Scientists have found that localized dust storms on Mars can drive water vapor into the upper atmosphere, where it breaks apart and escapes into space. The discovery, based on observations from multiple Mars orbiters, challenges prior assumptions about when and how the planet loses water. Researchers link the effect to an intense regional storm during the Northern Hemisphere summer.
Mars, now a cold desert, once held abundant water, as evidenced by ancient channels and minerals on its surface. A key question in planetary science is how that water vanished. A new international study provides evidence that even relatively small, regional dust storms contribute significantly to this loss by lofting water vapor to altitudes where it dissociates and escapes as hydrogen into space. Adrián Brines, a researcher at Spain's Instituto de Astrofísica de Andalucía, and Shohei Aoki from Japan's University of Tokyo and Tohoku University led the work, published in Communications Earth & Environment. They analyzed data from Martian year 37, equivalent to 2022-2023 on Earth, when an unusual localized storm struck during Northern Hemisphere summer—a season not previously associated with major water escape. Observations showed water vapor in the middle atmosphere surging up to ten times normal levels. Shortly after, hydrogen at the exobase—the edge of the atmosphere—reached 2.5 times prior seasonal highs, indicating water molecule breakdown. The findings came from instruments on the European Space Agency's Trace Gas Orbiter (TGO) via its NOMAD tool on the ExoMars mission, NASA's Mars Reconnaissance Orbiter (MRO), and the Emirates Mars Mission (EMM). Brines stated, 'The findings reveal the impact of this type of storm on the planet's climate evolution and opens a new path for understanding how Mars lost much of its water over time.' Aoki added, 'These results add a vital new piece to the incomplete puzzle of how Mars has been losing its water over billions of years, and shows that short but intense episodes can play a relevant role in the climate evolution of the Red Planet.' Previously, research focused on planet-encircling storms and Southern Hemisphere summers, making this Northern event particularly surprising.