Why is Mars red? It's not the heat
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Mars looks red, but it isn't hot: it's a cold desert world. The red is rust, because iron in its rocks and dust has oxidized, and winds spread that dust all over the planet. A 2025 study suggests the main red mineral is ferrihydrite, which forms in cool water, so Mars may have rusted long ago while it still had water. Scientists hope to confirm this when samples from Mars come back to Earth.
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Transcript
- Sef Mars is red because it's super hot, right?
- Tiggy Not even close. Mars is cold. That red is rust.
- Tiggy Iron in its rocks and dust has rusted.
- Tiggy Wind spreads that dust all over the planet.
- Sef Rust? But Mars is so dry!
- Tiggy Today, yes. But a recent study suggests the main red mineral forms in cool water.
- Tiggy So Mars may have rusted long ago, while it still had water.
Sources
- NASA: Mars Facts science.nasa.gov
- ESA: Have we been wrong about why Mars is red? esa.int
- Brown University: Why is Mars red? Scientists may finally have the answer brown.edu
- Valantinas et al. 2025, Nature Communications 16:1712 doi.org
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