Curiosity rover finds coral-like rocks on Mars, revealing billions of years of water activity

On July 24, NASA's Curiosity rover transmitted images of a rock no larger than an inch across, its surface sculpted into something that resembled a piece of coral reef. The rover, which has been roaming Mars since 2012, had encountered many such formations before, but each one told the same story: billions of years ago, this planet was wet.

The mechanism behind these shapes is straightforward, though the results are striking. When Mars still held liquid water—a time so distant that the planet has since become a frozen desert—that water carried dissolved minerals as it moved through the cracks and fissures in rock. As the water evaporated, it left behind hardened mineral deposits. The same process occurs on Earth regularly, producing intricate formations in caves and along riverbeds. On Mars, it created something more alien: rocks that looked like flowers, like coral, like the skeletal remains of life itself.

One specimen discovered on the same day was given the nickname "Paposo." Another flower-shaped rock had turned up three years earlier, in February 2022. What made these discoveries significant was not their beauty, though they possessed that in abundance. Rather, they were evidence. Each formation represented a chapter in Mars's transformation from a world of flowing water to the barren landscape we see today. The Jet Propulsion Laboratory, which built and operates Curiosity, had sent the rover to Gale Crater—an ancient impact basin—specifically to read those chapters.

The rover itself is a testament to human ambition. After traveling 352 million miles over eight months, it touched down on Mars in 2012 as the largest and most capable rover ever dispatched to the planet. Since then, it has covered roughly 22 miles of Martian terrain, collecting samples and data from an era when the planet may have harbored microbial life. The coral and flower rocks were just the latest puzzle pieces.

In June, Curiosity had photographed another geological feature called "spiderwebs"—a pattern of ridges that suggested water had been present even as Mars was drying out. The wind had spent eons scouring the rock, wearing away the softer material but leaving behind the resistant mineral networks, like a relief map of ancient hydrology. These discoveries raised urgent questions about the mechanics of planetary change. Mars once possessed rivers and lakes, possibly even an ocean. Yet something—scientists remain uncertain what—caused that water to vanish. The planet became the cold, dry world we know now. But the evidence in the rocks suggested that even during this transition, water persisted underground, still carving and reshaping the surface in ways we are only now beginning to read.

As Curiosity continues to gather data from the Gale Crater and beyond, each image and measurement adds texture to a portrait of a world in flux. The coral-like rocks are not merely curiosities. They are records of a planetary biography, written in mineral and stone, waiting to be deciphered.