Image: Mars in true color, as captured by the Hope orbiter. The Tharsis Montes can be seen at the center, with Olympus Mons just to the left and Valles Marineris at the right. by – Mars – August 30 2021 (Wikipedia)
By Staff Writer with Agencies
May 4, 2025
Mars — The enduring mystery of why the Red Planet is, in fact, red may have finally found a new explanation. In a breakthrough study published in Nature Communications, researchers now suggest that the rusty hue of Mars is likely due to a water-bearing mineral called ferrihydrite, not the dry hematite once believed responsible, a finding that could rewrite what we know about the planet’s past climate and habitability.
The familiar red dust that coats Mars has long been assumed to result from iron oxidizing through dry processes, forming hematite over billions of years. However, new analysis combining observational data and lab simulations points to ferrihydrite — a poorly crystalline, iron-rich mineral that forms rapidly in cold, watery environments — as the real culprit.
“This discovery changes our fundamental understanding of how Mars got its iconic color,” said Dr. Adomas Valantinas, the study’s lead author and planetary scientist at Brown University. “Mars is still the Red Planet, but the reason it’s red tells a different story about its ancient climate, one where water played a much greater role than we realized.”
Quick Fact: Mars appears red because it's surface is covered with Iron Oxide. pic.twitter.com/qKkbiE4UPL
— Learn to Skywatch (@Learntoskywatch) May 15, 2016
A Watery Past
Mars, named for the Roman god of war due to its blood-like appearance, has captivated human imagination for millennia. For decades, scientists have debated whether its surface conditions were ever suitable for life. This new study adds significant weight to the theory that liquid water once flowed abundantly on the Martian surface.
Ferrihydrite, unlike hematite, requires water and oxygen to form. The team behind the research used data from multiple missions, including ESA’s Mars Express, the ExoMars Trace Gas Orbiter, and NASA’s Curiosity, Pathfinder, and Opportunity rovers. They also recreated Martian dust in laboratory conditions on Earth, matching its size and composition for detailed analysis.
Using high-resolution imaging from the CaSSIS camera onboard the Trace Gas Orbiter, researchers identified dust particles consistent with ferrihydrite mixed with basalt, a volcanic rock common on Mars. These observations, combined with spectral data, revealed signatures of hydrated minerals across even the dustiest regions of the planet.
“The presence of ferrihydrite suggests Mars rusted earlier and in wetter conditions than we believed,” Valantinas said. “This mineral forms in cold water, so its presence hints at widespread liquid water existing around 3 billion years ago, even as Mars was transitioning into a drier, colder planet.”
A Step Closer to Understanding Life Potential
If Mars’ surface was indeed shaped by water-rich environments for longer than previously assumed, that significantly raises the chances the planet once harbored life, or still could beneath the surface.
“The implications are profound,” said Dr. Colin Wilson, ESA scientist for the Mars Express and Trace Gas Orbiter missions. “Ferrihydrite is commonly found on Earth in areas of seasonal melt or sudden downpours, exactly the kinds of hydrological bursts that could have supported microbial life on ancient Mars.”
One of the most important aspects of the study is that it connects laboratory-simulated dust with orbital and rover data. That methodological bridge opens up more reliable interpretations of mineral composition from afar, crucial as missions continue.
Next Steps: Bringing Mars to Earth
Still, the ultimate test of the ferrihydrite theory will come when samples from the Martian surface are returned to Earth. NASA and ESA’s Mars Sample Return campaign, expected to launch later this decade, aims to retrieve rock and dust specimens collected by the Perseverance rover.
“With direct samples, we’ll be able to measure the exact amount and structure of ferrihydrite, verify its formation conditions, and gain unprecedented insight into Mars’ hydrological and atmospheric history,” said Wilson.
In the meantime, questions remain. Where exactly did this mineral originate? How widespread was the water that created it? And what does it tell us about early planetary atmospheres?
Dr. Briony Horgan, a planetary scientist at Purdue University, notes: “Understanding the origin of this dust helps us backtrack through Martian history and determine what kind of world Mars used to be, and if it might resemble Earth more than we imagined.”
With each new revelation, Mars continues to unravel its secrets, one dusty grain at a time.
Staff Writers at Open Chronicle produce in-depth, field-informed reporting on defense, diplomacy, cultural transformation, and global affairs. Known for clarity, accuracy, and analytical depth, they connect breaking developments to broader historical and strategic contexts. In addition to frontline journalism, Staff Writers also contribute to the Open Chronicle Encyclopedia, crafting authoritative entries that preserve critical knowledge and enrich public understanding.