New observations from the Hubble Space Telescope show jets of water vapour blasting off the southern pole of Europa, an ice-covered moon of Jupiter believed to hold an underground ocean. If confirmed, the discovery could affect scientists' assessments of whether the moon has the right conditions for life, planetary scientist Kurt Retherford, with the Southwest Research Institute in San Antonio, Texas, said at the American Geophysical Union conference in San Francisco. "We've only seen this at one location right now, so to try to infer that there's a global effect as a result of this is a little difficult at this time." Researchers using the Hubble Space Telescope found 200-kilometre-high plumes of water vapour shooting off from Europa's south polar region last December. The jets were not seen during Hubble observations of the same region in October 1999 and November last year. The now-defunct Galileo spacecraft, which made nine passes by Europa in the late 1990s, likewise did not detect any plumes. Scientists believe the water vapour may be escaping from cracks in Europa's southern polar ice that open due to gravitational stresses when the moon is farthest from Jupiter. The plumes could also be the result of frictional heating from rubbing ice blocks or a fortuitously timed comet impact, scientists said. Similar jets have been detected on Saturn's moon Enceladus which, because it has only one twelfth the gravity of Europa, can shoot its plumes much farther. Additional Hubble observations are planned, as well as a review of archived Galileo data taken when Europa was farthest away from Jupiter.