Rosetta Spacecraft Suggests Asteroids, Not Comets, Birthed Earth's Oceans
Ice on comet 67P displays chemistry unlike seawater, the spacecraft circling overhead reveals.
Asteroids, not comets, likely delivered Earth's ancient oceans from space, concludes a Wednesday study from the Rosetta spacecraft, now in orbit around a comet that is a frozen relic from the dawn of the planets.
Where did the Earth's oceans come from? the new study asks, investigating a long-debated question of whether the water on our planet's surface was delivered during a bombardment of comets some 3.8 billion years ago. Not likely, mission scientists conclude, pointing instead to ancient asteroids, which were covered with frost in the early solar system.
"Terrestrial water was probably brought by asteroids," says Rosetta study leader Kathrin Altwegg of the University of Bern in Switzerland. She finds that source "more likely than comets."