For decades, planetary scientists have puzzled over a cosmic disappearance: where did the water on Mars go? While evidence from rovers like Perseverance and Curiosity confirms the Red Planet was once a lush, wet world, today it is a frozen desert.
A new study, utilizing data from six instruments across three international spacecraft, has identified a surprising culprit in this vanishing act. Researchers have discovered "rocket storms"-intense dust events that act as elevators, lifting water vapor high into the atmosphere where it is permanently destroyed.
The Mechanics of Water Loss
On Earth, water cycle processes are relatively stable. On Mars, however, the planet's thin atmosphere and elliptical orbit create more volatile conditions. Scientists use the Deuterium/Hydrogen (D/H) ratio to track water loss. Because regular hydrogen is lighter than its isotope, deuterium, it escapes into space more easily when water molecules are broken apart by solar radiation.
Previously, experts believed this "escape" happened primarily during the southern summer, when Mars is closest to the Sun. However, recent data from the ExoMars mission, the Emirates Mars Mission, and the Mars Reconnaissance Orbiter captured a massive storm during the cooler northern summer of 2022.
Breaking the Seasonal Cycle
The study reveals that dust storms heat the middle atmosphere by approximately 15 degree celcius. This localized warming prevents water ice clouds from forming. Without these clouds to trap moisture at lower altitudes, the water is pushed into the upper atmosphere. There, unprotected from ultraviolet radiation, the molecules are ripped apart, and the hydrogen is swept away by solar winds.
This finding suggests that Mars has been losing water year-round for billions of years, rather than just during specific seasons. It provides a vital missing piece of the puzzle, explaining how a planet once covered in deep oceans became the arid world we see today.
