Mars: The red planet

This is Mars, the fourth planet from the sun, and the second smallest planet of the solar system. Mars orbits the Sun at an average distance of 225 million kilometers, about 50% further from the sun than Earth. This larger orbit means it takes longer for Mars to get around the Sun. A year on Mars lasts almost twice as long as a year on Earth — 687 Earth days. As Mars goes around the sun, it experiences different seasons.

This is because its axis of rotation is tilted in relation to its orbit. One full rotation around its own axis takes Mars 24 hours and 37 minutes. So a Martian day is about the same length as an Earth day. Mars is about half the size of Earth, so its gravitational pull is smaller — about 2.5 times less. That’s still enough to keep two small rocky moons orbiting around — Phobos, and Deimos.

Mars is a rocky, or terrestrial, planet. Its dense core is made mostly of iron and nickel. The core is surrounded by a rocky mantle. A solid rocky crust that covers the mantle is between 24 and 72 km thick, and rich in iron. When iron in the crust is exposed to oxygen, the two elements bond, forming iron oxide — rust.

This gives the planet its reddish colour and its nickname: the red planet. Scientists believe that the planet might have had a protective magnetic field in its early years, which later disappeared. Without the magnetic field, and with low gravity, the layer of gases surrounding the planet — its atmosphere — has been slowly stripped away. The remaining atmosphere is very thin. It consists almost entirely of carbon dioxide, with small amounts of argon, nitrogen, and other gases.

The thin atmosphere doesn’t trap heat, which results in great changes in temperature. The air temperature swings between about −140 °C at the polar ice caps during winter and 35 °C at the equator during summer. Daytime and nighttime temperatures can vary by as much as 60°C. The varying temperatures lead to very strong winds. High speed winds pick up dust from the surface, causing the most powerful dust storms in the solar system.

The surface of Mars is marked by a network of valleys. Scientists believe they might have been formed by rivers, which would mean there used to be liquid water on Mars. Now, however, there is very little water on Mars, and virtually all of it is in the form of polar ice caps or frozen under the surface. Mars’s southern and northern hemispheres are very different from each other. The crust of the southern hemisphere is much thicker than in the northern hemisphere, which results in higher elevation.

The northern hemisphere consists mainly of low-elevation plains. But it also has the largest volcano in the solar system — Olympus Mons. It is approximately the size of Poland, and three times higher than Mount Everest! Mars also has one of the largest canyons in the solar system, Valles Marineris. It’s 4000 km long, and four times as deep as the Grand Canyon on Earth.

Mars is one of the best studied planets in our solar system. Its solid rocky surface, proximity to the Earth, and thin atmosphere have made it possible to send multiple probes and rovers to the red planet. As of 2021, two Martian rovers, along with a small drone-like helicopter, are exploring Martian geology and climate, and collecting data for scientists to investigate. Who knows what mysteries of the red planet are yet to be discovered?