Scientists exploring Mars have uncovered strong new evidence that the Red Planet once had wave-washed beaches and long-lasting water activity, making it an even more promising place to search for ancient life.
The discovery comes from NASA’s Perseverance rover, which has been studying rocks inside Jezero crater—an area known to have held a large lake around 3.5 billion years ago.
In a new international study led by researchers at Imperial College London, scientists found that a rocky region called the “Margin unit,” located along the inner edge of Jezero crater, records a surprisingly complex history of water.
The rocks show clear signs of both underground water circulation and surface waves shaping a shoreline. Together, these findings suggest that habitable conditions at Jezero lasted longer than scientists previously believed.
On Earth, shorelines are rich environments for life. They also tend to preserve chemical and physical clues about past conditions.
This makes the discovery of an ancient Martian beach especially exciting. The rocks in Jezero contain carbonate minerals, which form in water and are known on Earth for their ability to trap and preserve organic material.
Perseverance spent nearly a year closely examining the Margin unit between 2023 and 2024.
Before the rover arrived, scientists debated how these rocks formed. Some thought they were sediments laid down at the edge of the ancient lake, while others believed they were volcanic rocks later changed by water.
By analyzing thousands of detailed images taken by the rover, the research team found that both ideas were partly correct.
Much of the Margin unit appears to have started as igneous rock, formed from magma or lava within the crater. After the rock cooled, water rich in carbon dioxide moved through it underground.
This water chemically altered minerals such as olivine, turning them into carbonate minerals over long periods of time. On Earth, similar underground environments can provide energy and nutrients for microbial life, even without sunlight.
The most striking discovery, however, was found at lower elevations of the Margin unit. There, the rover spotted layered sandstone made of small, rounded grains.
These grains show patterns that, on Earth, are classic signs of waves moving back and forth in shallow water. In other words, scientists are confident they are looking at the remains of an ancient beach.
This beach formed when waves from the Jezero lake eroded nearby rocks, rounded the grains, and deposited them along the shoreline.
Importantly, this sandy beach lies beneath the large river delta that Perseverance explored earlier in the mission. That means calm, stable lake conditions existed before the delta formed, pushing the start of habitable conditions further back in time.
The findings build on earlier research by the same team, which identified signs of a younger lake elsewhere in the region. In a dried-up river valley that once fed Jezero crater, scientists found thick layers of mudstone. These rocks suggest that the valley itself was once underwater, likely because a natural blockage created a dammed lake upstream.
Several rock samples collected by Perseverance from both the Margin unit and this upstream area are now waiting to be brought back to Earth by a future Mars Sample Return mission.
Once in laboratories, scientists will be able to date the rocks precisely, study Mars’s ancient climate in detail, and search for possible chemical signs of past life.
Together, these discoveries show that water shaped Jezero crater in many different ways over long periods. Mars, it seems, was not just briefly wet—but may have hosted stable, life-friendly environments long enough for something remarkable to happen.
