What Is Mars? The Red Planet, Explained

Mars is the fourth planet from the Sun and the next one out past Earth — a cold, dry, dusty desert world about half the size of our own. It’s nicknamed the Red Planet because its surface is covered in iron-rich dust that has literally rusted, giving the whole world a reddish-orange color. Mars is the planet humans know best after Earth, the target of dozens of robotic missions, and the place SpaceX hopes to one day settle. Here’s what it’s actually like, in plain English.

Why Mars is red

The color comes down to rust. Martian soil and dust are rich in iron, and over billions of years that iron has reacted with oxygen to form iron oxide — the same compound that makes rust orange on Earth. Fine dust storms spread that material across the whole planet, so Mars looks red even from millions of kilometers away. To the naked eye from Earth, it shows up as a distinctly reddish “star” in the night sky.

Key facts about Mars

A quick tour of what makes Mars, Mars:

• Size — about half Earth’s diameter, with roughly 38% of Earth’s surface gravity. You’d weigh less than half of what you do here.
• A day — almost exactly like ours, at about 24 hours and 39 minutes. A Martian year, though, lasts nearly two Earth years.
• Temperature — cold. The average is around minus 60°C (minus 80°F), though a warm summer afternoon near the equator can briefly climb above freezing.
• Thin air — the atmosphere is about 1% as dense as Earth’s and is mostly carbon dioxide. You could not breathe it, and liquid water can’t stay stable on the surface.
• Two tiny moons — Phobos and Deimos, small lumpy rocks likely captured from the asteroid belt.

A dramatic landscape

For a small, quiet world, Mars has some of the most extreme terrain in the solar system. It’s home to Olympus Mons, a volcano about three times the height of Mount Everest and the tallest known mountain on any planet. It also has Valles Marineris, a canyon system so long it would stretch across the entire United States and so deep it dwarfs the Grand Canyon.

The planet is also covered in features that look carved by water — dried-up riverbeds, ancient lake basins and mineral deposits that only form in wet conditions. The evidence strongly suggests that billions of years ago, Mars was warmer, wetter, and had rivers, lakes and maybe even an ocean.

Is there life on Mars?

No life has ever been found on Mars, and there’s no confirmed evidence that any ever existed. But the question is very much open. Because early Mars appears to have had liquid water and a thicker atmosphere, it may once have been habitable for microbes. Today, robotic rovers are searching for chemical traces — “biosignatures” — that ancient microscopic life might have left behind in the rocks. Frozen water also survives at the poles and underground, which matters both for the search for life and for any future human visitors.

Why people want to go to Mars

Mars is the most realistic target for human settlement beyond Earth. It has a day length close to ours, frozen water that could be turned into drinking water, breathable oxygen and rocket fuel, and a solid surface to land and build on. None of that makes it easy — the thin air, brutal cold, radiation and months-long journey are enormous challenges — but it’s far friendlier than anywhere else nearby.

That’s why SpaceX was founded with the explicit goal of making humanity “multi-planetary,” and why it’s building Starship, a giant fully reusable rocket designed to carry people and cargo to the Red Planet. Whether or not the ambitious timelines hold, Mars is the destination driving much of today’s push into deep space.

How to see Mars from Earth

You don’t need a spacecraft to see Mars — you can spot it with your own eyes.

• Look for a reddish point of light. Unlike twinkling stars, planets shine with a steadier glow, and Mars has an unmistakable orange-red tint.
• Catch it near “opposition.” Roughly every two years, Earth passes between Mars and the Sun, bringing the two planets closest and making Mars especially bright. Our guide to how to see the planets explains when and where to look.
• Use a telescope for detail. Through a small telescope you can make out Mars as a tiny orange disk, and a good one can reveal its bright polar ice caps and dark surface markings. Start with our guide to the best telescopes for beginners.

FAQ

What is Mars in simple terms?

Mars is the fourth planet from the Sun and Earth’s outer neighbor — a cold, dry, rocky desert world about half the size of Earth. It’s called the Red Planet because rusty, iron-rich dust covers its surface and gives it a reddish color.

Why is Mars called the Red Planet?

Its surface is covered in dust rich in iron that has rusted, forming reddish iron oxide. Dust storms spread that material across the whole planet, so Mars appears red even when viewed from Earth with the naked eye.

Is there life on Mars?

No life has ever been found there, and none is confirmed to have existed. But because early Mars had liquid water and a thicker atmosphere, it may once have been habitable, and robotic rovers are actively searching the rocks for signs of ancient microbial life.

Why do people want to go to Mars?

Mars is the most realistic place to settle beyond Earth. It has a day length close to ours, frozen water that could supply drinking water and rocket fuel, and a solid surface to build on. SpaceX is developing Starship specifically to carry people there.

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Spaceflight programs and our knowledge of other worlds change over time. This explainer reflects the current landscape and is reviewed periodically.