on Mars lasts 687 Earth days.

Mars has two small moons. They are named Phobos and Deimos. They are lumpy, like potatoes. They are not round like our Moon.

Olympus Mons is on Mars. It is the biggest volcano in the Solar System. Valles Marineris is on Mars too. It is the biggest canyon in the Solar System.

Curiosity is a robot rover on Mars. It is about the size of a small car. It drives around Gale Crater. It studies rocks, soil and air.

Ingenuity was a small helicopter. It was the first aircraft to fly on another planet. It flew on Mars.

Words to know

• gravity: a pull
• rover: a robot car
• lumpy: not round
• desert: a dry place