Comet Hartley 2, photographed close up by NASA's EPOXI mission in 2010, offers new clues about the origin of the water in the Earth's Oceans. Photo Credit/NASA photo
Scientists have compelling new evidence the Earth’s oceans formed from the impact of comets during the early years of the solar system, and quite likely a specific class of the icy objects from a region known as the Kuiper Belt
Tenants of the Kuiper Belt include the dwarf planet Pluto and many similar objects as well as innumerable comets that swoop from their “homeland” hundreds of millions of miles away, toward and around the sun.
The connection between these bodies and the Earth was established by the European Space Agency space telescope, Hershel, which was launched in May 2009.
Observations of the comet Hartley 2 with the large infrared observatory surprised astronomers by revealing a characteristic chemical signature. Hartley 2 was comprised of half as much “heavy water” as other comets.
Heavy water is H2O like normal water, but one of the two hydrogen atoms is more massive than the other. Chemists call the heavier hydrogen deuterium.
The curious ratio matches the ratio of “heavy” water to normal water on the Earth.
By studying Hartley 2’s celestial path, astronomers established the object’s origins as the Kuiper Belt, rather than another immense source for comets, the Oort Cloud.
Hartley 2 passes through the inner solar system every 6 1/2 years.
“Our results with Herschel suggest that comets could have played a major role in bringing vast amounts of water to an early Earth,” said Dariusz Lis, senior research associate in physics at the California Institute of Technology in Pasadena and co-author of a new paper in the journal Nature. “This finding substantially expands the reservoir of Earth ocean-like water in the solar system to now include icy bodies originating in the Kuiper Belt.”
If Lis and his colleagues are correct, the Earth emerged from the early formation of the solar system about 4.5 billion years ago, hot, dry and not very suitable for life. But in the chaos of that early period, comets pounded the inner solar system. When they struck the Earth, the icy objects melted into the oceans. The prospects for the emergence of life improved greatly.