For decades, scientists hypothesized that Mars’ reddish color came from hematite, an iron oxide thought to have formed through dry oxidation after Mars lost its water. But new research suggests the story is more complex—and more watery—than we once imagined.

In this episode, planetary scientist Adomas (Adam) Valantinas from Brown University joins host Sarah Al-Ahmed to discuss his team’s discovery that Mars’ iconic red dust is likely dominated not by hematite but by a hydrated mineral called ferrihydrite. This subtle but significant shift in understanding could reshape what we know about Mars’ climate history and its potential for past habitability. 

Then, Sarah and Bruce Betts, Planetary Society chief scientist, revisit one of the most famous Martian discoveries: Opportunity’s hematite-rich “blueberries,” which also told a compelling story about water on the Red Planet.

Discover more at: https://www.planetary.org/planetary-radio/2025-why-is-mars-red

For decades, scientists hypothesized that Mars&rsquo; reddish color came from hematite, an iron oxide thought to have formed through dry oxidation after Mars lost its water. But new research suggests the story is more complex&mdash;and more watery&mdash;than we once imagined.
In this episode, planetary scientist Adomas (Adam) Valantinas from Brown University joins host Sarah Al-Ahmed to discuss his team&rsquo;s discovery that Mars&rsquo; iconic red dust is likely dominated not by hematite but by a hydrated mineral called ferrihydrite. This subtle but significant shift in understanding could reshape what we know about Mars&rsquo; climate history and its potential for past habitability.&nbsp;
Then, Sarah and Bruce Betts, Planetary Society chief scientist, revisit one of the most famous Martian discoveries: Opportunity&rsquo;s hematite-rich &ldquo;blueberries,&rdquo; which also told a compelling story about water on the Red Planet.
Discover more at:&nbsp;<a href="https://www.planetary.org/planetary-radio/2025-why-is-mars-red">https://www.planetary.org/planetary-radio/2025-why-is-mars-red</a>

Planetary Radio brings you the human adventure across our Solar System and beyond. We visit each week with the scientists, engineers, leaders, advocates, and astronauts who are taking us across the final frontier. Regular features raise your space IQ while they put a smile on your face. Join host Sarah Al-Ahmed and Planetary Society colleagues including Bill Nye the Science Guy and Bruce Betts as they dive deep into space science and exploration. The monthly Space Policy Edition takes you inside the DC beltway where the future of the US space program hangs in the balance. Visit planetary.org/radio for an episode guide and much more.

Planetary Radio brings you the human adventure across our Solar System and beyond. We visit each week with the scientists, engineers, leaders, advocates, and astronauts who are taking us across the final frontier. Regular features raise your space IQ while they put a smile on your face. Join host Sarah Al-Ahmed and Planetary Society colleagues including Bill Nye the Science Guy and Bruce Betts as they dive deep into space science and exploration. The monthly Space Policy Edition takes you inside the DC beltway where the future of the US space program hangs in the balance. Visit planetary.org/radio for an episode guide and much more.

Planetary Radio: Space Exploration, Astronomy and Science

Planetary Radio brings you the human adventure across our solar system and beyond. We visit each week with the scientists, engineers, leaders, advocates, and astronauts taking us across the final frontier. Regular features raise your space IQ while they put a smile on your face. Join host Sarah Al-Ahmed and Planetary Society colleagues including Bill Nye, the Science Guy, and Bruce Betts, chief scientist for The Planetary Society, as they dive deep into the latest space news. The monthly Space Policy Edition takes you inside the DC beltway with Casey Dreier and Jack Kiraly to discuss the politics of space exploration in the US and advocacy actions you can take to support the missions that matter. Visit planetary.org/radio for the space trivia contest, an episode guide, and much more.

Planetary Radio brings you the human adventure across our solar system and beyond. We visit each week with the scientists, engineers, leaders, advocates, and astronauts taking us across the final frontier. Regular features raise your space IQ while they put a smile on your face. Join host Sarah Al-Ahmed and Planetary Society colleagues including Bill Nye, the Science Guy, and Bruce Betts, chief scientist for The Planetary Society, as they dive deep into the latest space news. The monthly Space Policy Edition takes you inside the DC beltway with Casey Dreier and Jack Kiraly to discuss the politics of space exploration in the US and advocacy actions you can take to support the missions that matter. Visit planetary.org/radio for the space trivia contest, an episode guide, and much more.

Why is Mars red? A new study led by Brown University’s Adomas Valantinas points to ferrihydrite, not hematite, revealing a wetter past and new clues about the Red Planet’s potential to support life.

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