Earth’s Water Likely Isn’t From Comets, ESA’s Rosetta Suggests
Dec. 10 (Bloomberg) — Earth’s water probably arose internally and from nearby asteroids rather than from comets, according to the first major findings since the European Space Agency’s Rosetta mission landed the Philae probe on a comet.
Water on the surface of the comet is significantly denser than water molecules on Earth, according to a study to be published tomorrow in the journal Science. Drawing on data from Rosetta, which last month dropped the first-ever probe on a comet, the study suggests that Earth’s oceans may not have originated with the icy rocks from beyond Jupiter.
Rosetta was launched in March 2004 and has been orbiting the comet, which is between Mars and Jupiter, since Aug. 6, gleaning information about the mass of dirty ice, dust and gas. The new study points to asteroids, which originate closer to the sun than comets, and internal Earth pools as the source of the oceans, said Kathrin Altwegg, its lead author.
“The main reservoir is probably asteroids and, in principal, water in the Earth,” Altwegg, of the University of Bern in Switzerland, said in a phone interview. “What points to asteroids is this story with the late heavy bombardment, it’s craters on the moon, which showed that there was really a bombardment of the moon and of course also of the Earth.”
The craters on the moon and the first signs of water on the Earth date to about the same time, 3.8 billion years ago, Altwegg said. Scientists suspected comets were the source of the craters, and of water, after a 2010 space probe revealed a nearby comet’s water to be almost identical to that on Earth.
The latest study, which examined gas molecules being shot from the comet’s surface, suggests a different origin.
Next Steps
Rosetta’s next steps will be to look into the presence of organic molecules on the comet, as icy bodies like it may once have seeded Earth with the building blocks for life. To get the best glimpse of organic matter, possibly even amino acids, scientists will rely on the Philae lander. The craft is powered down after bouncing out of the intended, well-lit resting place it was to rely on for solar power.
Philae has been spotted lying on its side in a ditch on the comet, according to Matt Taylor, a Rosetta project scientist, who said the craft was still in hibernation. Its exact location is still being determined, he said.
“Once we get the identification of where the lander is, it will give us a better fix on what we believe the illumination conditions are and a better idea of when we would expect the lander to have sufficient illumination to be able to start charging its batteries and come back online,” Taylor said at a press conference yesterday.
He said that using “a kind of back-of-a-beer-mat calculation,” that would be “around May.”
The European Space Agency spent almost two decades building the Rosetta probe that carried the lander and maneuvering it 4 billion miles (6.5 billion kilometers) to the side of the comet, known as Churyumov-Gerasimenko, headed for the sun. The comet’s material is far older than the solar system, Altwegg said.
To contact the reporter on this story: Doni Bloomfield in New York at mbloomfiel12@bloomberg.net To contact the editors responsible for this story: Crayton Harrison at tharrison5@bloomberg.net John Lear, Andrew Pollack
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