For years, the biggest question about Mars has been, “If the planet once had rivers, lakes, and maybe even oceans, where did all that water go?” happened. A new international study points to a hitherto overlooked “suspect.”
A team led jointly by the Andalusian Institute for Astrophysics (IAA-CSIC) and the University of Tokyo has proven that an intense but localized dust storm observed in Mars year 37 was capable of transporting water vapor into the upper atmosphere during the northern hemisphere summer. In a season that was thought to be “calm” in terms of water loss, the planet was much more active than expected.
A Small Storm with a Giant Effect
The storm was detected in the Syrtis Major region and covered an area of approximately 1.2 million square kilometers. It was not one of those global storms that cover the entire planet, but it was strong enough to rearrange the atmosphere.
Combining data from the ExoMars Trace Gas Orbiter, NASA’s Mars Reconnaissance Orbiter, and the Emirates Mars Mission, the team saw water vapor rocketing to altitudes of 60 to 80 kilometers. At these altitudes, the amount of water increased to ten times normal, and it did not remain a local “spot” but quickly spread around the planet. A few weeks later, it was observed that the amount of hydrogen in the exobase, the region where the atmosphere meets space, increased 2.5 times compared to the same season in previous years. This hydrogen comes from the splitting of water molecules, and once it reaches that height it’s only a matter of time before it escapes into space.
To estimate how much water Mars is losing, scientists measure exactly this escaping hydrogen. Current figures suggest that enough water has escaped into space to cover the planet’s surface at a depth of hundreds of meters.
Until now, the main “timer” for this escape was thought to be the hotter and dustier summers of the southern hemisphere; Here, global storms dragged the atmosphere upward, carrying water with them. Northern summer was considered a calm period when water vapor was trapped in the lower layers.
This study disrupts this scheme. It shows that a short but intense regional storm can trigger vertical water transport even in a season considered calm. In the words of co-author Adrián Brines, these results “open a new way to understand how Mars lost much of its water.” In practice, this means that Mars climate models must account for not just massive events, but also such small but impactful events that could lead to a significant cumulative loss of water over billions of years.
A Planet Puzzle That Has Not Yet Been Solved
The surface of Mars bears traces of a much wetter past. Dried stream beds, hydromorphic minerals, and still-observed ice deposits point to a planet not unlike today’s frozen desert. Some of this water is trapped underground and in the polar ice caps today, but other part is no longer there.
While this study doesn’t offer the definitive answer, it adds a crucial piece to the puzzle: It shows that even small storms can open temporary “windows” through which water can easily escape.
