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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)

Original Submission #1  Original Submission #2 

takyon writes:

Timeline of Cassini–Huygens

NASA's Cassini Spacecraft Ends Its Historic Exploration of Saturn

Telemetry received during the plunge indicates that, as expected, Cassini entered Saturn's atmosphere with its thrusters firing to maintain stability, as it sent back a unique final set of science observations. Loss of contact with the Cassini spacecraft occurred at 7:55 a.m. EDT (4:55 a.m. PDT), with the signal received by NASA's Deep Space Network antenna complex in Canberra, Australia.

[...] As planned, data from eight of Cassini's science instruments was beamed back to Earth. Mission scientists will examine the spacecraft's final observations in the coming weeks for new insights about Saturn, including hints about the planet's formation and evolution, and processes occurring in its atmosphere.

[...] Cassini launched in 1997 from Cape Canaveral Air Force Station in Florida and arrived at Saturn in 2004. NASA extended its mission twice – first for two years, and then for seven more. The second mission extension provided dozens of flybys of the planet's icy moons, using the spacecraft's remaining rocket propellant along the way. Cassini finished its tour of the Saturn system with its Grand Finale, capped by Friday's intentional plunge into the planet to ensure Saturn's moons – particularly Enceladus, with its subsurface ocean and signs of hydrothermal activity – remain pristine for future exploration.

Farewell, Cassini: a 20 year mission to Saturn comes to a life-protecting end

During the Jovian flyby, Cassini performed scientific observations of the planet, showing that Jupiter's cloud belts were areas of "net-rising atmospheric motion."

This observation contradicted previous hypotheses about Jupiter's dark and light belts and served to highlight differences in planetary weather systems.

During the flyby, Cassini was also able to study Jupiter's thin ring system, revealing that Jupiter's rings were composed of irregularly shaped particles that likely originated as ejecta from micrometeorite impacts with the moons Metis and Adrastea.

Cassini: The legend and legacy of one of NASA's most prolific missions

Previously:

takyon writes:

NASA to support initial studies of privately funded Enceladus mission

NASA signed an agreement in September with a foundation to support initial studies of a privately funded mission to a potentially habitable moon of Saturn. The unfunded Space Act Agreement between NASA and the Breakthrough Prize Foundation, initiated with little public fanfare, covers NASA support for initial concept studies, known in NASA programmatic parlance as "Pre-Phase A," for a mission to the moon Enceladus, an icy world believed to have a subsurface ocean of liquid water and plumes that eject that water through the surface into space.

The agreement, the seven-page document posted on a NASA website states, "shall be for the purpose of cooperating on the Breakthrough Pre-Phase A activities for Breakthrough's Enceladus Mission." That includes supporting a series of reviews that leads up to what NASA calls Key Decision Point (KDP) A, "to determine progress to Phase A, for further formation of the Enceladus Mission's concept and technology development."

[...] Most of the study work would be done by Breakthrough. NASA, under the agreement, would use "reasonable efforts" to offer scientific and technical consulting for the study, including expertise in a range of scientific fields and in planetary projection. NASA will also advise "in the development of Phase A plans for a life signature mission to Enceladus." The agreement between NASA and Breakthrough involves no exchange of funds. NASA estimates its cost of carrying out its responsibilities under the agreement to be $72,384.

The agreement, first reported by New Scientist, offers few details about the proposed mission itself. A companion document for the agreement notes that the foundation's Breakthrough Watch program "seeks to evaluate near-term missions to objects in the Solar System, including Enceladus," that would search for signs of life there. "The Enceladus Mission is considering novel low-cost approaches, one of which uses solar sail technology to flyby the moon of Saturn to collect scientific data.

However, foundation officials have publicly discussed their interest in an Enceladus mission for a year. "We formed a little workshop around this idea," said Yuri Milner, the Russian billionaire who funds the foundation, at an event in Seattle in November 2017. "Can we design a low-cost privately-funded mission to Enceladus, which can be launched relatively soon and that can look more thoroughly at those plumes to try to see what's going on there?"

Also at Space.com.

Previously: Yuri Milner Considering Privately Funded Mission to Enceladus

Related: Underground Ocean on Enceladus May be Close to the Surface
Hydrogen Emitted by Enceladus, More Evidence of Plumes at Europa
Could a Dedicated Mission to Enceladus Detect Microbial Life There?
How the Cassini Mission Led a 'Paradigm Shift' in Search for Alien Life
Porous Core Could be Keeping Enceladus Warm
Complex Organic Molecules Found on Enceladus

Original Submission