by Ann » Sat Aug 26, 2023 4:33 am
johnnydeep wrote: ↑Fri Aug 25, 2023 10:37 pm
Roy wrote: ↑Fri Aug 25, 2023 9:43 pm
johnnydeep wrote: ↑Fri Aug 25, 2023 6:15 pm
Therefore oblate? What facts of those you listed would imply that?
Very large planet, less dense than water, (hydrogen & helium) rotating in such high spin rate, the centrifugal forces must be very high. Those facts.
I see, that makes sense! Thanks.
Another thing: the Wikipedia article doesn’t make sense to me. How can measuring the diameter of the rings lead to a surmise that the core is less dense? All the descriptions of Saturn’s core are conjecture. No one knows if hydrogen ice is possible, not to mention helium ice, both under enormous pressure at unknown temperatures.
Yeah, that didn't make much sense to me either, but the referenced paper presumably explains it. But I only have access to the abstract:
https://www.nature.com/articles/s41550-021-01448-3 wrote:Abstract
The best constraints on the internal structures of giant planets have historically originated from measurements of their gravity fields1,2,3. These data are inherently mostly sensitive to a planet’s outer regions, stymieing efforts to measure the mass and compactness of the cores of Jupiter2,4,5 and Saturn6,7. However, studies of Saturn’s rings have detected waves driven by pulsation modes within the planet8,9,10,11, offering independent seismic probes of Saturn’s interior12,13,14. The observations reveal gravity-mode pulsations, which indicate that part of Saturn’s deep interior is stable against convection13. Here, we compare structural models with gravity and seismic measurements from Cassini to show that the data can only be explained by a diffuse, stably stratified core–envelope transition region in Saturn extending to approximately 60% of the planet’s radius and containing approximately 17 Earth masses of ice and rock. This gradual distribution of heavy elements constrains mixing processes at work in Saturn, and it may reflect the planet’s primordial structure and accretion history.
The information in the abstract is the kind of information that I expect I will be able to digest. I know that seismic waves are used to probe the interior of the Earth, and also the interior of the Sun, if I am not mistaken. The abstract told us (or so I think) that the rings of Saturn function as an "extension" of the "medium" through which seismic waves can pass in Saturn, and the waves in the rings can therefore be used to constrain the nature of the interior of Saturn. In the abstract, it is said that part of Saturn's deep interior is stable against convection (= mixing), i.e., the deep interior of Saturn appears to be a solid core.
Apparently convection processes are more and more constrained closer and closer to the core. Clearly there is more and more ice and rock mixed with gases the deeper one gets into the interior of Saturn, which is what is meant by a diffuse core. But the inner regions are also stably stratified.
I loved the suggestion that the distribution of heavy elements of Saturn may reflect the planet's primordial structure and accretion history.
Ann
[quote=johnnydeep post_id=333250 time=1693003079 user_id=132061]
[quote=Roy post_id=333248 time=1692999785]
[quote=johnnydeep post_id=333238 time=1692987332 user_id=132061]
[i]Therefore [/i]oblate? What facts of those you listed would imply that?
[/quote]
Very large planet, less dense than water, (hydrogen & helium) rotating in such high spin rate, the centrifugal forces must be very high. Those facts.
[/quote]
I see, that makes sense! Thanks.
[quote]
Another thing: the Wikipedia article doesn’t make sense to me. How can measuring the diameter of the rings lead to a surmise that the core is less dense? All the descriptions of Saturn’s core are conjecture. No one knows if hydrogen ice is possible, not to mention helium ice, both under enormous pressure at unknown temperatures.
[/quote]
Yeah, that didn't make much sense to me either, but the referenced paper presumably explains it. But I only have access to the abstract:
[quote=https://www.nature.com/articles/s41550-021-01448-3][size=150]Abstract[/size]
The best constraints on the internal structures of giant planets have historically originated from measurements of their gravity fields1,2,3. These data are inherently mostly sensitive to a planet’s outer regions, stymieing efforts to measure the mass and compactness of the cores of Jupiter2,4,5 and Saturn6,7. However, studies of Saturn’s rings have detected waves driven by pulsation modes within the planet8,9,10,11, offering independent seismic probes of Saturn’s interior12,13,14. The observations reveal gravity-mode pulsations, which indicate that part of Saturn’s deep interior is stable against convection13. Here, we compare structural models with gravity and seismic measurements from Cassini to show that the data can only be explained by a diffuse, stably stratified core–envelope transition region in Saturn extending to approximately 60% of the planet’s radius and containing approximately 17 Earth masses of ice and rock. This gradual distribution of heavy elements constrains mixing processes at work in Saturn, and it may reflect the planet’s primordial structure and accretion history.[/quote]
[/quote]
The information in the abstract is the kind of information that I expect I will be able to digest. I know that seismic waves are used to probe the interior of the Earth, and also the interior of the Sun, if I am not mistaken. The abstract told us (or so I think) that the rings of Saturn function as an "extension" of the "medium" through which seismic waves can pass in Saturn, and the waves in the rings can therefore be used to constrain the nature of the interior of Saturn. In the abstract, it is said that part of Saturn's deep interior is stable against convection (= mixing), i.e., the deep interior of Saturn appears to be a solid core.
Apparently convection processes are more and more constrained closer and closer to the core. Clearly there is more and more ice and rock mixed with gases the deeper one gets into the interior of Saturn, which is what is meant by a diffuse core. But the inner regions are also stably stratified.
I loved the suggestion that the distribution of heavy elements of Saturn may reflect the planet's primordial structure and accretion history.
[img3="Primordial pre-ring and gas Saturn? The illustration actually shows the largest rocky planet found so far, BD+20594b. Credit: JPL/Caltech."]https://scx2.b-cdn.net/gfx/news/2016/largestrocky.jpg[/img3]
Ann