Saturn's Moon Titan

[Randy]

Saturn's moon Titan is rapidly migrating away from the planet.
https://www.cnn.com/2020/06/10/world/titan-saturn-rapid-drift-scn/index.html

[Ecurb Noselrub]

All children eventually want to break free of their parents. Titan just feels like he has a ring around his neck, like he was caught in his mother's orbit. He wants to experience the universe on his own, not as a slave to his mom's gravitational pull. She is a bit of a show-off, but she has a very powerful pull on her children. Personally, I think she is full of noxious gas. It I were Titan, I'd move away, too.

[Recusant]

Cool. Sounds like the scientist who first proposed the idea is saying that it has implications for celestial mechanics in general.

[Recusant]

New analysis indicates that Titan isn't harboring an ocean of liquid water under its icy shell, but rather a sort of slush with pockets of liquid water. 

"What scientists found inside Titan was not what anyone expected" | ScienceDaily

The six infrared images of Titan above were created by compiling data collected over the course of the Cassini mission. They depict how the surface of Titan looks beneath the foggy atmosphere, highlighting the variable surface of the moon. Credit: NASA

A new examination of spacecraft data collected more than ten years ago suggests that Saturn's largest moon, Titan, probably does not contain a massive ocean beneath its frozen surface, as scientists once believed. Instead, moving downward through Titan's icy shell would likely reveal additional layers of ice that gradually transition into slushy pathways and isolated pockets of liquid water closer to the moon's rocky interior.

Earlier interpretations of data from NASA's Cassini mission to Saturn led scientists to propose a deep ocean of liquid water hidden beneath Titan's ice. When researchers tested that idea using computer models, however, the results did not align with the physical characteristics seen in the data. A closer reanalysis produced new -- slushier -- conclusions. These results may prompt scientists to revisit assumptions about other icy worlds and refine how they search for life on Titan.

"Instead of an open ocean like we have here on Earth, we're probably looking at something more like Arctic sea ice or aquifers, which has implications for what type of life we might find, but also the availability of nutrients, energy and so on," said Baptiste Journaux, a University of Washington assistant professor of Earth and space sciences.

[Continues . . .]

The paper is open access:

"Titan's strong tidal dissipation precludes a subsurface ocean" | Nature

Abstract:

The Cassini mission provided unprecedented insights into Saturn's largest moon, Titan, from its atmosphere to the deep interior. The moon's large measured response to the tides exerted by Saturn was interpreted as evidence of the existence of a subsurface ocean. This response, twice the value predicted in pre-Cassini studies, has escaped complete explanation.

Here we show that the signature of tidal dissipation in Titan's gravity field is not consistent with the presence of an ocean. Our results arise from the detection of this signature through a reanalysis of the radiometric data acquired by Cassini with improved techniques. We found that substantial energy is being dissipated in the interior (approximately 3–4 TW, corresponding to a tidal quality factor Q ≈ 5), consistent with recent studies of Titan's rotational state.

Because the presence of a liquid layer reduces the tidal dissipation generated below it, these new measurements preclude the existence of a subsurface ocean on Titan and are explained by a model in which dissipation is concentrated in a high-pressure ice layer close to its melting point. This model also reproduces Titan's observed rotational state and static gravity field self-consistently, reconciling all available geophysical measurements.

Efficient ice shell convection can prevent widespread melting and ocean formation, but a slushy high-pressure ice layer is consistent with expectations, indicating that it probably hosts liquid water pockets. The forthcoming Dragonfly mission to Titan will provide a further test of whether a subsurface ocean exists.