The Herschel Space Observatory reveals that the comet Hartley 2, coming from the Kuiper Belt, is composed largely of water with the same composition (chemical signature) as that of the Earth’s oceans. Hartley 2 is the first comet of the Kuiper Belt to be investigated for its composition. Other comets subjected to similar analyses had given unfavorable results (the composition of the water was not exactly that of the Earth’s oceans). Subsequent analyses of the abundance of Deuterium in the water of other comets and especially of numerous asteroids, will instead lead to the conclusion that the water of the Earth’s oceans is largely of asteroidal, and not cometary, origin.
