ScienceDaily for December 20, 2010 reported on a theory of how oceans came into being on the earth.
But a recent study by an MIT planetary scientist suggests that the planetesimals themselves provided the water that created oceans. As Lindy Elkins-Tanton, the Mitsui Career Development Assistant Professor of Geology in MIT's Department of Earth, Atmospheric and Planetary Sciences, reports in a recent paper in Astrophysics and Space Science, these planetesimals contained trace amounts of water -- at least .01 to .001 percent of their total mass (scientists don't know the precise size of planetesimals, but they estimate that those that created Earth were between hundreds and thousands of kilometers in diameter). In the paper, Elkins-Tanton says it is likely that even tiny amounts of water in the planetesimals could create steam atmospheres that later cooled and condensed into liquid oceans on terrestrial planets.
