""This was the first time ocean-like water was detected in a comet.
"We were all surprised," Bergin said.
Six other comets HiFi measured in recent years had a much different D/H ratio than our oceans, meaning similar comets could not have been responsible for more than 10 percent of Earth's water.
The astronomers hypothesize that Hartley 2 was born in a different part of the solar system than the other six. Hartley most likely formed in the Kuiper belt, which starts near Pluto at about 30 times farther from the sun than Earth is. The other six hail from the Oort Cloud more than 5,000 times farther out.
The source of earth's oceans has been a subject for debate among astronomers for decades. Until now, asteroids were thought to have provided most of the water. Now, however, Herschel has shown that at least one comet does have ocean-like water.""
http://www.sciencedaily.com/releases/2011/10/111005131654.htm
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