[aruanan]

Did the Earth form with water locked into its rocks, which then gradually leaked out..Or did the occasional impacting comet provide the Earth’s oceans?

It's been estimated that there is still about 2-3 times as much native water locked in rocks than there is free water on the surface of the earth.

[aruanan]

By analysing with Ptolemy the mix of isotopes found in Comet 67P/Churyumov-Gerasimenko, he hopes to say whether comet water is similar to that found in Earth’s oceans.

If they're similar it could also mean both the oceans on Earth and the water ice in comet 67P/Churyumov-Gerasimenko share the same origin: the primordial mess of junk out of which both the Earth and comets were formed.

[aruanan]

By analysing with Ptolemy the mix of isotopes found in Comet 67P/Churyumov-Gerasimenko, he hopes to say whether comet water is similar to that found in Earth’s oceans.

If they're similar it could also mean both the oceans on Earth and the water ice in comet 67P/Churyumov-Gerasimenko share the same origin: the primordial mess of junk out of which both the Earth and comets were formed.