Reviewing 2013: Hubble spots Water!


Few worlds inspire the imagination quite like Europa, one of Jupiter’s largest moons. The icy crust protects a sub-surface ocean of liquid water, heated from the inside by tidal interactions with the gas giant. Spectroscopic observations of Europa’s ice reveal a dynamic interplay between the ocean and surface, leading to the theory that nutrients and oxygen can be cycled down below. All these factors have led astrobiologists to call for a mission to the moon; a mission that could reveal a Europan biosphere — potentially hosting complex organisms. Now, in new observations by the Hubble Space Telescope, plumes of water vapor have been discovered venting into space. Wouldn’t it be awesome if we could fly a spacecraft through that plume to see if any biological material has hitched a ride? Sadly, NASA’s planetary sciences budget has been slashed, likely sidelining that bold idea for many years to come.

 Scientists using the Hubble Space Telescope have found plumes of water vapor shooting off the southern pole of Europa, an ice-covered moon of Jupiter that is believed to have an underground ocean.

If confirmed — so far the plumes have only been spotted once — the finding could have implications for the moon’s suitability for life and help explain why its surface appears relatively young and crater-free.

“The plumes are incredibly exciting, if they are there. They’re bringing up material from in the ocean, perhaps there’s organic material that will be laying on the surface of the south pole. Those are the things that we want to know about,” James Green, head of NASA’s planetary science programs, told reporters at the American Geophysical Union conference in San Francisco on Thursday.

Scientists do not yet have enough information to know if the plumes are indeed stemming from Europa’s underground ocean, or if they are the result of plates of ice rubbing together and generating heat from friction, which allows some ice to vaporize.

The plumes were found when Europa was farthest away from Jupiter, a time when gravitational stresses are strongest, added Lorenz Roth, with the Southwest Research Institute in San Antonio, Texas.

“When Europa is close to Jupiter, it gets stressed and the poles get squished and the cracks close up. Then, as it moves further away from Jupiter, it becomes un-squished, the pole moves outward and that’s when the cracks open,” planetary scientist Francis Nimmo, with the University of California in Santa Cruz told Discovery News.

Using data from Hubble, scientists were able to correlate the plumes with the appearance of cracks in moon’s surface ice.

Additional observations with Hubble are planned to attempt to verify the findings. Scientists also will be re-examining archived data collected by NASA’s Galileo spacecraft, which made nine passes by Europa in the late 1990s.

“We’ll have some other great results, or another controversy,” Green said.

The Saturn-orbiting Cassini spacecraft has found similar plumes blasting off the icy moon Enceladus. The Saturn moon is much smaller and has less gravity, so its plumes shoot far higher into space. However, the density of water vapor in the moons’ plumes is remarkably similar, scientists said.

On Europa, the plumes reach an altitude of about 125 miles, fall back to the surface and freeze within about 20 minutes, Roth said.

Overall, scientists measured seven tons per second of material coming out Europa’s south solar plumes.

“That’s just an amazing amount,” said Kurt Retherford, also with the Southwest Research Institute.


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