Astonishing discovery of minerals on Mars hints at a habitable past

Even though Mars is now a cold and dry world, it once hosted rivers, lakes, and possibly vast oceans. Robotic missions search for traces of this past. Some discoveries take years, while others, like unexpected mineral clues, appear suddenly.

A rover traversing the Martian surface may seem routine, but when that rover is NASA’s Perseverance and it encounters something extraordinary, the discovery sends ripples through the scientific community.

Roger Wiens, professor of earth, atmospheric, and planetary sciences at Purdue University, witnessed one of these moments when Perseverance’s laser struck some pale rocks that turned out to be anything but ordinary.

A chance encounter with intriguing clues

The rocks in question looked different from the rest. They were paler, and stood out against the usual Martian landscape.

That alone made them interesting, but what truly surprised Wiens and his team was their composition. These rocks contained an unusually high amount of aluminum, linked with the mineral kaolinite.

This, in itself, would have been a noteworthy discovery. But kaolinite is no ordinary mineral. On Earth, it forms only under very specific conditions – ones that involve warmth, moisture, and long-term exposure to water.

Finding it on Mars meant that, at some point in its history, the planet must have been wetter, and possibly even significantly warmer than previously believed.

“On Earth, these minerals form where there is intense rainfall and a warm climate or in hydrothermal systems such as hot springs. Both environments are ideal conditions for life as we know it,” Wiens said.

If the conditions that created these minerals were present on Mars for an extended period, it raises questions about whether the planet once supported environments suitable for life. The discovery challenges long-standing ideas about Mars’s climate history.

Mars rover detects minerals

Wiens’s involvement in Mars exploration runs deep. He has spent decades working with rovers and played a crucial role in designing SuperCam, the powerful instrument mounted atop Perseverance. Resembling a head and neck, this device allows the rover to analyze the Martian surface from a distance.

This work is the result of a collaboration involving scientists from Los Alamos National Laboratory and the French Institut de Recherche en Astrophysique et Planétologie, supported by NASA and the Centre National d’Études Spatiales in France.

SuperCam’s tools allow scientists to examine the composition of Martian rocks without requiring the rover to physically touch them. On the first day Perseverance landed, its cameras spotted small, pale pebbles scattered across the landscape. At the time, researchers had other priorities and paid them little attention.

Later, as the rover continued exploring, it came across larger rocks with the same coloration. These rocks were not attached to the underlying bedrock but instead lay loose on the surface.

Known as “float rocks,” they had been moved from their original location, carried by unknown forces across the Martian terrain. That alone made them intriguing. What came next changed everything.

“These rocks are very different from anything we’ve seen on Mars before,” Wiens said. “They’re enigmas.”

Mysterious Mars minerals

Wiens’s research team, including Candice Bedford and Clement Royer, took a closer look at these rocks. The deeper they analyzed, the more astonishing the results became.

More than 4,000 of these pale stones were scattered across the surface, all showing similar characteristics. The presence of kaolinite stood out, but that wasn’t the only surprising element.

Alongside kaolinite, the rocks also contained traces of spinel, most likely aluminum spinel. This mineral typically forms in either igneous or metamorphic environments.

That posed an important question: Did the spinel form first, later interacting with kaolinite, or did the kaolinite somehow develop around the spinel? The answer remains unclear.

On Earth, kaolinite is often found in locations where water has flowed for ages, dissolving away all but the most resilient materials. This means the Martian rocks could be remnants of an ancient, long-lived watery environment.

However, their current hardness differs from Earth’s kaolinite, suggesting additional geological processes have altered them over time.

Mars minerals hold evidence of water

Mars’s history is written in its rocks, and each discovery adds another layer to the story. Water has always been at the heart of that story, raising fundamental questions about how much once existed, how long it lasted, and where it eventually disappeared.

“The big questions about Mars are about water,” Wiens said.

“How much water was there? How long was there water? Given how cold and dry Mars is now, where did all that water go? As a mineral, kaolinite has a lot of water bound up in its structure. It’s possible that a lot of the water is still there, on Mars, bound up in the minerals.”

Even though the research team has not yet found these rocks in their original bedrock location, orbital satellite data confirms that Jezero Crater’s rim contains kaolinite-rich formations. Bedford, who co-led the study, believes that tracking the source of these float rocks could provide answers.

“Although we have not seen these rocks ‘in place’ in bedrock with the rover, and we’re not sure where these float rocks came from, from orbiting satellites we know that there are kaolinite-rich rocks in Jezero crater’s rim,” Bedford said.

“Investigating these rocks in place will help us test our hypotheses on how the rocks formed, how they relate to the ancient Martian environment and the habitability of the planet in the past. We are keeping our eyes wide open, looking for the source of these rocks now that Perseverance is exploring the crater rim.”

Searching for signs of life

Mars’s transformation from a planet with liquid water to the frozen desert we see today remains one of the biggest scientific mysteries.

The discovery of these minerals strengthens the possibility that ancient Mars was not just habitable but sustained environments capable of supporting life.

Since life as we know it depends on water, uncovering the history of water on Mars is key to understanding whether life ever had a foothold there.

The study is published in the journal Nature Communications Earth & Environment.

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