Mars, the Red Planet, has long been a subject of mystery and intrigue. For decades, scientists have wondered whether life once thrived on this barren landscape or if it’s now a desolate wasteland. Another puzzle is where all the water went. Once, Mars had an abundance of water, but three billion years ago, it began to dry up.
Recent studies suggest that Mars’ lost water may not have retreated underground or sublimed away into space entirely. Instead, two new papers propose that the answer lies in both. The first study, published in the Proceedings of the National Academy of Sciences, analyzed data from the Mars InSight spacecraft and concluded that a soggy subsurface contains enough water to cover the entire planet.
The second study, published in Science Advances, relied on data from NASA’s Hubble Space Telescope and MAVEN orbiter. These spacecraft gathered information about the Martian atmosphere, specifically the escape of hydrogen to space over the past decade for MAVEN and 33 years for Hubble. The researchers tracked the escape of ordinary hydrogen and deuterium (a heavier form of hydrogen) into space.
The study found that light hydrogen streams away from Mars easily, but deuterium has a harder time due to its additional particle in its nucleus. This means that more water molecules broke down into hydrogen atoms, which then escaped into space. The researchers estimate that tens to hundreds of meters of the mile-deep layer of water may have escaped to space.
The team also discovered that Mars’ irregular orbit affects the amount of water in the atmosphere and the escape rate of hydrogen. At aphelion (the point farthest from the sun), there’s less than one part per million of water in the skies, while at perihelion (the closest approach), there’s more than 50 parts per million.
According to John Clarke, professor emeritus of astronomy at Boston University’s Center for Space Physics, “The whole atmosphere is very turbulent, heating up and cooling down on short timescales, even down to hours. The atmosphere expands and contracts as the brightness of the sun at Mars varies by 40% over the course of a Martian year.”
This has significant implications, as it affects the ratio of deuterium to hydrogen in water molecules on Mars. Modern-day Mars has up to eight times more deuterium relative to light hydrogen than does Earth. Running these numbers, Clarke and his co-authors estimate that tens to hundreds of meters of the lost water may have escaped to space.
While this study provides new insights into Mars’ lost water, it still leaves many questions unanswered. However, by understanding how atoms escape into space, scientists can better comprehend the planet’s history and what happened to its water.
Source: https://time.com/7018680/where-did-all-of-mars-water-go/