Friday, 5 September 2014

The Mystery of Europa's Vanished Geysers --"Taller than Mount Everest"


In 2013, huge active plumes containing water vapour being released from the surface of Jupiter’s moon Europa have been discovered. This sensational find was made using the NASA/ESA Hubble Space Telescope. Europa has been a focus of extraterrestrial research for some time now as there were clear indications that it harbours a liquid ocean beneath its icy crust. Now, it appears, the geysers have vanished.

Lorenz Roth of the Southwest Research Institute in San Antonio, Texas and Joachim Saur of the University of Cologne used the Hubble to prove that there is water vapour erupting near its south pole. The water plumes are in comparison to earth geysers immensely large and reach heights of approximately 200 km. Europa has a circumference of 3200 kilometers, comparable in size with the Moon.

But new Hubble observations in January and February of this year showed no signs of the massive plumes. "It could be just the way that we use the auroral emissions coming from those plumes at the UV [ultraviolet] wavelengths of light that we use with Hubble," discovery team member Kurt Retherford, of the Southwest Research Institute in San Antonio, told "These things depend on Jupiter's plasma environment," Retherford added. "Maybe there were just a lot of particles, atoms, getting excited by electrons and ions in Europa's atmosphere, more so than at other times, and [they] just lit up the plumes more than they usually do."

Retherford added that the plumes may sometimes simply be too small to see by the scientists who are relying on the Earth-orbiting Hubble to study the features on Europa, Retherford said. Another possibility Retherford noted is that the geysers don't exist, that the detection by Hubble, which was based primarily on observations the telescope made in December 2012, was an artifact or misinterpretation of some sort. "The best explanation still is plumes for that dataset, no doubt about it," he said

The existence of the plumes "is the kind of thing that could have a profound impact on how we explore Europa," Curt Niebur, outer planets program scientist at NASA headquarters, said during a NASA planetary sciences subcommittee meeting Wednesday held on Sept. 3."With an ocean that is tens of kilometers below the ice, most likely, if you can have a plume that's possibly bringing material from that ocean up to orbit, well, that's going to affect how you explore," Niebur added.

“Water is generally considered a basic prerequisite for life – at least as we know it on earth,” said Lorenz Roth, who was in charge of analysing the 2013 Hubble observations and who has been working at the Southwest Research Institute in America. “For this reason, the discovery of a water vapour plumes on the moon Europa has increasingly become a focus of extraterrestrial research.” The plumes eject material from the surface which will make further investigations of the moon Jupiter much easier in the future.

“We have been advancing the search for water and water plumes with multiple Hubble campaigns,” says Joachim Saur. “However, it was only after a camera on the Hubble Space Telescope in one of the last Space Shuttle Missions was repaired that we were able to achieve enough sensitivity to observe the fountains.”

The water plumes could only be seen in the observations when Europe was in a position in its orbit where the moon was furthest away from Jupiter. That means that the activity of the fountain varies temporally. Europa’s orbit is not quite circular but slightly elliptical. When Europa is furthest away from Jupiter in its orbit, the tidal forces cause the huge fractures in Europa’s ice surface to widen from which presumably the vapour is released.

Similar plumes of water vapour were discovered by the Cassini spacecraft on the Saturnian moon Enceladus. The activities there are similar to those on Europa during its orbit around its mother planet.

The Daily Galaxy via and

Image Credit: K. Retherford, Southwest Research Institute, NASA/ESA/K.

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