Mars
Stop 7 of 12 · Inner Solar System
Mars
The red planet — a cold, dusty world of giant volcanoes, deep canyons, and ancient rivers.
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Explore Mars — why it is red, what giant landmarks it holds, and what its dusty surface may be hiding.
Some nights, Leela notices a light in the sky that is not white like the stars — it glows softly reddish-orange. She has seen pictures of it in books: a world the color of dried clay, with polar caps of white.
"Mars," she says to Manjari. "The red planet. But why is it red?"
Why is Mars red? Is the ground actually painted that color?
Think about an old iron nail left out in the rain. It turns orange-brown and flaky. What is happening to the metal? Now imagine that happening across a whole planet…
Mars looks red because its soil is full of iron oxide — the same rusty compound that forms on old iron left out in the rain. Martian dust has been rusting for billions of years, and winds blow that reddish dust across the whole planet.
A Land of Giants
Mars is a small, cold desert world, but it holds the most dramatic scenery in the Solar System:
- Olympus Mons — the tallest volcano known, roughly three times the height of Mount Everest
- Valles Marineris — a canyon system so long it would stretch across the entire United States
- Polar ice caps — white caps of water ice and frozen carbon dioxide that grow and shrink with the seasons
Mars is far colder than Earth — its average temperature is around -60 °C. And its air is thin, mostly carbon dioxide. You could not breathe there without a spacesuit.
- Order from Sun
- Fourth of the eight planets
- Approximate diameter
- 6,779 km
- Known moons
- 2
- Year length
- 687 Earth days
Mars has two tiny moons, Phobos and Deimos — named after the Greek words for fear and dread, the companions of the god of war.
The Search for Water
Mars is dry now, but it was not always. Spacecraft have found dried-up riverbeds, lakebeds, and minerals that only form in water. Long ago, Mars may have had rivers, lakes, and maybe even oceans.
That is why scientists are so curious — where there was water, there may once have been life. Today, rovers roll across its surface, drilling into the dust and sending home messages from another world.
Mars has seasons just like Earth! Because its axis is tilted, Mars experiences spring, summer, autumn, and winter — though each season lasts about twice as long as ours.
Why Does This Matter?
Studying Mars helps scientists understand how planets change over time — and whether environments beyond Earth might once have supported life. Every rover wheel-track is a step toward answering one of the oldest questions: are we alone?
If you could send one question to a rover on Mars, what would you ask it?
Quick Check
Why does Mars appear red?
Mars is a cold, dusty world colored red by rust. It holds the Solar System's tallest volcano and deepest canyon — and evidence that liquid water once flowed across its surface.
Reflect
What You Discovered
- Mars is red because of iron oxide — rust
- It holds the Solar System's tallest volcano and deepest canyon
- Ancient riverbeds suggest water once flowed
- A Martian year lasts about twice as long as ours