Mars may have once been home to sun-soaked, sandy beaches, suggests a new study.
The findings “strengthen” the case that the red planet was once home to alien lifeforms, say scientists.
An international research team used data from a Chinese rover that landed on Mars in 2021 to identify hidden layers of rock under the surface that strongly indicate the presence of an ancient northern ocean.
The now-inactive rover, called Zhurong, operated between May 2021 and May 2022.
It traveled 1.2 miles (1.9 kms) near escarpments thought to be an ancient shoreline four billion years ago when Mars had a thicker atmosphere and a warmer climate.
The rover used ground-penetrating radar (GPR) to probe up to 260 feet (80 meters) beneath the surface.
The radar images showed thick layers of material along the entire path, all pointing upward toward the shoreline at about a 15-degree angle, nearly identical to the angle of beach deposits on Earth.
Study co-author Dr. Benjamin Cardenas, Assistant Professor of geology at Penn State University in the US, says the new research offers the clearest evidence yet that the red planet once contained a significant body of water and a more habitable environment for life.
Deposits of the same thickness on Earth would have taken millions of years to form, which scientists say suggest that Mars had a “long-lived” body of water with wave action to distribute the sediments along a sloping shoreline.
The radar was also able to determine the size of the particles in the layers, which matched that of sand.
However, the deposits don’t resemble ancient, wind-blown dunes, which are common on Mars.
Dr. Cardenas said: “We’re finding places on Mars that used to look like ancient beaches and ancient river deltas.
“We found evidence for wind, waves, no shortage of sand – a proper, vacation-style beach.”
The Zhurong rover landed on Mars in 2021 in an area known as Utopia Planitia and sent back data on the geology of its surroundings in search of signs of ancient water or ice.
By studying the underground sedimentary deposits, Dr. Cardenas explained that scientists are able to piece together a more complete picture of the red planet’s history.
When the team reviewed radar data, it revealed a similar layered structure to beaches on Earth: formations called “foreshore deposits” that slope downwards towards oceans and form when sediments are carried by tides and waves into a large body of water.
Dr. Cardenas said: “This stood out to us immediately because it suggests there were waves, which means there was a dynamic interface of air and water.
“When we look back at where the earliest life on Earth developed, it was in the interaction between oceans and land, so this is painting a picture of ancient habitable environments, capable of harboring conditions friendly toward microbial life.”
He explained that when the team compared the Martian data with radar images of coastal deposits on Earth, they found “striking” similarities.
The dip angles observed on Mars fell right within the range of those seen in coastal sedimentary deposits on Earth.
The researchers also ruled out other possible origins for the dipping reflectors, such as ancient river flows, wind or volcanic activity.
The team suggested that the consistent “dipping” shape of the formations as well as the thickness of the sediments point to a coastal origin.
Dr. Cardenas said: “We’re seeing that the shoreline of this body of water evolved over time.”
He added: “We tend to think about Mars as just a static snapshot of a planet, but it was evolving.
“Rivers were flowing, sediment was moving, and land was being built and eroded.
“This type of sedimentary geology can tell us what the landscape looked like, how they evolved, and, importantly, help us identify where we would want to look for past life.”
Professor Hai Liu, of Guangzhou University and a core member of the science team for the Tianwen-1 mission, said: “This strengthens the case for past habitability in this region on Mars.”
The study, published in the journal Proceedings of the National Academy of Sciences (PNAS), also provided new information on the evolution of the Martian environment, suggesting that a “life-friendly” warm and wet period spanned potentially tens of millions of years.
Study corresponding author Professor Michael Manga, of the University of California, Berkeley, said: “The capabilities of the Zhurong rover have allowed us to understand the geologic history of the planet in an entirely new way.
“Its ground-penetrating radar gives us a view of the subsurface of the planet, which allows us to do geology that we could have never done before.”
He added: “All these incredible advancements in technology have made it possible to do basic science that is revealing a trove of new information about Mars.”
