Mars Once Had a Vast Ocean Covering One-Third of the Planet, New Evidence Reveals

Planet Mars. Credit: Kevin M. Gill / Flickr / CC BY 2.0

Mars has agelong raised questions astir its past. Dry riverbeds, mineral deposits, and layered rocks suggest that h2o erstwhile flowed crossed the planet. For decades, scientists person sought wide grounds that a immense water erstwhile covered Mars’ bluish plains—possibly up to one-third of the planet.

Early efforts focused connected past shorelines. Features known arsenic Arabia and Deuteronilus were thought to people the edges of a long-lost sea. But their uneven elevation formed uncertainty connected that idea. A existent shoreline should travel a accordant level. These bash not. They besides neglect to signifier a continuous bound astir the planet.

Researchers projected respective explanations. Some pointed to volcanic activity. Others suggested shifts successful the planet’s axis. None afloat resolved the problem.

“If Mars did person an ocean, it dried up a agelong clip agone – perchance respective cardinal years ago, much than fractional of the property of the satellite itself,” said Michael Lamb of the California Institute of Technology. He noted that wind, eruptions, and different forces whitethorn person erased subtle features implicit time.

Scientists displacement absorption to broader scenery patterns

A caller survey takes a antithetic approach. Instead of looking for crisp coastlines, researchers examined broader patterns crossed the Martian surface. They compared these patterns with Earth, wherever oceans permission down wide, mildly sloping regions known arsenic continental shelves.

Using planetary elevation data, the squad identified a large, low-slope set crossed Mars’ bluish lowlands. The portion lies betwixt astir minus 1,800 (5,900 ft) and minus 3,800 meters (12,500 ft). It forms a continuous portion on the bound betwixt the confederate highlands and bluish plains.

The portion aligns with cardinal geological features. Ancient stream valleys thin to prevarication supra it. Deltas and sediment deposits look wrong it. Even the debated shoreline traces autumn wrong this band.

Geological grounds supports semipermanent h2o activity

Geological findings fortify the case. Thousands of layered sediment deposits beryllium wrong the zone, immoderate of which are hundreds of meters thick. Clay minerals and altered rocks constituent to semipermanent enactment with liquid water.

New probe suggests Mars whitethorn person erstwhile hosted a immense water covering up to one-third of the planet.

Instead of wide shorelines, scientists recovered a broad, low-slope portion crossed the bluish plains—supported by sediment deposits, mineral evidence, and rover data. pic.twitter.com/nKUjOyrgjp

— Tom Marvolo Riddle (@tom_riddle2025) April 20, 2026

Delta systems successful Aeolis Dorsa and Hypanis Valles amusement repeated changes successful h2o levels. These patterns suggest that the water expanded and retreated implicit time. “The support is simply a caller reflection that ties unneurotic grounds of what the coastal portion would person looked like,” said Abdallah Zaki.

Rover information adds further support

Additional grounds comes from rover observations. China’s Zhurong rover detected sediment layers that dip successful a accordant direction. On Earth, akin structures often signifier on coastlines shaped by water.

These findings suggest semipermanent enactment betwixt h2o and land, alternatively than short-lived flooding events.

Discovery reshapes hunt for past oceans

If confirmed, the findings suggest that Mars erstwhile hosted a ample ocean that whitethorn person covered astir one-third of the planet, chiefly crossed its bluish hemisphere. Scientists judge this occurred billions of years ago, erstwhile Mars had a thicker ambiance and warmer conditions.

Researchers accidental the find could alteration however scientists hunt for past oceans. Instead of focusing connected crisp boundaries, aboriginal studies whitethorn look for wide aboveground patterns.

Upcoming missions, including the Rosalind Franklin rover, purpose to survey these regions successful detail. Scientists anticipation to larn however agelong h2o remained connected Mars and whether the satellite erstwhile supported life.