An artist's illustration of Mars. (Image courtesy of SCIEPRO/SCIENCE PHOTO LIBRARY via Getty Images)
A new study suggests our understanding of the origin of Mars' red color may be wrong.
The Red Planet owes its distinctive hue to rusty iron minerals that have been blown across the Martian dust by winds for millions of years. Previous observations of Martian dust by spacecraft have led scientists to speculate that the rust formed in dry conditions after the planet's water disappeared.
But a new study published Feb. 25 in the journal Nature Communications challenges that view. Instead, the authors suggest that Mars’s red hue is better suited to ferrihydrite, an iron oxide that contains water, indicating that the color may have formed when the current, waterless planet was a cool ocean world. In other words, Mars may be red today because it was blue in the past.
“Our results open up new questions about Mars’s past,” study lead author Adomas Valantinas, a planetary scientist at Brown University, told Live Science. “We still don’t know exactly where the source of the ferrihydrite was before it was spread across the planet via dust storms, what the exact chemical composition of Mars’ atmosphere was when the ferrihydrite formed, or exactly when Mars began to oxidize.”
Mars' vibrant color has captured the attention of astronomers for centuries. The Romans named the planet after the god of war because of its bloody color, and the ancient Egyptians called it “her desher,” meaning “red,” according to NASA.
In the modern era, spacecraft exploring the Red Planet have not detected water in the Martian dust. Therefore, scientists attributed the planet's red color to an iron oxide called hematite, which forms in dry conditions. However, the lack of detailed laboratory experiments left this conclusion in question.
To delve deeper into the origins of Mars' color, researchers working on the new project collected data from three orbiters orbiting Mars – the European Space Agency's (ESA) Mars Express and Trace Gas Orbiter (TGO), as well as NASA's Mars Reconnaissance Orbiter – as well as NASA's Curiosity, Pathfinder, and Opportunity rovers, to create an unprecedented view of the planet's mineral composition and dust particle size.
With this information, the scientists used an advanced grinding machine to create a realistic model of Martian dust with a grain size about one-hundredth the width of a human hair in a laboratory on Earth. Analyzing this dust using the same methods as the spacecraft, the researchers found that the Martian dust closely resembled the signatures of ferrihydrite, which formed in cold, wet climates.
While this result answers one important question, the findings also raise new ones, such as what they can tell us about potential habitability windows on the planet and the possibility of life existing on its surface.
“Ferrihydrite forms in the presence of liquid water and forms rapidly in cold, wet, oxidizing conditions, typically at near-neutral pH. In contrast, hematite can form in warm, dry conditions through slow chemical weathering processes,” Valantinas said. “This discovery implies that Mars experienced hydrous phases — cold, wet conditions with active chemistry — before becoming the desert it is today. It refines the timeframe for Mars’ habitability and points to potential environments where microbial life could have evolved.”
“We look forward to the results of future missions, such as ESA’s Rosalind Franklin rover and the NASA-ESA sample return, which will give us further insight into what
Sourse: www.livescience.com
