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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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:
A study has found that a "porous"/sandy/muddy core can increase the energy released by gravitational tidal friction inside Saturn's moon Enceladus. This could explain why the interior of the icy moon has not cooled down after billions of years:
A paper published in Nature Astronomy today presents the first concept that explains the key characteristics of 500 km-diameter Enceladus as observed by the international Cassini spacecraft over the course of its mission, which concluded in September.
This includes a global salty ocean below an ice shell with an average thickness of 20–25 km, thinning to just 1–5 km over the south polar region. There, jets of water vapour and icy grains are launched through fissures in the ice. The composition of the ejected material measured by Cassini included salts and silica dust, suggesting they form through hot water – at least 90ºC – interacting with rock in the porous core.
These observations require a huge source of heat, about 100 times more than is expected to be generated by the natural decay of radioactive elements in rocks in its core, as well as a means of focusing activity at the south pole.
The tidal effect from Saturn is thought to be at the origin of the eruptions deforming the icy shell by push-pull motions as the moon follows an elliptical path around the giant planet. But the energy produced by tidal friction in the ice, by itself, would be too weak to counterbalance the heat loss seen from the ocean – the globe would freeze within 30 million years.
[...] In the new simulations the core is made of unconsolidated, easily deformable, porous rock that water can easily permeate. As such, cool liquid water from the ocean can seep into the core and gradually heat up through tidal friction between sliding rock fragments, as it gets deeper.
Powering prolonged hydrothermal activity inside Enceladus (DOI: 10.1038/s41550-017-0289-8) (DX)
Previously: Hydrogen Emitted by Enceladus, More Evidence of Plumes at Europa
Cassini Finds Evidence of Change in Enceladus's Spin Axis
Could a Dedicated Mission to Enceladus Detect Microbial Life There?
How the Cassini Mission Led a 'Paradigm Shift' in Search for Alien Life
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.
Related: NASA Releases Europa Lander Study 2016 Report
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
Cassini Spacecraft Post-Mortem
Porous Core Could be Keeping Enceladus Warm
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)
Related: Minerals In Plumes of Enceladus Indicate Hydrothermal Activity
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
Cassini Spacecraft Post-Mortem
Porous Core Could be Keeping Enceladus Warm
Yuri Milner Considering Privately Funded Mission to Enceladus
Organic Molecules Found on Ceres
NASA Finds Evidence of Water Plume on Europa
Organic Matter Found on Mars
Study Finds Evidence of More Organic Material on Ceres
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
(Score: 2) by bob_super on Thursday September 14 2017, @05:52PM (2 children)
> Enceladus has almost everything required for life as we know it: a source of energy, a source of carbon, and salts and minerals
And no humans? as soon as it gets broadband (at EU prices), I'm moving there.
That view...
(Score: 1) by fustakrakich on Thursday September 14 2017, @06:12PM (1 child)
as soon as it gets broadband (at EU prices), I'm moving there.
Latency will be a bitch...
That view...
Of what? The ice ceiling?
La politica e i criminali sono la stessa cosa..
(Score: 2) by arslan on Friday September 15 2017, @05:02AM
To earth maybe, not necessarily to europa :)
(Score: 4, Funny) by donkeyhotay on Thursday September 14 2017, @06:16PM (5 children)
I think the sentence, "contains the ingredients for life as we know it" is practically meaningless.
My kitchen, with its pantry and refrigerator contain all the ingredients for a cake. Yet every night when I return home, I find that no cake has appeared. :-)
(Score: 3, Touché) by bob_super on Thursday September 14 2017, @06:32PM (2 children)
You're just too neat and organized.
It you stored your food in a giant heated mixer instead of on shelves and in drawers, you might occasionally find that some of the resulting mess is in fact pretty good.
The metaphor is greatly helped by the quasi-certainty that Enceladus is not blessed, yet, with the presence of an Ikea.
(Score: 2) by fyngyrz on Thursday September 14 2017, @07:10PM (1 child)
Are you saying that the presence of an orbiting teapot (relatively) nearby is some kind of disincentive for Ikea?
Some people!
(Score: 2) by bob_super on Thursday September 14 2017, @07:38PM
Ikea will not come to the Saturn area, out of respect for the untouchable flat-pack superiority of those rings.
(Score: 2) by richtopia on Thursday September 14 2017, @07:57PM (1 child)
Going for a cake right out the gate is a bit aggressive. Perhaps a tortilla first which can evolve into a pastry is more probable.
Also, your lifespan is horribly short. The probability of this tortilla occurring is very low, but over 5 million years you might get something.
(Score: 3, Funny) by Osamabobama on Thursday September 14 2017, @08:32PM
Over the course of 5 million years, you might just learn to like whatever you do get.
Appended to the end of comments you post. Max: 120 chars.
(Score: 4, Insightful) by frojack on Thursday September 14 2017, @06:41PM (1 child)
We should probably look for intelligent life on places colder or hotter than anyplace on earth.
That way we can talk to them someday, but they won't be interested in moving in with us any time soon.
With a great deal of expensive and dangerous machinery we have learned how to stay under the sea or in space for short periods of time, up to a year.
But that doesn't mean we are ready to go to Enceladus and move in with them any time soon. Which is good for them, because we would probably just stink up the place.
No, you are mistaken. I've always had this sig.
(Score: 2) by GreatAuntAnesthesia on Friday September 15 2017, @10:34AM
Meh, just terraform it. Enceladus is only about 500km across. here's how it goes:
1 - Build a giant "Belt" around Enceladus, along the boundary between the "Saturn " and "dark" sides of the tidally-locked moon. This Belt is in effect a dam. It needs to be big, reaching all the way from the bottom of the sea to well above the ice. It will be kilometres high and kilometres wide. Think "The Wall" from Westeros but bigger, and made of something less melty than ice. Enceladus' (very) low gravity will help you here. Some "shelving" around the dam might be useful too.
2 - Now build Towers at regular intervals all over the entire surface, again founded at the bottom of the sea (or from the top of the dam). The towers are built to a height of a few kilometers above the surface of the ice.
3 - At this point (depending on your chemical analysis of the oceans & ice) you might want to dump some extra material on the world- probably nitrogen-or maybe oxygen-rich fragments from Saturn's rings.
4 - Put glass panels between the tops of the towers, effectively sealing the entire world in a big glass bubble. Don't forget to put airlocks / docking facilities in somewhere! (Best way to do this would be to build walls rather than overhead panels between some towers, creating "dimples" in the surface of the bubble that go right the way down to ground level)
5 - Use giant mirrors to vastly increase the sunlight reaching Enceladus, and wait for the ice to melt. As it melts, gasses should be released, forming an atmosphere. Getting the mirrors to orbit correctly within the Saturn system would be a challenge. Might be easier to simply run them on rails across the surface of the bubble, moving against Ence's rotation to create a convenient(ish) 33 hour day/night cycle. You'd also get to enjoy a spectacular eclipse every day!
6 - Tweak atmosphere as necessary, with further import / export of elements from / to the ring system and / or mining the upper layers of Saturn's atmosphere.
7 - Tidal forces will cause the sea to regularly slosh in humongous waves from one side of the world to the other. Remember that giant dam you built? Cheap energy!
8 - Introduce terrestrial sea-life, with particular emphasis on the tastier varieties. Build houses, farms, holiday resorts and surf schools on top of the dam. If there was any native Enceladean life (and it somehow survived the terraforming), it now has nice views of the sky as well as access to fast food, reality TV and digital watches.
(Score: 1, Interesting) by Anonymous Coward on Thursday September 14 2017, @06:54PM
to mars, thank the progenitors they parked the atmosphere in Saturn's orbit
http://www.enterprisemission.com/moon4.htm [enterprisemission.com]
(Score: 3, Interesting) by PiMuNu on Thursday September 14 2017, @07:22PM (3 children)
It would be interesting if we could imagine life forms that do not use photosynthesis as a source of energy, but rather use tidal gravitational forces to harvest energy. I wonder what such a life form would be like? Long? Would it be life?
(Score: 1) by ants_in_pants on Thursday September 14 2017, @07:58PM
We already know of earthly ecosystems that are completely isolated from the sun. They're pretty interesting, often harvesting energy from volcanic processes.
-Love, ants_in_pants
(Score: 2, Informative) by fustakrakich on Friday September 15 2017, @01:26AM (1 child)
You don't have to imagine anything. We've already been there [oceana.org]
La politica e i criminali sono la stessa cosa..
(Score: 2) by PiMuNu on Friday September 15 2017, @04:11PM
Fair point - I was imagining directly harvesting via gravitational tidal forces; which would mean a completely different biology (not necessarily carbon-based, for example)