The Moons of Saturn

[Christopher K.]

Thanks to the active Cassini mission so much more is known about the moons of Saturn. Saturn has fifty-three confirmed moons and, as of this posting, nine provisional moons.

500-kilometer wide Enceladus, discovered in 1789 by William Herschel, has a smooth surface so bright it reflects almost all of the sunlight that hits it. Cassini has uncovered the amazing facts that Enceladus spews icy geysers so high, the water vapor escapes at 400 meters per second. The 4 August APOD is an image from the Cassini team showing plenty of plume activity.

4 August 2014 APOD:
http://apod.nasa.gov/apod/ap140804.html

[Christopher K.]

It was announced in Icarus in July that Titan probably has a salty ocean below its shell of ice; that shell is about 50 kilometers thick on average.

Also see...
http://saturn.jpl.nasa.gov/news/newsrel ... e20140702/

[Christopher K.]

The Cassini spacecraft has helped scientists map the locations of 100 liquid jets erupting on the surface of Enceladus. Two 28 July papers in The Astronomical Journal describe the details of the mapping. Cassini first saw plumes at Enceladus in 2005.

[Christopher K.]

A recently-released video from the Jet Propulsion Laboratory shows plasma waves transmitted from Saturn to Enceladus on 2 September 2017 after they have been compressed from twenty-eight minutes of real time to less than a half-minute. Scientists also decreased the wave frequency by a factor of five. The resulting sounds are eerie.

The video:
https://jpl.jpl.nasa.gov/video/details.php?id=1539

[fred8615]

Data from the Cassini mission keeps fuelling discoveries. The latest discovery is that Saturn’s tiny moon Mimas may have an internal ocean. If it does, the moon joins a growing list of natural satellites in our Solar System that may harbour liquid water under their surfaces.

Worlds with interior oceans are called Interior Water Ocean Worlds (IWOWs). If the new paper announcing this discovery is correct, tiny Mimas will join worlds like Europa, Enceladus, Titan—and maybe Pluto—on the growing list of IWOWs in our Solar System. How did scientists discover that Mimas is a potential IWOW?

It’s all thanks to the Cassini mission to Saturn, a collaboration between NASA, the ESA, and the Italian Space Agency. That mission ended with a plunge into Saturn in 2017, called the Grand Finale. But before it concluded its mission with a purposeful plunge into the gas giant’s atmosphere, the spacecraft’s instruments detected an unusual libration in Mimas’ rotation.

Librations like the one found in Mimas’ rotation are often indicators of a geologically active world with a subsurface ocean.

A new paper published in the journal Icarus explains the findings. Its title is “The case for an ocean-bearing Mimas from tidal heating analysis,” and it’s available online at Science Direct. The authors are Alyssa Rose Rhodena and Matthew E. Walker. Rhodena is an expert in the geophysics of icy satellites at the Southwest Research Institute, and Walker is an Associate Research Scientist at the Planetary Science Institute.

If Mimas is an IWOW, it would be different from others in the Solar System like Europa and Enceladus. Those ocean-bearing moons show geological activity that Mimas lacks. The authors point out that the physical librations Cassini sensed “… can be explained by either a non-hydrostatic core or a global, liquid water ocean beneath a 24–31 km thick ice shell.”

Read more: https://www.universetoday.com/154124/ev ... uid-water/

[Christopher K.]

The Cassini mission is gone but not forgotten. Today’s APOD shows Enceladus illuminated by “Saturnshine”—not counting the far right crescent receiving direct sunlight. The lower left limb of the moon has icy plumes emanating from it.

5 February 2023 APOD:
https://apod.nasa.gov/apod/ap230205.html