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takyon writes:

At a NASA press conference on Thursday, scientists from the Jet Propulsion Laboratory, NASA's D.C. Headquarters, and the Space Telescope Science Institute announced new observations about the "ocean worlds" Enceladus and Europa. At Enceladus, one of Saturn's moons, the Cassini spacecraft has measured emissions of hydrogen gas that could indicate a source of chemical energy for life forms. 2016 Hubble observations of Jupiter's moon Europa have found evidence of a water plume emanating from the same location as a plume measured in 2014.

The Cassini spacecraft took a "deep dive" into one of the Enceladus plumes on Oct. 28, 2015. The plume contains about 98% water, 0.4-1.4% hydrogen, and a mixture of carbon dioxide, methane, ammonia, and other molecules. The findings support the conclusion of hot water interacting with rock at hydrothermal vents on the seafloor, a type of habitat known to support life without the need for sunlight. NASA scientists have concluded that Enceladus has all of the conditions and ingredients necessary to support life, although the detection of hydrogen gas does not prove that the internal ocean currently contains life forms, and phosphorus and sulfur have yet to be measured.

The new Hubble images of Europa show that the height of the plume is about twice that of the one measured in 2014. The location of this periodic plume corresponds with a thermal hotspot on Europa's surface found by the Galileo spacecraft in the 1990s, which was once dismissed as an anomaly. The lack of craters on Europa's surface indicates that water is spraying out of the internal ocean through cracks and reshaping the surface. However, Europa's ice shell is thought to be thicker than that of Enceladus, with water vapor escaping the crust less often. NASA is currently developing a Europa Clipper mission that would conduct a series of 45 or more flybys of Europa, with the possibility of flying directly through water vapor plumes for sampling. The European Space Agency's Jupiter Icy Moons Explorer will study Europa and Callisto, but end its mission by orbiting Ganymede.

The same chemistry detected at Enceladus could also be taking place in interior oceans on other icy worlds, such as Ceres, Titan, Ganymede, Callisto, Dione, Rhea, Titania, Triton, Pluto, Eris, Sedna, etc.

Here's the press briefing (48m16s). Also at Science Magazine, BBC, Space.com, and Popular Mechanics (mhajicek's link).

Cassini finds molecular hydrogen in the Enceladus plume: Evidence for hydrothermal processes (open, DOI: 10.1126/science.aai8703) (DX)

Active Cryovolcanism on Europa? (DOI: 10.3847/2041-8213/aa67f8) (DX)

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takyon writes:

Plate tectonics on Jupiter's moon Europa could make finding life there more likely:

Earthquakes could be fueling life on Europa, one of Jupiter's moons. Scientists have shown that huge chunks of the moon's ice crust could be sinking others, infusing its underground ocean with chemical food. [...] Geophysicists from Brown University in Providence, Rhode Island, have shown that tectonic activity is also feasible within Europa's ice shell. They used a computer simulation to map subduction—where one giant slab of ice is forced under another.

The gravitational pull of moons could extend the unfrozen lifetime of subsurface oceans on some objects, such as Pluto and Charon:

Heat generated by the gravitational pull of moons formed from massive collisions could extend the lifetimes of liquid water oceans beneath the surface of large icy worlds in our outer solar system, according to new NASA research. This greatly expands the number of locations where extraterrestrial life might be found, since liquid water is necessary to support known forms of life and astronomers estimate there are dozens of these worlds.

"These objects need to be considered as potential reservoirs of water and life," said Prabal Saxena of NASA's Goddard Space Flight Center in Greenbelt, Maryland, lead author of the research published in Icarus [DOI: 10.1016/j.icarus.2017.11.023] [DX] November 24. "If our study is correct, we now may have more places in our solar system that possess some of the critical elements for extraterrestrial life."

List of largest lakes and seas in the Solar System.

Also at Brown University (EurekAlert).

Porosity and salt content determine if subduction can occur in Europa's ice shell (open, DOI: 10.1002/2017JE005370) (DX)

Original Submission

takyon writes:

While water plumes have been imaged on Saturn's icy moon Enceladus by the Cassini spacecraft, evidence for plumes on Jupiter's moon Europa has been scarce. But a new analysis found that a magnetometer aboard the Galileo spacecraft recorded signs of a plume in 1997, years before the Cassini spacecraft encountered plumes:

Scientists have new evidence that there are plumes of water erupting from the surface of Jupiter's icy moon Europa — plumes that could, maybe, possibly contain signs of life. The evidence comes from data collected by the now-defunct Galileo spacecraft. Although the data has been available since it was collected in 1997, it's only now that an analysis confirms the existence of water plumes.

For more than two decades, scientists have been convinced Europa has a liquid water ocean sloshing around beneath its icy outer crust. In the past six years, two teams of researchers using the Hubble Space Telescope reported the possible existence of plumes. But as powerful as Hubble is, seeing something as small as a plume on a moon more than 380-million miles away is difficult. "We're looking for effects that are relatively small, and are pushing the spatial resolution of the telescope," says astrophysicist Susana Deutsua of the Space Telescope Science Institute.

Congressman John Culberson, known for his support for the Europa Clipper mission, broke the research embargo in a recent hearing on NASA's budget.

Also at Ars Technica and The Verge.

Evidence of a plume on Europa from Galileo magnetic and plasma wave signatures (open, DOI: 10.1038/s41550-018-0450-z) (DX)

Original Submission

Phoenix666 writes:

Phys.org:

The study of two potential plume sites on Jupiter's moon Europa has shown a lack of expected hotspot signatures, unlike Enceladus where plumes have a very clear and obvious temperature signature, research by Planetary Science Institute Senior Scientist Julie Rathbun shows.

"We searched through the available Galileo thermal data at the locations proposed as the sites of potential plumes. Reanalysis of temperature data from the Galileo mission does not show anything special in the locations where plumes have possibly been observed. There are no hotspot signatures at either of the sites," Rathbun said. "This is surprising because the Enceladus plumes have a clear thermal signature at their site of origin, so this suggests that either the Europa plumes are very different, or the plumes are only occasional, or that they don't exist, or that their thermal signature is too small to have been detected by current data."

Original Submission

Phoenix666 writes:

CNet:

Europa, the fourth-biggest moon orbiting gas giant Jupiter, hides a salty, liquid ocean underneath its icy shell and thus, may harbor the ingredients necessary for life. A new study has found that Europa's surface is full of sodium chloride -- table salt -- and concludes the hidden ocean underneath Europa's ice may be more similar to Earth's oceans than previously imagined.

The study, published Wednesday in Science Advances by researchers at Caltech and NASA's Jet Propulsion Laboratory, show for the first time how yellow patches on Europa's surface, first noticed by NASA proves Voyager and Galileo decades ago, actually indicate the presence of sodium chloride.

Excellent! The astronaut who catches the first Europan fish won't have to send away for seasoning.

Also at Caltech.

Sodium chloride on the surface of Europa (open, DOI: 10.1126/sciadv.aaw7123) (DX)

Original Submission

upstart writes in with an IRC submission:

Jupiter's ocean moon Europa probably glows in the dark:

The icy Jupiter moon Europa is an astrobiological beacon, quite literally glowing in the deep darkness far from the sun, a new study suggests.

Jupiter's intense radiation environment likely lights up Europa's icy shell, which overlies a huge, potentially habitable ocean of salty liquid water, researchers have found.

"If Europa weren't under this radiation, it would look the way our moon looks to us — dark on the shadowed side," study lead author Murthy Gudipati, a scientist at NASA's Jet Propulsion Laboratory (JPL) in Southern California, said in a statement. "But because it's bombarded by the radiation from Jupiter, it glows in the dark."

[...] "But we never imagined that we would see what we ended up seeing," study co-author Bryana Henderson, also of JPL, said in the same statement. "When we tried new ice compositions, the glow looked different. And we all just stared at it for a while and then said, 'This is new, right? This is definitely a different glow?' So we pointed a spectrometer at it, and each type of ice had a different spectrum."

This nightside glow — it won't be visible on Europa's sun-illuminated dayside — has more than just gee-whiz appeal. Its color and intensity could reveal key details about the composition of the moon's icy shell, study team members said.

Original Submission