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Practice Reading: Fill in the Blanks (Dropdown)
ID: #51230
Ocean
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Earth's surface is dominated by oceans. But where did all that water come from? and comets smashing into the early Earth have long been thought to be a promising source. But measurements of Halley's Comet and five others threw cold water on the idea that comets a large share of the oceans. Because the chemical of the comets did not match the oceans. Specifically, the ratio of heavy , or deuterium, to regular hydrogen was too high in the comets. But now astronomers have gotten a glimpse of a comet with a different origin, and it matches the oceans much better. They used the Herschel space telescope to examine Comet Hartley 2, which originated in the Kuiper Belt. Halley and its ilk came from a distant swarm of comets called the Oort Cloud. At a science meeting last week in France, and in a study in Nature, the researchers that Comet Hartley 2 has the same deuterium-to-hydrogen ratio as ocean water. So maybe comets did play a major role in delivering Earth's oceans. Something to ponder next time you have a day at the beach.
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