Hidden layers of rock below the surface of Mars "strongly suggest" the presence of an ancient ocean, according to an international team of scientists including researchers at Penn State.
From the university's announcement:
The new research offers the clearest evidence yet that the planet once contained a significant body of water and a more habitable environment for life, according to Benjamin Cardenas, assistant professor of geology at Penn State and co-author on the study. "We're finding places on Mars that used to look like ancient beaches and ancient river deltas," Cardenas said. "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. Unlike other rovers, it came equipped with rover-penetrating radar, which allowed it to explore the planet's subsurface, using both low and high-frequency radar to penetrate the Martian soil and identify buried rock formations. By studying the underground sedimentary deposits, scientists are able to piece together a more complete picture of the red planet's history, Cardenas explained. 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.
"This stood out to us immediately because it suggests there were waves, which means there was a dynamic interface of air and water," Cardenas said. "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." When the team compared the Martian data with radar images of coastal deposits on Earth, they found striking similarities, Cardenas said. The dip angles observed on Mars fell right within the range of those seen in coastal sedimentary deposits on Earth...
The study 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.
Mars "was evolving," Cardenas says in the announcement. "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."
CNN notes that the research was published Monday in the journal Proceedings of the National Academy of Sciences.
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