Porous Core Could be Keeping Enceladus Warm

Hydrogen Emitted by Enceladus, More Evidence of Plumes at Europa 4 comments

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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Cassini Finds Evidence of Change in Enceladus's Spin Axis 5 comments

takyon writes:

The spin axis of Saturn's moon Enceladus may have reoriented due to a collision with another body:

Saturn's icy, ocean-bearing moon Enceladus may have tipped over in the distant past, according to recent research from NASA's Cassini mission. Researchers with the mission found evidence that the moon's spin axis -- the line through the north and south poles -- has reoriented, possibly due to a collision with a smaller body, such as an asteroid.
Examining the moon's features, the team showed that Enceladus appears to have tipped away from its original axis by about 55 degrees -- more than halfway toward rolling completely onto its side. "We found a chain of low areas, or basins, that trace a belt across the moon's surface that we believe are the fossil remnants of an earlier, previous equator and poles," said Radwan Tajeddine, a Cassini imaging team associate at Cornell University, Ithaca, New York, and lead author of the paper.
[...] Whether it was caused by an impact or some other process, Tajeddine and colleagues think the disruption and creation of the tiger-stripe terrain caused some of Enceladus' mass to be redistributed, making the moon's rotation unsteady and wobbly. The rotation would have eventually stabilized, likely taking more than a million years. By the time the rotation settled down, the north-south axis would have reoriented to pass through different points on the surface -- a mechanism researchers call "true polar wander."

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Could a Dedicated Mission to Enceladus Detect Microbial Life There? 24 comments

Phoenix666 writes:

Saturn's icy moon Enceladus is best known for its numerous geysers ejecting plumes of water and ice. These eruptive fountains perplex researchers searching for signs of microbial life beyond Earth. A dedicated spacecraft designed to study the plume-like features spewing from Enceladus could definitely tell us whether or not they contain alien microorganisms.
"We need a spacecraft to travel to Enceladus, fly through a geyser plume, and analyze the water that is immediately accessible," Geoffrey Marcy, a retired professor of astronomy at the University of California, Berkeley, told Astrowatch.net.
Marcy is a renowned exoplanet researcher who discovered many extrasolar worlds. He was one of the co-investigators of NASA's Kepler planet-hunting mission that detected more than 4,000 exoworlds.
...
"The remarkable aspect of the search for microbes in the water spurting from geysers is that the spacecraft only needs to fly through the plume, well above the surface of Enceladus. No lander is needed—just a succession of flybys through the plumes as it orbits Enceladus," Marcy said.
He noted that such spacecraft should be fitted with a mass spectrometer to detect organic compounds that could be signs of microbial life. The spectrometer will look for amino acids and the structure of any organic molecules, especially fatty acids such as those composing cell membranes. It could also measure the relative amounts of isotopes of carbon (12 and 14) to detect non-natural anomalies due to biological processes.
Moreover, the mission to Enceladus would measure the properties of the water such as pH, oxidation and temperature, therefore assessing its suitability for organic life.

Marcy believes assembling "a brilliant team of billionaires" is the key to making such a mission possible. Lucky for him the monolith said nothing about Enceladus.

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How the Cassini Mission Led a 'Paradigm Shift' in Search for Alien Life 16 comments

Phoenix666 writes:

The hunt for habitable (and already inhabited) worlds has largely focused on a "Goldilocks zone" around a star, where it's neither too hot nor too cold for liquid water to exist. But astrobiologists have begun to broaden their search – thanks to discoveries by NASA's Cassini orbiter.
Saturn sits too far from the sun for its rays to melt ice, and yet Cassini discovered that one of the planet's moons, Enceladus, has a vast ocean sloshing beneath its icy crust. Instead of sunlight, tidal forces keep Enceladus's ocean warm. The gravity of Saturn pulls at Enceladus's core, driving thermal processes that create a new Goldilocks zone inside the moon itself.
"It's definitely been a paradigm shift in where you might find life," says Cassini project scientist Linda Spilker.
Still, it takes a lot more than water to make a place habitable. But here, too, Enceladus delivers. Icy geysers fueled by Enceladus's ocean shoot out from cracks in the moon's surface, allowing the Cassini spacecraft to sample them directly during flybys. What it found is that Enceladus has almost everything required for life as we know it: a source of energy, a source of carbon, and salts and minerals.

Thank goodness for Cassini, after that whole thing about being banned from Europa.

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Yuri Milner Considering Privately Funded Mission to Enceladus 6 comments

takyon writes:

Yuri Milner, the Russian billionaire backer of Breakthrough Initiatives and Breakthrough Prizes, has set his sights on Saturn's moon Enceladus:

Milner founded the $100 million Breakthrough Starshot project, an attempt to send small probes to Alpha Centauri. Now, he has announced plans to explore funding a mission to Enceladus.
[...] "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, try to see what's going on there?" Milner asked the New Space Age conference in Seattle this week.

A probe to Enceladus could be done for well under $1 billion, but it likely wouldn't be able to drill through the icy surface.

The Cassini spacecraft already flew as close as 49 km above the surface of Enceladus, and flew through a plume of water vapor released by the satellite. A proposed mission such as the Enceladus Life Finder could repeatedly fly through plumes and use better sensors to attempt to detect evidence of organic materials or microbes.

Two upcoming missions will be studying Jupiter's moon Europa: the ESA's Jupiter Icy Moons Explorer and NASA's Europa Clipper. Europa is easier for spacecraft to reach than Enceladus, but has thicker ice blocking its internal ocean.

Also at Newsweek.

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Complex Organic Molecules Found on Enceladus 4 comments

takyon writes:

Saturn moon a step closer to hosting life

Scientists have found complex carbon-based molecules in the waters of Saturn's moon Enceladus.
Compounds like this have only previously been found on Earth, and in some meteorites. They are thought to have formed in reactions between water and warm rock at the base of the moon's subsurface ocean.
Though not a sign of life, their presence suggests Enceladus could play host to living organisms. The discovery came from data gathered by the Cassini spacecraft.

Also at SwRI, ScienceAlert, Space.com, National Geographic, Popular Mechanics, and The Guardian.

Macromolecular organic compounds from the depths of Enceladus (DOI: 10.1038/s41586-018-0246-4) (DX)

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NASA Will Support Initial Concept Studies for Privately Funded Mission to Enceladus 4 comments

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

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