On a clear night, Mars can look like a tiny orange ember hanging in the sky. People noticed that color thousands of years ago. The ancient Egyptians called it Her Desher, "the red one," and the Romans named it after Mars, their god of war.
So what makes a whole planet red? The answer is something you might find on an old bike left out in the rain.
Mars is the fourth planet from the Sun and looks red because of rusty dust.
A planet covered in rust
Mars is rich in iron. When iron reacts with oxygen, it turns into iron oxide, better known as rust. On Mars, rusty minerals coat the rocks and soil, and the fine, powdery dust is full of them. That dust gives the planet its famous reddish-orange glow.
The dust is so fine that the wind lifts it high into the thin air, which is why the Martian sky looks hazy and reddish during the day. At sunset, the dust plays a trick: the sky around the setting Sun glows blue, the opposite of what we see on Earth.
How Mars got so rusty is still being studied. In 2025, scientists using data from European and NASA spacecraft suggested the dust may contain ferrihydrite, a kind of rust that forms when cool water is around. If they are right, Mars rusted long ago, while it still had water on its surface. You can read more on ESA's website.
Red on the outside, gray underneath
Here's the twist: Mars is red mostly on the surface. When NASA's Curiosity rover drilled into Martian rocks, the powder that came out was gray. The rusty layer is more like a coat of paint than the color of the whole planet.
About 70 percent of Earth's surface is covered by water.
Earth has plenty of iron too, but oceans, plants and weather keep reshaping our planet's surface. From space, Earth looks blue and white, while dry, dusty Mars keeps its rusty coat.
Olympus Mons: a volcano off the scale
Mars is only about half as wide as Earth, yet it holds the biggest volcano known in the solar system. Olympus Mons rises more than twice as high as Mount Everest, and NASA says its base would cover the US state of Arizona.
It's a shield volcano, the same type as the volcanoes of Hawaii, with gentle slopes that stretch for hundreds of kilometers.
How long is a day on Mars?
Almost the same as ours, which surprises a lot of people. Mars spins once every 24 hours and 37 minutes, and a full sunrise-to-sunrise day, called a sol, lasts about 24 hours and 40 minutes. Rover teams on Earth have sometimes lived on "Mars time," starting work about 40 minutes later each day.
A year is another story. Mars takes 687 Earth days to circle the Sun, so a Martian year is nearly two of ours.
Quick Mars facts to share at dinner
- Mars is the fourth planet from the Sun.
- It has two small, potato-shaped moons: Phobos and Deimos.
- Gravity there is a little over a third of Earth's, so you could jump much higher.
- Dust storms on Mars can grow big enough to wrap around the whole planet.
- Every visitor so far has been a robot, carried there by a rocket.
Rockets fly up by pushing hot gas down very fast.
In Spinbo, Mars sits on the Space wheel next to the Sun, the Moon, Earth, Saturn and a rocket, in the Deep Space world with its own starry sky and music. Tap or flick the wheel, and when Mars comes up, you'll hear its name and one clear sentence in your language, then in a second language you choose.
Who knows? Your next spin might land on Saturn, and that's a whole other story.
