A significant portion of Mars' water, probably between 30 and 99 per cent, is still trapped within minerals in the planet's crust, says a new study published in the journal Science, challenging the previously known theory that the Red Planet's water escaped into space.
The research team from California Institute of Technology (Caltech) and NASA's Jet Propulsion Laboratory (JPL) found that four billion years ago, Mars had enough water to have covered the whole planet in an ocean of about 100 to 1,500 metres deep, a volume roughly equivalent to half of Earth's Atlantic Ocean. However, a billion years later, the planet turned dry as it is today, they said.
In the past, it was widely believed by scientists who sought to explain what happened to the flowing water on Mars suggesting that it escaped into space, becoming victim of Mars's low gravity. Though some water was lost on Mars this way, it now appears that such evaporation cannot account for the loss of most of the water on Mars.
"Atmospheric escape does not fully explain the data that we have for how much water actually once existed on Mars," said lead author of the study Eva Scheller, a PhD candidate at Caltech. "All of this water was sequestered fairly early on, and then never cycled back out," Scheller said.
The team studied the quantity of water on Mars over time in all its forms (vapour, liquid, and ice) and the chemical composition of the planet's current atmosphere and crust through the analysis of meteorites as well as using data provided by Mars rovers and orbiters, looking in particular at the ratio of deuterium to hydrogen (D/H).
"Atmospheric escape clearly had a role in water loss, but findings from the last decade of Mars missions have pointed to the fact that there was this huge reservoir of ancient hydrated minerals whose formation certainly decreased water availability over time," said study coauthor Bethany Ehlmann, Professor at California Institute of Technology.
The research, which relied on data from meteorites, telescopes, satellite observations, and samples analysed by rovers on Mars, illustrates how multiple ways of probing the Red Planet can throw up new results, she said.
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