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Saturn's ocean moon Enceladus has fresh ice in unexpected place

In these detailed infrared images of Saturn's icy moon Enceladus, reddish areas indicate fresh ice that has been deposited on the surface. (Image credit: NASA/JPL-Caltech/University of Arizona/LPG/CNRS/University of Nantes/Space Science Institute)

Saturn's geyser-spewing moon Enceladus may be even more active than scientists had thought.

Fresh images created using data from NASA's dead Cassini spacecraft show that Enceladus' northern hemisphere was resurfaced with ice relatively recently. This new information adds to the known activity in the southern hemisphere, where Cassini spotted more than 100 geysers blasting icy water into space.

Researchers spotted the northern changes after looking at the heat signature of Enceladus, using reflected sunlight parsed with Cassini's visible and infrared mapping spectrometer instrument, or VIMS. 

Related: Photos of Saturn's ocean moon Enceladus

"Thanks to these infrared eyes [on Cassini], you can go back in time and say that one large region in the northern hemisphere appears also young and was probably active not that long ago, in geologic timelines," Gabriel Tobie, a study co-author and VIMS scientist at the University of Nantes in France, said in a NASA statement

The team combined VIMS data with visible imagery captured by Cassini to create a new, global map of Enceladus in multiple wavelengths of light, both infrared and visible. The map shows that the infrared signals correlate with recent geologic activity on the moon, the researchers said.

For example, heat signatures match up with the "tiger stripe" gashes near Enceladus' south pole. The tiger stripes are the launch pad for the moon's dramatic geysers, which send water and other material from Enceladus' subsurface ocean out into the void.

To the surprise of scientists, however, the new map also shows infrared features in the moon's northern hemisphere. The data suggests that icy resurfacing also happened up north, but how is not yet clear. The changes could have been due to more icy jets, or slower ice movements through cracks in the crust, team members said.

Enceladus is one of the most promising abodes for alien life in the solar system. In addition to the subsurface ocean and geological activity, the moon likely has an energy source that organisms could tap into — chemical reactions perhaps similar to those that sustain life near Earth's deep-sea hydrothermal vents.

There is no future mission planned yet to target Enceladus, although scientists made the pitch for one during a presentation coordinated by the U.S. National Academies of Sciences on March 31. In the meantime, researchers must rely on data collected by older missions. 

Cassini will be a continuing help in providing such information. The mission gathered data about Saturn and its many moons for 13 years before, low on fuel, it was sent on a deliberate suicide plunge into the gas giant's thick atmosphere. Cassini's long-term observations show how the planet and its moons changed over time, providing vital questions for future spacecraft to explore in more detail.

The new study was published online last month in the journal Icarus. The research was led by Rozenn Robidel, a researcher at the laboratory of planetology and geodynamics at France's National Centre for Scientific Research (CNRS).

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  • rod
    FYI, here is a bit from another report on this topic. "New composite images made from NASA's Cassini spacecraft are the most detailed global infrared views ever produced of Saturn's moon Enceladus. And data used to build those images provides strong evidence that the northern hemisphere of the moon has been resurfaced with ice from its interior..."The infrared shows us that the surface of the south pole is young, which is not a surprise because we knew about the jets that blast icy material there," said Gabriel Tobie, VIMS scientist with the University of Nantes in France and co-author of the new research published in Icarus. "Now, thanks to these infrared eyes, you can go back in time and say that one large region in the northern hemisphere appears also young and was probably active not that long ago, in geologic timelines.", ref - https://phys.org/news/2020-09-infrared-eyes-enceladus-hints-fresh.html
    A young surface age is encountered, not expected. Concerning the south pole surface age, there is "A further issue with these hypotheses is that the `tiger stripes' may be short-lived. We show here that impact resurfacing can seal off plumes and mass loss can lead to their compression and closure over ∼1Myr . Since plumes are observed at present, a mechanism by which new plumes can be generated every ∼1Myr and by which such plumes are most likely to form at the south pole is needed.", ref - Repeated Impact-Driven Plume Formation On Enceladus Over Myr Timescales, https://ui.adsabs.harvard.edu/abs/2020arXiv200307866S/abstract
    My observation. Like apparent young age for Saturn's rings, young surface ages are difficult to reconcile with the conventional long age for the solar system, i.e. some 4.5 billion years.
    Reply
  • Torbjorn Larsson
    This is highly interesting since it promotes Enceladus as a globally active ocean world!

    It, and now Venus, place it on the list of a handful worlds where we can expect life has evolved (seeing how fast it started here and how diverse it has been ever since). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6152910/pdf/emss-78644.pdf ]
    Reply
  • Torbjorn Larsson
    rod said:
    Since plumes are observed at present, a mechanism by which new plumes can be generated every ∼1Myr and by which such plumes are most likely to form at the south pole is needed.", ref - Repeated Impact-Driven Plume Formation On Enceladus Over Myr Timescales, https://ui.adsabs.harvard.edu/abs/2020arXiv200307866S/abstract
    ... Like apparent young age for Saturn's rings, young surface ages are difficult to reconcile with the conventional long age for the solar system, i.e. some 4.5 billion years.

    ? All these ages are separate phenomena: age of the solar system, ages of young debris disks and other young satellites, ages of oceans on water worlds.

    The age of the solar system is known to better precision than the age of the local universe, itself a wonder of precision dating 3 times as old, thanks to meteorites. "The oldest inclusions found in meteorites, thought to trace the first solid material to form in the presolar nebula, are 4568.2 million years old, which is one definition of the age of the Solar System." https://en.wikipedia.org/wiki/Formation_and_evolution_of_the_Solar_System#Presolar_nebula ]
    The age of Enceladus may be no more than 100 Myrs https://en.wikipedia.org/wiki/Enceladus#Date_of_formation ]. The suggested formation process is from older moons after an orbital resonance with the Sun https://astronomy.com/news/2016/03/moons-of-saturn-may-be-younger-than-the-dinosaurs ] - but I'm sure there was alternate hypotheses after the orbital models uncovered the age problem.

    The age of Enceladus ocean is an open question as well https://en.wikipedia.org/wiki/Enceladus#Possible_heat_sources ].
    Reply
  • rod
    The assumption in post #4 uses meteorites as a fixed age reference, now dating back to 1956 Clair Patterson studies. This methodology presented keeps the fixed age reference from scientific falsification :) What is presented is circular reasoning in an effort to avoid showing the 1956 age is wrong :)
    Reply