PLANETARY SCIENCE:
Once, Maybe Still, an Ocean on Europa
Richard A. Kerr
BOSTON--Does the mightiest ocean in the solar system lie beneath the ice-sheathed surface of Jupiter's moon Europa? The tortured appearance of the moon's surface had persuaded many scientists, but skeptics had argued that a solid layer of ice slightly warmed by Europa's internal heat could churn slowly, reshaping the surface without ever melting. At last week's annual meeting here of the Division for Planetary Sciences of the American Astronomical Society, however, researchers presented new analyses of Europa's surface scars that had even the skeptics agreeing that, either now or in the recent past, an ocean stirred just beneath the icy surface.