Mars Rover Finds Ancient River Evidence Buried Deep Underground

NASA's Perseverance rover has uncovered underground remnants of an ancient river delta on Mars, dating back over 3.7 billion years. The discovery provides some of the oldest proof that water once flowed on the Red Planet's surface.

NASA’s Perseverance rover has made a groundbreaking discovery on Mars, uncovering buried remnants of an ancient river delta that provides some of the most compelling evidence to date of water flowing on the Red Planet billions of years ago.

The six-wheeled robotic explorer used sophisticated ground-penetrating radar technology to peer beneath the Martian surface, revealing geological structures buried as deep as 115 feet below ground. These findings came as Perseverance traveled across 3.8 miles of terrain within Jezero Crater, located in Mars’ northern hemisphere and believed to have once contained an ancient lake.

Scientists discovered layered sedimentary deposits and weathered surfaces that point to an ancient delta formation – a fan-shaped accumulation of sediment that forms where rivers meet larger water bodies such as lakes. The research team determined this buried delta formation existed approximately 3.7 to 4.2 billion years ago, making it relatively early in Martian history since the planet formed around 4.5 billion years ago, similar to Earth.

This newly discovered delta actually predates another surface formation in the area known as the Western Delta, which scientists estimate to be about 3.5 to 3.7 billion years old.

The breakthrough came through Perseverance’s RIMFAX instrument, which transmits radar signals downward and captures the echoes that bounce back from underground structures, creating detailed three-dimensional maps of what lies beneath the surface. The latest findings represent the deepest subsurface data RIMFAX has collected, gathered between September 2023 and February 2024 across 250 Martian days.

The discovery holds particular significance because scientists consider water essential for the potential existence of past life on Mars. The Red Planet, now a cold and barren world, once had a denser atmosphere and warmer temperatures that would have supported liquid water on its surface.

“From the features mapped by RIMFAX, we believe that Jezero Crater hosted an ancient water-rich environment, capable of biosignature preservation that existed prior to the formation of Jezero’s Western Delta,” explained Emily Cardarelli, a UCLA planetary scientist who serves on the Perseverance science team and authored the study published Wednesday in Science Advances.

Biosignatures represent chemical or physical traces that indicate past or present life forms.

River deltas on Earth serve as natural collection points for sediments and provide environments where microscopic life can thrive.

Last year, researchers announced that a rock sample collected by Perseverance in Jezero Crater contained what might be a biosignature suggesting ancient microbial life, though the minerals found could also result from non-biological processes. That rock sample dated to roughly 3.2 to 3.8 billion years ago.

Perseverance has been investigating Jezero Crater since arriving in 2021. Researchers believe ancient river channels once flowed over the crater’s rim, filling it with water to create a lake.

“It’s very exciting that RIMFAX was able to provide such a detailed view of these deposits, and thus help solve the puzzle of their origin,” said David Paige, a UCLA planetary scientist and study co-author who also works with the Perseverance science team. “This further cements the notion that ground-penetrating radar is indeed an extremely valuable new tool for studying planetary geology.”

Chinese researchers made similar discoveries last year when their Zhurong rover used ground-penetrating radar to find subsurface evidence resembling sandy shorelines from what may have been an ocean in Mars’ northern plains.

“Over time, we’ve seen more and more evidence for liquid water on the Martian surface at various rover landing sites, areas we’ve traversed to, as well as from orbital imagery. We have seen channels where water may have flowed, crater lakes where water once ponded, and deltaic sediments deposited as rock outcrops and now as buried remnants, with this (research) paper,” Cardarelli noted.

“Mars is diverse, and each rover mission reveals another piece of its puzzling past and the early development of our rocky neighbor,” she added.