Mars Water Mystery: Escaped to Space, Hidden Deep Underground

Mars was once wet, with rivers and possibly an ocean, but two fates explain its drying: much water vapour escaped to space after the magnetic shield faded, while a newer view suggests a deep, crustal reservoir could still hold vast amounts of water — possibly enough to flood the planet if released. MAVEN confirms ongoing atmospheric loss, but the deep-water interpretation remains debated and not yet proven; Perseverance’s Jezero samples could test past habitability, and future seismic or drilling missions would be needed to confirm buried stores.