Learn

Mars

Genuinely red to the naked eye, and the only planet whose surface you can see from a back garden.

Seeing it from the UK

Easily seen with the naked eye as a distinctly orange point, and the colour is the giveaway. How bright it is changes enormously depending on where the two planets are in their orbits, so some years it outshines everything except Venus and Jupiter, and in others it is unremarkable. A small telescope will show the polar cap and the darker markings when Mars is close, which happens roughly every two years and two months. In between it is a small orange dot and there is not much detail to be had.

Mars is about half the width of the Earth and has roughly the same land area, because it has no oceans. The colour is not a trick of the camera. The dust really is rust, iron oxide, and it covers almost everything, which is why it looks orange even without a telescope.

It has the largest volcano in the solar system, Olympus Mons, which is about two and a half times the height of Everest and so wide that standing on it you would not be able to tell you were on a mountain at all. It also has a canyon system that would stretch across the whole of the United States.

Both polar caps are real ice and they grow and shrink with its seasons, which last about twice as long as ours. Some of that ice is water and some of it is frozen carbon dioxide, which turns straight back to gas in the Martian spring.

The numbers

Distance from the Sun: About 142 million miles, half again as far as us
A day there: 24 hours 37 minutes, very close to ours
A year there: 687 Earth days
Moons: Two, Phobos and Deimos, both small and lumpy
Tallest volcano: Olympus Mons, around 22km high
Why it is red: Iron oxide dust, which is rust, over almost the whole surface

To find out whether it is up tonight, and when it gets properly dark where you are, see Sky Tonight.