Ancient Rivers Discovered Beneath Martian Surface, Expanding Window for Past Life

NASA’s Perseverance rover has uncovered evidence of an ancient river system buried deep beneath the surface of Mars’ Jezero Crater, suggesting the planet may have been habitable for a longer period than previously thought. The discovery, made using ground-penetrating radar, reveals layers of sediment deposited by past water flows, potentially preserving clues to ancient Martian life.

Deeper Than Previously Imagined

Although geologists long suspected Jezero Crater once held a lake and was fed by rivers – a conclusion based on orbital imagery showing a classic delta landscape – Perseverance’s findings provide direct evidence from below the surface. The rover’s Radar Imager for Mars Subsurface Experiment (RIMFAX) has probed to depths of over 115 feet (35 meters), nearly twice as deep as previous observations, revealing steeply sloping layers indicative of sediment deposited by water. [Scientific American]

An Older System Than Expected

The newly discovered river system is even older than the surface deltas previously identified, dating back approximately 3.7 to 4.2 billion years. This suggests a more extensive and long-lasting network of rivers than scientists initially believed. The current is even thought to be strong enough to carry sand and small stones downstream. [Scientific American] This finding extends the timeframe during which Mars could have supported life, as conditions favorable for fossil preservation – such as those created by fluvial deposition – were present for a more extended period.

Implications for the Search for Life

The discovery has significant implications for future biosignature searches. Sediment deposited in water is considered a prime location to search for evidence of past life, as it can trap and preserve chemical traces. Perseverance is currently collecting samples of Martian rock and soil for potential return to Earth, where they can be analyzed with more sophisticated equipment. [NASA Science]

Evidence from Beyond Jezero Crater

This isn’t the first evidence of ancient water found beneath the Martian surface. China’s Zhurong rover, part of the Tianwen-1 mission, also used radar to detect evidence of a vast ancient ocean in the Utopia Planitia region, approximately 3,000 miles from Jezero Crater. [Science Alert] This ocean is believed to have once covered about a third of the planet’s surface. [Science Alert]

Jezero Crater: A History of Water

Jezero Crater, located in the Syrtis Major quadrangle, is approximately 45 kilometers (28 miles) in diameter. [Wikipedia] It’s believed to have been flooded with water in the past, containing a fan-delta deposit rich in clays. [Wikipedia] The crater was named after Jezero, a town in Bosnia and Herzegovina, meaning “lake” in several Slavic languages. [Wikipedia]

Future Missions and Sample Return

While NASA’s Mars Sample Return program has faced delays and cost concerns – with estimates exceeding $11 billion – efforts are underway to find modern approaches to ensure the program’s continuation. [Scientific American] Scientists are hopeful that analyzing the samples on Earth will reveal further insights into Mars’ past, including the potential for ancient microbial life. In September 2023, Perseverance identified a sample containing material resembling potential fossils, though a non-biological explanation hasn’t been ruled out. [Scientific American]