Mars for Kids
Planet 4 from the Sun
Mars is the fourth planet from the Sun. Its day lasts 24.7 hours. Its year lasts 687 Earth days. That is from NASA's planetary fact sheet, checked 29 October 2026. A scale there reads 0.377 times as much as on Earth. Read about it at three levels: Little, Middle and Big, and make your own Space Card.
Mars is a red, dusty planet. Robots called rovers roll around on it. It has two tiny moons.
Mars is red because its dust is full of iron, like rust. A day there is almost the same as ours, 24 hours and 40 minutes, but a year is 687 Earth days. Olympus Mons, the tallest volcano we know, is on Mars.
Mars is cold, about minus 65 degrees Celsius on average, with air so thin that liquid water cannot stay on the surface. Rovers and orbiters have found dry riverbeds that show water once flowed there.
Mars has two moons, Phobos and Deimos, both lumpy like potatoes.
Mars in numbers
| Across | 6,792 km |
|---|---|
| From the Sun | 228 million km |
| A day | 24.7 hours |
| A year | 687 Earth days |
| Pull of gravity | 0.377 times Earth's |
| Average temperature | -65 °C |
| Moons | 2 |
Source: NASA planetary fact sheet, checked 29 October 2026.
How big is Mars?
Mars is 6,792 kilometers across, 53 out of every 100 parts of Earth's width. Mars is 228 million kilometers from the Sun, on average.
How hot or cold is Mars?
Mars averages -65 degrees Celsius, far colder than any freezer on Earth.
Does Mars have moons?
Mars has 2 moons by NASA's count, and the number can grow as telescopes find more.
Can I see Mars tonight?
Not in the evening, but yes before sunrise: south-east, 6 fists above the ground. Sky Tonight gives your own times from a ZIP.
How much would I weigh on Mars?
A child who weighs 80 pounds on Earth would read 30 pounds on Mars. That is a game number: it only shows how hard Mars pulls compared with Earth. Make your own Space Card to guess first and see all eleven worlds.