How do we know?
↻ One of the pages with a moving picture
A rover drilled a hole in Mars, and the powder that came out was gray.
- The ground on Mars has iron in it.
- Much of that iron has turned to rust. NASA calls it “rusty iron in the ground.”
- Wind blows the reddish dust all over, sometimes in giant dust storms and swirling dust devils.
- A coat of this rusty dust makes the whole planet look red.
In 2013, NASA’s Curiosity rover pressed its drill into a flat Martian rock and bored a hole about as wide as a pencil. Everyone expected red powder. What came up was gray.
That is the clue. The red is a thin coat of rusty dust lying on the outside. Underneath, Mars is gray rock — like a bicycle left out in the rain, orange on the outside and still shiny steel if you scratch it.
We can also hold pieces of Mars in our hands. Asteroid strikes have blasted rocks off the planet, and some drifted through space and landed here as meteorites. Scientists have been testing those rocks for over a hundred years.
Wow number
16 miles (25 km): about how tall Olympus Mons, a giant volcano on Mars, stands from bottom to top.
Myth or fact?
Mars is red because it is very hot. Myth. Mars is a cold place — about -85 °F (-65 °C) on average. The colour comes from rust, not from heat.
A day on Mars is a little longer than a day on Earth. Fact. It lasts about 24.6 hours, so a Martian morning slides a bit later every day.
Think about it
One rock from Mars was found lying on the ice in Antarctica. Others fell out of the sky over Egypt. How do you think a rock could leave Mars and end up on Earth?
Where in the world?
Allan Hills, Antarctica where a snowmobile ride on 27 December 1984 turned up a rock from Mars. More Mars rocks fell near El-Nakhla, Egypt, on 28 June 1911 — 76.72° S, 159.67° E.
Where these facts come from
Every number on page 14, and who measured it
Mars looks red because of rusty iron in its ground, and it is a cold planet — about -85 °F (-65 °C) on average.
All About Mars — NASA Space Place, NASA's science site for kids
spaceplace.nasa.gov/all-about-mars/en
We checked it on 31 October 2026
A day on Mars lasts about 24.6 hours, and Olympus Mons is the largest volcano in the solar system.
Mars: Facts — NASA, the U.S. space agency
science.nasa.gov/mars/facts
We checked it on 31 October 2026
Olympus Mons stands about 25 km (16 mi) from bottom to top.
Olympus Mons Flank — NASA's Jet Propulsion Laboratory
jpl.nasa.gov/images/pia24852-olympus-mons-flank
We checked it on 31 October 2026
Curiosity drilled its first sample hole into a Martian rock in 2013.
Curiosity's First Sample Drilling — NASA, the U.S. space agency
science.nasa.gov/photojournal/curiositys-first-sample-drilling
We checked it on 31 October 2026
The powder Curiosity's drill brought up from inside the rock was gray, not red — the red is only a surface coating.
Studying Habitability in Ancient Martian Environments — NASA, the U.S. space agency
science.nasa.gov/resource/studying-habitability-in-ancient-martian-environments
We checked it on 31 October 2026
The Martian meteorite ALH 84001 was found in the Allan Hills, Antarctica, on 27 December 1984.
NASA's space-rock curators, who look after meteorites
curator.jsc.nasa.gov/antmet/mmc/alh84001.pdf
We checked it on 31 October 2026
The Nakhla meteorites fell near El-Nakhla, Egypt, on 28 June 1911.
NASA's space-rock curators, who look after meteorites
www-curator.jsc.nasa.gov/antmet/mmc/Nakhla.pdf
We checked it on 31 October 2026
Has this changed?
Mars has been rusty for billions of years, so this answer is not going to change.
What keeps changing is how much of Mars we have looked at closely. Every rover that lands drills a few more holes, and every hole tells us a little more about what is under the red.
Words from this page
- rust
- The orange-red crust that forms when iron meets water and air.
- dust devil
- A small spinning column of wind that picks dust up off the ground.
- meteorite
- A rock from space that has landed on a planet and survived the fall.
Try it!
Make rust, and watch the colour of Mars appear on your kitchen table.
1. With a grown-up, put on gloves and pull apart a pad of plain steel wool. 2. Lay it on a dish and sprinkle it with water. 3. Look at it every day for a few days.
What happens: the gray steel turns orange-red. Iron and water and air together make rust — the very same colour as the dust on Mars.
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