PASADENA, California / TOKYO — April 22, 2026 — In a historic announcement that rewrites our understanding of the Red Planet, NASA and the Japan Aerospace Exploration Agency (JAXA) today revealed definitive evidence of a massive ancient ocean on Mars. Using combined data from the Perseverance rover, the Mars Reconnaissance Orbiter, and JAXA’s MMX (Martian Moons eXploration) spacecraft, scientists have mapped what they call the “Deuteronilus Ocean” — a body of water that covered nearly 30% of the Martian surface approximately 3.5 billion years ago.

The findings, published simultaneously in Science and Nature Astronomy, represent the strongest indication yet that early Mars was warm, wet, and potentially habitable for extended periods. “We have identified unmistakable sedimentary deposits, delta formations, and paleoshorelines that extend for thousands of kilometers,” said Dr. Alyssa Carson, lead NASA planetary scientist. “This ocean was not a transient flood — it persisted for millions of years, providing a stable environment where microbial life could have emerged.”

🔬 How Scientists Uncovered the Hidden Ocean

The breakthrough came from combining ground-penetrating radar from the MMX orbiter with high-resolution spectral imaging from NASA’s CRISM instrument. The radar revealed distinct stratigraphic layers characteristic of ancient seabeds — cross-bedding, ripple marks, and erosional channels. Meanwhile, Perseverance’s SHERLOC and PIXL instruments detected carbonate-rich rocks and sulfates that form exclusively in subaqueous environments. “We see the same geological signatures that on Earth indicate shallow marine shelves,” explained Dr. Kenji Tanaka, JAXA project scientist. “The evidence is overwhelming.”

The ocean is believed to have existed during the Noachian-Hesperian transition, a period when Mars’ magnetic field weakened and its atmosphere began escaping into space. Climate models suggest that volcanic outgassing and a thicker CO₂ greenhouse once allowed liquid water to pool in the northern basin. Over time, as the planet cooled and lost its magnetic shield, the ocean froze and sublimated, leaving behind vast salt flats and the polar ice caps we see today.

🧪 Implications for Extraterrestrial Life

Perhaps most tantalizing is the discovery of complex organic molecules within ancient seabed samples. Perseverance drilled cores from a region named “Ariel Basin,” revealing fatty acids and polycyclic aromatic hydrocarbons — building blocks of life as we know it. While these compounds can form abiotically, their association with sedimentary structures and redox gradients suggests biological origins cannot be ruled out. “We are not claiming to have found fossils,” cautioned Dr. Carson. “But we have found precisely the type of chemical and mineralogical signatures that on Earth would be interpreted as biosignatures.”

NASA and JAXA have now prioritized the Mars Sample Return mission, scheduled for launch in 2028, to bring these cores back to Earth for advanced analysis. “If microbial life ever emerged on Mars, these samples will contain the evidence,” said Thomas Zurbuchen, former associate administrator of NASA’s Science Mission Directorate. “We are closer than ever to answering humanity’s deepest question: are we alone?”

🛰️ International Collaboration and What Comes Next

The joint NASA-JAXA announcement has energized the global planetary science community. The European Space Agency’s ExoMars Rosalind Franklin rover, set to land in 2027, will target similar paleo-ocean sediments in Oxia Planum. China’s Tianwen-3 mission also plans to investigate northern lowland sites. “This discovery transforms Mars exploration from ‘follow the water’ to ‘explore the ancient seafloor’,” noted Dr. Zita Martins, astrobiologist at Instituto Superior Técnico, Lisbon.

In the immediate term, Perseverance will traverse towards the newly mapped shoreline to collect additional samples from distinct facies. Meanwhile, MMX will continue radar mapping to refine ocean depth models — early estimates suggest maximum depths of 1.5 kilometers. The international science team will also release an interactive 3D map of the ancient ocean for public access next month.

🌎 Earth Connections: Climate Lessons from Mars

Understanding how Mars lost its ocean has direct implications for Earth’s long-term climate stability. The Red Planet serves as a natural laboratory for runaway greenhouse effects and atmospheric escape processes. “Mars shows us what happens when a planet’s magnetic shield collapses and solar wind strips away a thick atmosphere,” said Dr. David Brain, planetary scientist at LASP. “It underscores the importance of Earth’s protective magnetosphere and the delicate balance that sustains liquid water on our world.”

The discovery also adds urgency to protecting our own oceans from climate change. While Mars’ ocean vanished over eons due to planetary-scale forces, Earth’s marine ecosystems are threatened by warming, acidification, and pollution on human timescales. “Mars is a cautionary tale,” reflected Dr. Carson. “But it’s also a story of resilience — and a reminder that water, life’s essential solvent, may be more common in the universe than we ever imagined.”

This story is breaking and will be updated. Global Discovery News will provide ongoing coverage as new data emerges from Mars orbiters and rover missions. Additional reporting from NASA JPL, JAXA’s Sagamihara Campus, and international astrobiology conferences.

🗺️ Explore the Ancient Ocean: Interactive Map & Sample Details →

Credits & sources: NASA Planetary Science Division, JAXA Institute of Space and Astronautical Science, peer-reviewed studies: Science (Vol. 392, Issue 6541) and Nature Astronomy (April 2026). Data from Perseverance Rover Mission Sol 1,245–1,310.