Mars, once a planet teeming with vast amounts of water, is now a dry, desolate landscape. The evidence for this transformation lies in the planet’s surface features, which suggest that water once flowed freely. Over the past 3 billion years, some of that water has seeped deep underground. But what happened to the rest? This question has puzzled scientists for years. Thanks to NASA’s Hubble Space Telescope and the Mars Atmosphere and Volatile Evolution (MAVEN) missions, we’re now closer than ever to unraveling this mystery. John Clarke, a researcher at Boston University’s Center for Space Physi…