NASA’s Perseverance Rover Discovers Hidden River Delta Beneath Mars Surface
Hidden beneath the surface of Mars’ Jezero Crater lies evidence of an even older river system than previously known, according to data recently analyzed by NASA’s Perseverance rover. The discovery, based on radar scans collected between September 2023 and February 2024, suggests Mars may have been habitable for a longer period than scientists initially believed.
The findings center on a region called Margin Unit, located between the western delta and the crater’s edge. Perseverance’s RIMFAX (Radar Imager for Mars’ Subsurface Experiment) instrument, which sends radar pulses into the ground, revealed layered geological structures extending more than 35 meters below the surface, potentially reaching a total thickness of 85 to 90 meters. These layers exhibit patterns consistent with clinoforms – sedimentary deposits formed by flowing water entering a lake.
“It extends the window of fluvial deposition on Mars,” said Emily Cardarelli, a scientist at the University of California, Los Angeles, and lead author of the study published in Science Advances. On Earth, similar mineral formations often preserve evidence of past life, including microbial fossils.
Perseverance initially landed in Jezero Crater in February 2021, tasked with searching for signs of ancient microbial life and collecting samples for potential return to Earth. Early explorations focused on the well-defined Western Delta, a fan-shaped geological formation believed to have formed billions of years ago from a river flowing into a lake. However, the newly discovered subsurface delta predates the visible surface features.
Since landing, Perseverance has steadily revealed a history of water on Mars. In 2022, the rover discovered organic material within sedimentary rocks at the base of the delta, indicating that rivers once carried material from a wide area into the ancient lake. In 2023, observations in the Skrinkle Haven area revealed large rocks and gravel arranged in curved patterns, suggesting the presence of powerful river currents. The rover also identified evidence of periodic, large-scale flooding in the Margin Unit, indicating a fluctuating climate.
More recently, in early 2026, Perseverance reached the crater rim, finding carbonate deposits typically formed in aquatic environments like shorelines. These deposits suggest prolonged interaction between water and the Martian atmosphere, potentially creating conditions suitable for preserving microbial life.
While the subsurface structures strongly resemble a river delta, scientists caution that other geological processes could explain the radar data. Volcanic activity, ancient shorelines, or glacial activity are all potential alternative explanations. However, Cardarelli noted that the complexity and scale of the observed structures are more consistent with fluvial processes.
The current analysis is based on approximately 6.1 kilometers of Perseverance’s total travel distance, which exceeds 39.43 kilometers as of December 5, 2025. A significant amount of data collected along the rover’s 40-kilometer path remains to be analyzed, suggesting further discoveries are likely. NASA has not yet announced a timeline for the release of additional findings.