Comet Ice May Have Fed Earth's Oceans

Some of the water that covers much of the Earth may have been carried here by comets from beyond Neptune. The water in a comet called 103P/Hartley 2 is chemically very similar to water on Earth, suggesting that some of Earth's water comes from the same comet family, reports an international study led by Paul Hartogh at the Max-Planck-Institut fur Sonnensystemforschung and published last week in Nature.

103P/Hartley 2 is believed to come from the Kuiper belt beyond the orbit of Neptune. Scientists think asteroids and comets may have subsequently crashed into the Earth, transporting water in the process.