Why Mars Is Red Has Always Been a Mystery. Now, NASA Knows Why.

If you're one of the many people who have wondered exactly why the planet Mars has a red color — so red, in fact, that it's known as the Red Planet — you're in for some interesting revelations.

A study, funded in part by NASA, sheds some new light on why Mars is red — and why the reasons behind the color actually indicate that Mars may have been fit for life in the past. Keep reading to learn more.

A study published in the journal Nature Communications on Feb. 25, 2025 found that ferrihydrite, which is a "hydrated iron oxide-bearing mineral," is the key mineral that makes up Mars' red dust.

Previously, research has found that the combination of various iron oxides and minerals on Mars were responsible for the red hue, according to NASA. Specifically, as the study notes, anhydrous minerals (compounds that contain no water) were regarded as the reason.

But the February 2025 research — which utilized data from various missions to Mars — indicates that specifically, the iron oxide ferrihydrite is responsible. And ferrihydrite is hydrated, meaning it contains water.

"The fundamental question of why Mars is red has been considered for hundreds if not for thousands of years," lead author Adam Valantinas stated, per NASA.

"From our analysis, we believe ferrihydrite is everywhere in the dust and also probably in the rock formations," he continued. "As Martian winds spread this dust everywhere, it created the planet’s iconic red appearance."

The researchers behind this study are excited about the connection between ferrihydrite and Mars' red hue; however, they may be more excited about the greater meaning of this mineral's presence on Mars.

As explained in the study, because ferrihydrite is a hydrated mineral, it's probable that it formed "during cold water activity in the last stages of early Mars."

The fact that ferrihydrite is so omnipresent on Mars (as we now know, thanks to this study) implies that Mars once had water before evolving into the dry, arid environment the planet is known for today.

“These new findings point to a potentially habitable past for Mars," co-author Geronimo Villanueva stated, per NASA.

However, the study's authors believe that more research must be done to understand the water activity and livability on Mars — and both the Perseverance rover and proposed Mars Sample Return mission will help with that.

"What we want to understand is the ancient Martian climate, the chemical processes on Mars — not only ancient — but also present," stated Valantinas, per NASA. "Was there ever life?"

Hopefully, current and future missions to Mars will soon give us further insight into the exciting question of whether there ever was — or, more interestingly, ever could be — life on Mars.