Has it been proven by isotope analysis or any other means that the earth’s oceans came from comets?

The first isotopic analysis of a cometary coma was performed during a flyby of comet Halley by the Giotto spacecraft. These data suggest that the deuterium (heavy hydrogen)-to-hydrogen ratio (D/H) of the comet is much larger than that of the Earth’s oceans, by roughly a factor of two. Subsequent measurements of D/H ratios in comet Hale-Bopp and Hyakutake using radio astronomy appeared to support this result. The D/H ratio of the Earth seemed more consistent with the water found in carbonaceous asteroids – which is usually locked up in clay minerals. Recently the Herschel Space Observatory revealed an ocean-like ratio in the Jupiter-family comet 103P/Hartley 2, reopening the debate. We performed experiments that show that the D/H ratio in the vapor can be very different than in the comet nucleus. So, bottom line, we still have a way to go to determine whether comets or asteroids delivered the water for our oceans.