APOD: Fresh Tiger Stripes on Saturn's... (2024 Aug 25)

[APOD Robot]

Fresh Tiger Stripes on Saturn's Enceladus

Explanation: Do underground oceans vent through canyons on Saturn's moon Enceladus? Long features dubbed tiger stripes are known to be spewing ice from the moon's icy interior into space, creating a cloud of fine ice particles over the moon's South Pole and creating Saturn's mysterious E-ring. Evidence for this has come from the robot Cassini spacecraft that orbited Saturn from 2004 to 2017. Pictured here, a high resolution image of Enceladus is shown from a close flyby. The unusual surface features dubbed tiger stripes are visible in false-color blue. Why Enceladus is active remains a mystery, as the neighboring moon Mimas, approximately the same size, appears quite dead. An analysis of ejected ice grains has yielded evidence that complex organic molecules exist inside Enceladus. These large carbon-rich molecules bolster -- but do not prove -- that oceans under Enceladus' surface could contain life.

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[zendae]

The tiger stripes at the bottom look like river deltas, but there is no sea to form them. On Earth, deltas are very rich and biodiverse. These structures on Enceladus seem like interesting places to explore.

[Ann]

The activity of Enceladus is astounding, for such a tiny Moon!

Fresh Tiger Stripes on Saturn's Enceladus. Image Credit: NASA, ESA, JPL, SSI, Cassini Imaging Team

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Enceladus is about the size of Great Britain, and it could fit comfortably inside the Gulf of Mexico:

The size of Enceladus compared with Great Britain. Credit: NASA/JPL/SSI

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The size of Enceladus compared with the Gulf of Mexico and the Moon. Credit: WALTER MYERS / SCIENCE PHOTO LIBRARY

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Enceladus is astoundingly active:

This illustration shows Cassini(?) flying through the plumes of ice and vapor jettisoned from the Tiger stripes of Enceladus. Credit: NASA/JPL-Caltech/Space Science Institute

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Creation of Enceladus' plumes and jets. Credit: ESA; F. Postberg Et Al (2018)

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NASA Science wrote about the picture of Enceladus' interior:

Left: The interior of Saturn’s moon Enceladus. The icy crust is thinner in the polar regions, below which sits an ocean. Water percolating into the porous, rocky core is warmed by contact with rock in the tidally heated interior. The heated water enters the ocean at hydrothermal vents located beneath the poles. Complex organics and rocky particles are carried by the hydrothermal flow. Gas bubbles rising through the ocean collect organic material at their surface and transport them upward to the ice shell.

Center: The oceanic water table lies inside cracks in the south polar ice crust. Bubbles of gas help bring organic material to the ocean surface, where it creates a thin film in the icy vents.

Right: When the bubbles burst at the surface they disperse some of the organics, along with a spray of salty ocean water. Droplets of the dispersed organic material become ice-coated when water vapor freezes on their surface and, along with the frozen spray of salty ocean water, are ejected in the plumes and then detected by Cassini.

Note that the insets at center and right are rotated 180º with respect to the global view at left.

The plumes of Enceladus form a ring around Saturn, the E ring, the outermost ring:

The plumes of Enceladus create the E ring of Saturn. Credit: NASA/JPL/Space Science Institute

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The E ring is blue in color, because the particles making up the E ring are just the right size to scatter blue light from the Sun. Credit: NASA/JPL-Caltech/SSI

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Could there be life inside Enceladus? Well, maybe possibly maybe:

Microbes that don't need sunlight flourish near the bottom of the sea on the Earth. Maybe they exist inside Enceladus, too? Credit: (Getty Images/remotevfx)

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Ann

[JimB]

As Enceladus is spewing out water containing organics, shouldn't those surface features be a sort of mucky brown colour?

[Roger Venable]

One of the very interesting things about Encheladus is the crisp demarkation between the "old" surface that contains lots of craters and the "young" surface that has none. The tiger stripes are all in the young surface, of course. Is the internal ocean covering only the southern part of the moon?

[johnnydeep]

As Enceladus is spewing out water containing organics, shouldn't those surface features be a sort of mucky brown colour?

Like Sagan's "tholins" (from Gk ϴὸλος, muddy; but also ϴoλòς, vault or dome), I suppose. But how and why their color might vary depending on particular composition and environment, I have no idea. See https://www.planetary.org/articles/0722 ... re-tholins

Although informative, the definition given in the Nature article is not particularly easy to repeat when people ask, “what is tholin?” I have been studying tholin for almost a decade and in my experience the most frequently used synonyms for tholin are “gunk”, “brown gunk”, and “complex organic gunk”. Tholin is also often described as a “tar-like” substance. Words like tar, kerogen, bitumen, petroleum, asphalt, etc. all describe substances that are potentially similar to tholin in some ways. However, these materials all result from life; they are “biotic”.

Since 1979, the definition of tholin has expanded and now often includes organic solids produced from irradiation of cosmically abundant ices (rather than gases), and tholin experiments now routinely include other gases like N2, CO2, or CO. So what do scientists mean whey they say tholin? In general, we mean an abiotic complex organic solid that formed by chemistry from energy input into simple, cosmically relevant gases or solids. Shorter still, “abiotic complex organic gunk” works for me. You can see, perhaps, why Sagan and Khare felt the need to make up a word to capture this idea.

[Ann]

As Enceladus is spewing out water containing organics, shouldn't those surface features be a sort of mucky brown colour?

As for the color of Enceladus, this is the best I can do:

Saturn's moon Dione in natural and 'super' color. Credit: Maybe Dr. Paul Schenk

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Enceladus in natural (left) and super' color. Credit: Maybe Dr. Paul Schenk

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https://stereomoons.blogspot.com/2015/0 ... moons.html

In other words, Enceladus appears to be greenish, possibly because of the organics it's spewing out.

Ann

[AVAO]

The plumes of Enceladus create the E ring of Saturn. Credit: NASA/JPL/Space Science Institute

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The E ring is blue in color, because the particles making up the E ring are just the right size to scatter blue light from the Sun. Credit: NASA/JPL-Caltech/SSI

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Ann

ThanX Ann
I like you analysis.

Enhanced structures:

Click to view full size image

Click to view full size image

Just 4 fun: Saturn, Enceladus, Earth & Moon in real dimensions and distances.:

Click to view full size image

biggg:https://live.staticflickr.com/65535/539 ... 4901_o.jpg

Collage Jac Berne (flickr)

Annotated: https://photojournal.jpl.nasa.gov/figur ... 2_fig3.jpg

[Ann]

The plumes of Enceladus create the E ring of Saturn. Credit: NASA/JPL/Space Science Institute

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The E ring is blue in color, because the particles making up the E ring are just the right size to scatter blue light from the Sun. Credit: NASA/JPL-Caltech/SSI

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Ann

ThanX Ann
I like you analysis.

Enhanced structures:

Click to view full size image

Click to view full size image

Just 4 fun: Saturn, Enceladus, Earth & Moon in real dimensions and distances.:

Click to view full size image

biggg:https://live.staticflickr.com/65535/539 ... 4901_o.jpg

Collage Jac Berne (flickr)

Annotated: https://photojournal.jpl.nasa.gov/figur ... 2_fig3.jpg

Thank you so much, as always, for your pictures, Jac! The one where the E ring and its overall structures are seen in blue is particularly lovely, not just for its colors, but of course, also for its colors...

And I very much like the comparison of the sizes of Saturn, Earth, the Moon and Enceladus!

Ann

[Guest]

Has anyone put together a time lapse of the tiger stripes to see how much they’re changing over the decades we’ve been observing them? The angles and resolutions would vary greatly, but I’m betting some software could blend it together.

[Chris Peterson]

Has anyone put together a time lapse of the tiger stripes to see how much they’re changing over the decades we’ve been observing them? The angles and resolutions would vary greatly, but I’m betting some software could blend it together.

We only have a few years of high resolution imagery available, around 2005-2017, and I think most of that is at the beginning and end of that period.