spacetoday.net: It takes a Jupiter to raise an Earth

Posted: Sun, Feb 4, 2001, 10:43 PM ET (0343 GMT)
Gas giants like Jupiter may play a more prominent role in nurturing Earth-like habitable worlds than once thought, according to a recent study. Jonathan Lunine of the University of Arizona, in a paper published in Proceedings of the National Academy of Sciences, argues that Earth's water came not from comets from Mars-sized planetesimals flung from the asteroid belt into the inner solar system by Jupiter's powerful gravity. That conclusion is based on measurements of the ratio of deuterium to hydrogen in the Earth's oceans: those ratios do not match those measured in comets, but do match those in meteorites. If so it would imply that Earth-like worlds in other solar systems require planets not only the size of Jupiter, but in similar orbits: gas giants closer or farther away would not deliver water-rich planetesimals into terrestrial planets in the habitable zone.