MARS

Picture of Mars.

Mars formed about 4.5 billion years ago. It is the fourth planet from the Sun, at an average distance of 1.524 AU (about 228 million km).

Size: The diameter of Mars is about 6,779 km (roughly 53% of Earth’s). It is much smaller and lighter than Earth. Because of this, Mars has weaker gravity — only about 38% of Earth’s gravity. A person who weighs 50 kg on Earth would feel only about 19 kg on Mars.

Orbit: Mars goes around the Sun in about 687 Earth days, almost two times longer than Earth. That is one Martian year. Mars spins once in about 24 hours and 37 minutes, so one day on Mars is almost the same as on Earth. Mars is tilted by about 25°. Earth is tilted by about 23.5°. Because of this tilt, Mars has seasons just like Earth.

Temperature: On warm days near the equator on Mars, the temperature can be about +20 °C. On very cold days near the poles, it can fall to about −125 °C. The air on Mars is very thin. It is mostly made of carbon dioxide, with a little nitrogen and argon.

Magnetic field: The magnetic field of Mars is very weak. The Earth has a magnetic field because its liquid outer core is moving. Mars is much smaller: its diameter is about two times smaller, and its mass is about ten times smaller. Because Mars is small, it cooled down much faster. Its core stopped moving, so the magnetic field disappeared. After Mars lost its magnetic field, the solar wind blew away most of its atmosphere. Without an atmosphere, the water evaporated. On Mars we can still see old river channels. This means that long time ago, Mars had water.

Surface: Mars’ surface is rocky and red because of iron dust. The gravity on Mars is about two times weaker than on Earth. Mars has many mountains. One of them is Olympus Mons, and it is 22 km high. On Earth, the highest mountain is Mount Everest, and it is about 9 km high. Sometimes huge dust storms cover almost the whole planet for many weeks.

Moons: Mars has two tiny moons — Phobos and Deimos. Their names come from Greek words: Phobos means “fear,” and Deimos means “panic.” They are not round like our Moon. They look more like big rocks in space. Scientists think they might be captured asteroids. Phobos is slowly getting closer to Mars and one day may break apart.

Life: Scientists have not found life on Mars yet. But because Mars once had water, there might have been tiny life long ago. Some scientists think that small bacteria could still live deep in the soil, where it is warmer and protected from radiation.