Perseverance finds buried ancient river on Mars

NASA's Perseverance rover has uncovered signs of an ancient river beneath the surface of Jezero Crater, using ground-penetrating radar to reveal buried layers of sediment left by flowing water. The channel appears to have been larger and faster-moving than many scientists expected—perhaps comparable to medium-size rivers on Earth—and adds direct subsurface evidence to the delta-like features seen from orbit.

The data suggest the river existed between 3.7 and 4.2 billion years ago and carried sand and small rocks downstream. Radar images show steep, slanted layers that typically form as water transports and deposits sediment, and the findings indicate a stable river system rather than a brief, catastrophic flood—an important point for the idea that Mars once offered conditions more favorable to simple life.

Perseverance gathered the underground data over 78 traverses with its Radar Imager for Mars Subsurface Experiment, or Rimfax, sending radio waves into the ground and interpreting the echoes that bounced back.

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