Billions of years ago, geological evidence suggests that the cold and dry Red Planet used to be far more blue. There was enough water collected into pools, lakes, and deep oceans to have covered the whole planet in an ocean roughly 100 to 1,500 meters (330 to 4,920 feet) deep. That is roughly equivalent to half of Earth’s Atlantic Ocean.?
The question is: what exactly happened to all that water??
While some water can be found frozen in the Martian polar ice caps, scientists had previously suggested that the flowing water on Mars escaped into space due to the planet’s low gravity. And while some water did indeed leave Mars this way, a new NASA-backed study claims that a large quantity of its water is still on the planet, trapped in its crust.?
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"Atmospheric escape doesn't fully explain the data that we have for how much water actually once existed on Mars," Eva Scheller, the lead author of the paper that was published in the journal Science, said.?
Scheller and his colleagues used data from Mars’ rovers and orbiters as well as analysed meteorites to study the quantity of water the Red Planet had in the beginning and how much it lost over time.?
One way to do that is by analysing the hydrogen levels within the planet’s atmosphere and rocks. Water is made up of both hydrogen and oxygen, but not all hydrogens atoms are created equal. Most of them have just one proton within the atom’s nucleus, whereas the so-called "heavy" hydrogen, have an additional neutron.?
Regular hydrogen has little trouble escaping from a planet's gravity than heavier deuterium. The ratio of deuterium to hydrogen (D/H) in the planet’s atmosphere, therefore, reflects the loss of Martian water.?
"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," explains Bethany Ehlmann, professor of planetary science and associate director for the Keck Institute for Space Studies.?
When water and rock come together, a process called chemical weathering can take place forming clays and other hydrous minerals that contain water as part of their mineral structure.?
And while Mars still has between 30 per cent and 99 per cent of its water trapped in the crust, Scheller cautions that it won’t be easy for future astronauts to easily extract water for their use.?