Jacklin Kwan, 16 November 2022.

Excerpt:

>Martin Bizzarro at the University of Copenhagen in Denmark and his colleagues have analysed the concentration of a rare chromium isotope, known as chromium-54, in samples of meteorites that have come to Earth from Mars to estimate how much water was deposited on the Red Planet by asteroids.

>“It’s a bit like DNA,” says Bizzarro. “Carbonaceous-type asteroids have a very distinct chromium isotope composition relative to the inner solar system.”

> 

>If the original bombarding asteroids were just 10 per cent water, the lower limit for C-type meteorites, they would have deposited enough of the molecule to create a global ocean, say the researchers. If spread out over the whole planet, the water would form a layer 300 metres deep.

>“I think this is the first time where we have a smoking gun,” says Bizzarro, and we can finally say with certainty that water-rich asteroids hit Mars’s surface.

>C-type asteroids also contain elements that are essential to life.

>This means that two of the most important ingredients necessary to life – organic molecules and water – were present on Mars during a time before Earth’s moon even formed, say the researchers.

Science Advances, DOI 10.1126/sciadv.abp8415