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Title: Active Cryovolcanism on Europa?
Author: William B. Sparks, Britney E. Schmidt, Melissa A. McGrath, Kevin P. Hand, John .R. Spencer, Misty Cracraft, Susana E. Deustua

Evidence for plumes of water on Europa has previously been found using the Hubble Space Telescope (HST) using two different observing techniques. Roth et al. (2014) found line emission from the dissociation products of water. Sparks et al. (2016) found evidence for off-limb continuum absorption as Europa transited Jupiter. Here, we present a new transit observation of Europa that shows a second event at the same location as a previous plume candidate from Sparks et al. (2016), raising the possibility of a consistently active source of erupting material on Europa. This conclusion is bolstered by comparison with a nighttime thermal image from the Galileo Photopolarimeter-Radiometer (PPR) which shows a thermal anomaly at the same location, within the uncertainties (Spencer et al. 1999). The anomaly has the highest observed brightness temperature on the Europa nightside. If heat flow from a subsurface liquid water reservoir causes the thermal anomaly, its depth is ~1.8-2 km, under simple modeling assumptions, consistent with scenarios in which a liquid water reservoir has formed within a thick ice shell. Models that favour thin regions within the ice shell that connect directly to the ocean, however, cannot be excluded, nor modifications to surface thermal inertia by subsurface activity. Alternatively, vapour deposition surrounding an active vent could increase the thermal inertia of the surface and cause the thermal anomaly. This candidate plume region may offer a promising location for an initial characterization of Europa's internal water and ice and for seeking evidence of Europa's habitability.

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Hubble Spots Possible Venting Activity on Europa

Best Evidence Yet for Reoccurring Water Vapor Plumes Erupting from Jupiter's Moon
When Galileo discovered Jupiter's moon Europa in 1610, along with three other satellites whirling around the giant planet, he could have barely imagined it was such a world of wonder.
This revelation didn't happen until 1979, when NASA's Voyager 1 and 2 flew by Jupiter and found evidence that Europa's interior, encapsulated under a crust of ice, has been kept warm over billions of years. The warmer temperature is due to gravitational tidal forces that flex the moon's interior - like squeezing a rubber ball - keeping it warm. At the time, one mission scientist even speculated that the Voyagers might catch a snapshot of geysers on Europa.

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Europa: Our best shot at finding alien life?

After two decades of development and "heartbreak", scientists are on the verge of sending missions to explore the ocean world of Europa. Could this be our best shot at finding life elsewhere in the Solar System?
Orbiting the giant planet Jupiter is an icy world, just a little smaller than Earth's moon.
From a distance, Europa appears to be etched with a nexus of dark streaks, like the product of a toddler's chaotic scribbling.

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Europa Plumes
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Title: Probing for Evidence of Plumes on Europa with HST/STIS.
Author: W. B. Sparks, K. P. Hand, M. A. McGrath, E. Bergeron, M. Cracraft, S. E. Deustua

Roth et al (2014a) reported evidence for plumes of water venting from a southern high latitude region on Europa - spectroscopic detection of off-limb line emission from the dissociation products of water. Here, we present Hubble Space Telescope (HST) direct images of Europa in the far ultraviolet (FUV) as it transited the smooth face of Jupiter, in order to measure absorption from gas or aerosols beyond the Europa limb. Out of ten observations we found three in which plume activity could be implicated. Two show statistically significant features at latitudes similar to Roth et al, and the third, at a more equatorial location. We consider potential systematic effects that might influence the statistical analysis and create artifacts, and are unable to find any that can definitively explain the features, although there are reasons to be cautious. If the apparent absorption features are real, the magnitude of implied outgassing is similar to that of the Roth et al feature, however the apparent activity appears more frequently in our data.

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Europa
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Europa moon 'spewing water jets'

Further evidence has been obtained to show that Jupiter's icy moon Europa throws jets of water out into space.
Scientists first reported the behaviour in 2013 using the Hubble telescope, but have now made a follow-up sighting.
It is significant because Europa, with its huge subsurface ocean of liquid water, is one of the most likely places to find microbial life beyond Earth.

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NASA's Hubble Spots Possible Water Plumes Erupting on Jupiter's Moon Europa

Astronomers using NASA's Hubble Space Telescope have imaged what may be water vapour plumes erupting off the surface of Jupiter's moon Europa. This finding bolsters other Hubble observations suggesting the icy moon erupts with high-altitude water vapour plumes.
The observation increases the possibility that missions to Europa may be able to sample Europa's ocean without having to drill through miles of ice.

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NASA to Hold Media Call on Evidence of Surprising Activity on Europa

NASA will host a teleconference at 2 p.m. EDT Monday, Sept. 26, to present new findings from images captured by the agencys Hubble Space Telescope of Jupiters icy moon, Europa.
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NASA Research Reveals Europa's Mystery Dark Material Could Be Sea Salt

NASA laboratory experiments suggest the dark material coating some geological features of Jupiter's moon Europa is likely sea salt from a subsurface ocean, discolored by exposure to radiation. The presence of sea salt on Europa's surface suggests the ocean is interacting with its rocky seafloor -- an important consideration in determining whether the icy moon could support life.
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Cassini Search Finds No Europa Atmospheric Plumes

Recent analysis of data collected by NASA's Cassini spacecraft during its 2001 flyby of Jupiter sheds new light on the atmosphere of the planet's moon Europa. Results show that recently discovered gas plumes on Europa do not contribute to the thin atmosphere, said PSI Senior Scientist Amanda Hendrix, a co-author on a paper titled "A New Understanding of the Europa Atmosphere and Limits on Geophysical Activity."
While it is certainly possible - even likely - that plume activity occurs, it was at a level too low to be detectable by Cassini's ultraviolet imaging spectrograph, or UVIS, Hendrix said.

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Scientists Find Evidence of 'Diving' Tectonic Plates on Jupiter's Moon Europa

Scientists have found evidence of plate tectonics on Jupiter's moon Europa. This indicates the first sign of this type of surface-shifting geological activity on a world other than Earth.
Researchers have clear visual evidence of Europa's icy crust expanding. However, they could not find areas where the old crust was destroyed to make room for the new. While examining Europa images taken by NASA's Galileo orbiter in the early 2000s, planetary geologists Simon Kattenhorn, of the University of Idaho, Moscow, and Louise Prockter, of the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, discovered some unusual geological boundaries.

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