Mars has fascinated people for centuries, not only because it is our closest neighbor in space but also because of its striking red color.
The Red Planet’s rusty hue has been a mystery for a long time, but now, scientists believe they have finally figured out why Mars is red—and the answer may reveal more about its past.
A new study published in Nature Communications suggests that a mineral called ferrihydrite is responsible for Mars’ reddish dust.
This research, led by scientists from Brown University and the University of Bern, challenges the long-standing idea that another mineral, hematite, is the main cause of the planet’s color.
Ferrihydrite is an iron-rich mineral that forms in wet environments. On Earth, it is often found where volcanic rocks are exposed to water.
The discovery of ferrihydrite on Mars suggests that the planet was once much wetter than it is today.
Since liquid water is essential for life, this finding raises new questions about whether Mars could have once supported life.
“The question of why Mars is red has been around for hundreds, even thousands, of years,” says Adomas Valantinas, a scientist at Brown University.
“We believe ferrihydrite is found all over the dust and rock formations on Mars. Others have suggested this idea before, but we are the first to prove it using real data and lab experiments.”
To reach this conclusion, the researchers used information from several Mars missions, including NASA’s Mars Reconnaissance Orbiter and rovers like Curiosity, Pathfinder, and Opportunity. These spacecraft collected detailed data about the minerals on Mars’ surface. The team then recreated Martian dust in a lab to study how light reflects off ferrihydrite and compared it to actual Mars observations.
They found that ferrihydrite particles in their experiments closely matched the appearance of Mars’ surface. The tiny dust particles—about 1/100th the width of a human hair—are spread across the planet by Martian winds, creating its signature red color.
The discovery is exciting because it supports the idea that Mars had a cooler, wetter past. Unlike hematite, which forms in dry conditions, ferrihydrite forms in the presence of water and oxygen. This suggests that billions of years ago, Mars had water and a very different climate from today’s cold, dry world.
While this research provides strong evidence, scientists say the final proof will come when rock and dust samples from Mars are returned to Earth. NASA’s Perseverance rover is currently collecting these samples, and once they arrive, scientists will be able to confirm their findings.
“This study is a big step forward,” says planetary scientist Jack Mustard. “But the real test will be when we can analyze actual Mars samples here on Earth.”
For now, the mystery of why Mars is red may finally be solved, and with it, a new chapter in our understanding of the Red Planet’s past.
