Mars Facts for Kids
A rusty red planet with a butterscotch sky, the tallest volcano we know of, and robot explorers rolling across it right now.
Why is Mars red?
Mars is red because its dust is full of rust. Long ago, iron in the rocks joined with oxygen and became iron oxide, the same red-brown stuff that grows on an old nail left out in the rain. That rusty dust covers the ground and blows around in the air, so the whole planet looks red.
Mars is the fourth planet from the Sun, about half as wide as Earth. Its air is very thin and mostly carbon dioxide, so you could never breathe it. It is also very cold, usually far below freezing.
📏 How big is Mars?
The width of each world, from one side to the other.
- Earthabout 12,700 km
- Marsabout 6,800 km
- Our Moonabout 3,500 km
How a Mars rover works
A rover is a robot car that explores another world. It rolls on six wheels with ridges called cleats that grip the loose, sandy ground. It moves very slowly, just a few centimetres every second, because getting stuck would end the mission.
Nobody can steer a rover with a joystick. A radio message takes minutes to travel between Earth and Mars, anywhere from about 3 to 22 minutes. So the team sends a whole list of commands, and the rover carries them out on its own.
Famous Mars rovers
- Sojourner (1997) was the first rover on Mars. It was about the size of a microwave oven.
- Spirit and Opportunity (2004) ran on solar panels. Opportunity was built for 90 days and kept going for almost 15 years!
- Curiosity (2012) and Perseverance (2021) are about the size of a small car, and run on nuclear batteries instead of solar panels.
- Perseverance brought a little helicopter, Ingenuity, the first aircraft to make a powered flight on another planet.
A sky the colour of butterscotch
On Earth the daytime sky is blue. On Mars, so much fine dust floats in the thin air that the daytime sky is a pale, butterscotch tan. And at sunset it swaps around: the sky near the setting Sun turns blue.
That same dust is a problem for rovers that run on sunlight. Dust storms settle a red film over the solar panels until no power gets through. That is what finally ended Opportunity’s long mission in 2018. (Real rovers don’t carry a brush to clean themselves!)
Marvellous Mars Facts
A day on Mars is just a bit longer than ours.
A Martian day, called a sol, lasts about 24 hours and 40 minutes. But a Martian year lasts 687 Earth days.
Mars has ice caps at its poles.
They are made of frozen water and frozen carbon dioxide, which we call dry ice.
You can read a Mars rock by its colour.
Rusty red rock is full of iron. Dark grey rock is usually basalt, cooled lava. Rovers use clues like this, plus their instruments, to choose what to study.
Perseverance is collecting rock samples.
It seals its best samples in tubes and leaves some on the ground, hoping a future mission can fetch them. Rovers themselves never come home.
Mars has a canyon as long as the USA is wide.
Valles Marineris stretches about 4,000 kilometres across the planet.
Science words to know
- Rover
- A robot vehicle that drives around and explores another world.
- Iron oxide
- Rust! Iron joined with oxygen. It makes Mars red.
- Sol
- One day on Mars, about 24 hours and 40 minutes.
- Solar panel
- A flat panel that turns sunlight into electricity.
Quick quiz!
0 / 31. Why is Mars red?
2. Why can’t anyone steer a Mars rover live with a joystick?
3. What colour is the daytime sky on Mars?
Questions kids ask
Why is Mars called the red planet?
Its surface is covered in rusty dust made of iron oxide, which gives it a red colour.
Can people live on Mars?
Not yet. The air is too thin to breathe and it is very cold. Scientists are studying how astronauts might one day visit.
How long does it take to get to Mars?
Spacecraft usually take about seven months to travel from Earth to Mars. See how rockets work in how do rockets work.
How many rovers are on Mars?
Several rovers have landed on Mars since 1997, sent by NASA and China. Some still work today, while others have ended their missions and stay where they stopped.
Rover Mission
Rovers have no steering wheel. Line up your commands, press transmit and guide the rover around craters to find the iron-rich red rock.
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