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NASA presents new evidence of water plumes on Europa

"Hubble’s unique capabilities enabled it to capture these plumes, once again demonstrating Hubble’s ability to make observations it was never designed to make," said Paul Hertz, director of NASA's astrophysics division.

By Brooks Hays
A composite image shows the absorption of ultraviolet wavelengths by possible water plumes at 7 o'clock on the face of Europa, just the west of its south pole. Photo by NASA/ESA/W. Sparks (STScI)/USGS Astrogeology Science Center
A composite image shows the absorption of ultraviolet wavelengths by possible water plumes at 7 o'clock on the face of Europa, just the west of its south pole. Photo by NASA/ESA/W. Sparks (STScI)/USGS Astrogeology Science Center

WASHINGTON, Sept. 26 (UPI) -- Astronomers are now more confident that water and other liquids are present on the surface of Europa, and can be collected and studied by future NASA missions without drilling through layers of ice.

The heightened confidence is the result of new evidence of water plumes, revealed by NASA scientists during a press conference on Monday afternoon.

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Over the last couple of decades, observations made by several NASA missions have hinted at the presence of a subsurface ocean on Europa, one of Jupiter's largest moons.

The latest evidence comes in the form of images collected by Hubble Space Telescope. The images show the absorption of ultraviolet wavelengths by what researchers believe are water plumes emanating from Europa's south pole.

"If there are plumes emerging from Europa, it is significant because it means we may be able to explore that ocean for organic chemicals or even signs of life without having to drill through unknown miles of ice," William Sparks, an astronomer at the Space Telescope Science Institute in Baltimore, told New Scientist.

A single image captured in 2001 by NASA's Cassini orbiter revealed similar evidence of plumes on Europa, but followup attempts failed to locate the phenomenon.

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In 2012, a team of researchers led by Lorenz Roth of the Southwest Research Institute found evidence of water vapor using Hubble. But Roth's team also found just one instance of plume activity, using a different observational strategy than did NASA scientists.

The new Hubble observations feature four separate instances of the phenomenon, captured in 2014 and 2015. On seven occasions, however, Hubble failed to find absorption of the same wavelengths. If the plumes are real, researchers say, they are intermittent -- perhaps seasonal.

Researchers detailed the additional plume images in a new paper, published this week in the Astrophysical Journal.

"Are they definitive? No. Are they compelling? Quite. Do we need missions to Europa to find out more about this beautiful little ocean world? Absolutely," Kevin Hand, one of the study's co-authors and a scientist with NASA, told National Geographic.

The best way to say for sure whether the ultraviolet phenomenon seen by Hubble is caused by water vapor expelled through cracks in Europa's ice is by direct sampling. But scientists say additional Hubble observations -- or analysis by another telescope -- could further increase the level of confidence among NASA scientists.

"Hubble's unique capabilities enabled it to capture these plumes, once again demonstrating Hubble's ability to make observations it was never designed to make," Paul Hertz, director of the astrophysics division at NASA headquarters, said in a news release. "This observation opens up a world of possibilities, and we look forward to future missions -- such as the James Webb Space Telescope -- to follow up on this exciting discovery."

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