Did Comets Flood Earth’s Oceans?

The Ptolemy experiment, part of the Philae lander aboard the Rosetta spacecraft, seeks to uncover clues as to whether Earth's oceans were created from water (ice) carried by comets that struck the "young" Earth. Ptolemy will analyze the types of atoms comrising Comet 67P/Churyumov-Gerasimenko's chemical mix to see how similar they are to those found on Earth. A close match could mean that comets did indeed provide much of the water found today on Earth.

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