Scientists Say Mars Lost Water During a Season They Once Thought Was Mostly Quiet

Key Points:

• A localized Martian dust storm during Martian Year 37 (2022–2023) lifted water vapor into the middle atmosphere at levels up to ten times higher than usual, challenging previous assumptions that only global storms significantly impact water escape.
• This storm occurred in the Northern Hemisphere summer, a period not typically associated with strong atmospheric water loss, suggesting that water escape mechanisms may operate under a broader range of seasonal conditions.
• Increased hydrogen levels detected at the exobase following the storm indicate enhanced water loss, as hydrogen escapes more readily when water molecules split apart, with hydrogen concentrations about 2.5 times higher than in previous years.
• The study, based on data from multiple missions including the ExoMars Trace Gas Orbiter and NASA’s Mars Reconnaissance Orbiter, highlights the importance of smaller, localized storms in Mars' long-term climate evolution and water loss.
• These findings provide new insights into how Mars lost much of its water over time, revealing that short but intense atmospheric events play a significant role beyond the previously emphasized global dust storms.