APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)
Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)
Daphnis, bump this up to high magnification, very instructive
https://saturn.jpl.nasa.gov/resources/7589/
"You can also see the vertical waves caused by the moon’s feeble pull. Each wave corresponds to one up-and-down bob of the moon relative to the rings. Eventually, tides from Saturn pull the particles back down, but that takes a while, and the ripples extend for a long way around the ring."
http://www.slate.com/blogs/bad_astronom ... rings.html
"What causes those ripples? The orbit of Daphnis is not a perfect circle, but instead is very slightly elliptical. That means it’s sometimes closer to the inner edge of the Keeler gap, and sometimes closer to the outer one. The change is small, only about nine km, but that’s enough. When it’s closer to one edge it pulls on the ring particles a bit harder, creating the wave.
But there’s more to it. The orbit of Daphnis is also tipped a bit to the ring plane, a mere 0.0036° from being exactly aligned. That means it bobs up and down out of the ring plane by about 17 km. When it does it drags the ring particles at the gap edges as well. Those waves you see in the image go in and out of the gap, but also up and down by a kilometer or so."
https://saturn.jpl.nasa.gov/resources/7589/
"You can also see the vertical waves caused by the moon’s feeble pull. Each wave corresponds to one up-and-down bob of the moon relative to the rings. Eventually, tides from Saturn pull the particles back down, but that takes a while, and the ripples extend for a long way around the ring."
http://www.slate.com/blogs/bad_astronom ... rings.html
"What causes those ripples? The orbit of Daphnis is not a perfect circle, but instead is very slightly elliptical. That means it’s sometimes closer to the inner edge of the Keeler gap, and sometimes closer to the outer one. The change is small, only about nine km, but that’s enough. When it’s closer to one edge it pulls on the ring particles a bit harder, creating the wave.
But there’s more to it. The orbit of Daphnis is also tipped a bit to the ring plane, a mere 0.0036° from being exactly aligned. That means it bobs up and down out of the ring plane by about 17 km. When it does it drags the ring particles at the gap edges as well. Those waves you see in the image go in and out of the gap, but also up and down by a kilometer or so."
- Astronymus
- Science Officer
- Posts: 151
- Joined: Wed Nov 10, 2010 10:26 pm
- AKA: Astro
- Location: Northern Alps
Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)
This moon is the weirdest thing.
»Only a dead Earth is a good Earth.«
Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)
Its brim appears to indicate it does not tumble.Astronymus wrote:This moon is the weirdest thing.
Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)
that's not Pan. It's Kyle from South Park!
Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)
My guess too... like Enceladus ejecting the Ice in the first place... only a matter of time a moon would, or at least MIGHT, pick up a good deal... it is like a planet, clearing out its orbit, it gathers debris. Maybe that is WHY it is the Encke Gap???? It has cleared much of its orbit.Ray-Optics wrote:Since Pan orbits in the Encke gap along with an irregular ringlet, a hypothesis for the hat brim occurs to me: It is picking up "snow" from this ringlet along its "equator" of spin. Pan's gravity must be very low, so ring snow could pile high. An overall snow layer may also account for the relatively young-looking surface.
:---[===] *
- neufer
- Vacationer at Tralfamadore
- Posts: 18805
- Joined: Mon Jan 21, 2008 1:57 pm
- Location: Alexandria, Virginia
Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)
Art Neuendorffer
Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)
neufer wrote:.
You’ve met Saturn’s ravioli-shaped moon, Pan.
![Chomp! :chomp:](./images/smilies/chomp.gif)
Ann
Color Commentator
- JohnD
- Tea Time, Guv! Cheerio!
- Posts: 1586
- Joined: Wed Feb 16, 2005 2:11 pm
- Location: Lancaster, England
Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)
Art's erudition and polytemporalistic tendency (no doubt the result of residence on Tralfamadore) has led him astray.
My reference was not to Bo-peep (Fool, King Lear, Act 1, Scene 4, Page 8) but to Jeremiah 50:6 (qv)
John
My reference was not to Bo-peep (Fool, King Lear, Act 1, Scene 4, Page 8) but to Jeremiah 50:6 (qv)
John
-
- Don't bring me down
- Posts: 2524
- Joined: Thu Aug 02, 2012 11:24 am
- AKA: Bruce
- Location: East Idaho
Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)
Very nice John. I had to look it up. It fits.JohnD wrote:Art's erudition and polytemporalistic tendency (no doubt the result of residence on Tralfamadore) has led him astray.
My reference was not to Bo-peep (Fool, King Lear, Act 1, Scene 4, Page 8) but to Jeremiah 50:6 (qv)
John
Bruce
Just as zero is not equal to infinity, everything coming from nothing is illogical.
- neufer
- Vacationer at Tralfamadore
- Posts: 18805
- Joined: Mon Jan 21, 2008 1:57 pm
- Location: Alexandria, Virginia
Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)
Click to play embedded YouTube video.
BDanielMayfield wrote:Very nice John. I had to look it up. It fits.JohnD wrote:
Art's erudition and polytemporalistic tendency (no doubt the result of residence on Tralfamadore) has led him astray.
My reference was not to Bo-peep (Fool, King Lear, Act 1, Scene 4, Page 8) but to Jeremiah 50:6 (qv)
Art Neuendorffer
Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)
Fascinating. Do we know if Pan or Atlas spin ? On an axis perpendicular to the ring plane presumably? perhaps their little equatorial sand dune is being manicured by saturns gravity as they rotate, sort of scouring loosely attracted grains on the moonlet into such a center ridge??
- neufer
- Vacationer at Tralfamadore
- Posts: 18805
- Joined: Mon Jan 21, 2008 1:57 pm
- Location: Alexandria, Virginia
Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)
As in the case of almost all moons they are tidally locked.NESLON wrote:
Do we know if Pan or Atlas spin ?
If you are a moon and your planet subtends an angle of 2º or more
(as in the case of the Moon & Earth) then you are tidally locked.
Art Neuendorffer
- Chris Peterson
- Abominable Snowman
- Posts: 18489
- Joined: Wed Jan 31, 2007 11:13 pm
- Location: Guffey, Colorado, USA
- Contact:
Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)
So to answer the question, yes, both moons spin.neufer wrote:As in the case of almost all moons they are tidally locked.NESLON wrote: Do we know if Pan or Atlas spin ?
Assuming, of course, they've had ample time to become locked. AFAIK that applies to all the satellites we know of that meet your rule, but if not, we could assume they represented either recent captures or bodies disrupted by recent collisions or near collisions.If you are a moon and your planet subtends an angle of 2º or more
(as in the case of the Moon & Earth) then you are tidally locked.
Chris
*****************************************
Chris L Peterson
Cloudbait Observatory
https://www.cloudbait.com
*****************************************
Chris L Peterson
Cloudbait Observatory
https://www.cloudbait.com
- neufer
- Vacationer at Tralfamadore
- Posts: 18805
- Joined: Mon Jan 21, 2008 1:57 pm
- Location: Alexandria, Virginia
Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)
Just not in relationship to their immediate surrounds.Chris Peterson wrote:So to answer the question, yes, both moons spin.neufer wrote:As in the case of almost all moons they are tidally locked.NESLON wrote:
Do we know if Pan or Atlas spin ?
(Although Coriolis forces still apply.)
Art Neuendorffer
- Chris Peterson
- Abominable Snowman
- Posts: 18489
- Joined: Wed Jan 31, 2007 11:13 pm
- Location: Guffey, Colorado, USA
- Contact:
Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)
That seems like a confusing way to put it. I'd just say that their rotation period and orbital period are the same. Their "day" and "year" are the same length.neufer wrote:Just not in relationship to their immediate surrounds.Chris Peterson wrote:So to answer the question, yes, both moons spin.neufer wrote: As in the case of almost all moons they are tidally locked.
Chris
*****************************************
Chris L Peterson
Cloudbait Observatory
https://www.cloudbait.com
*****************************************
Chris L Peterson
Cloudbait Observatory
https://www.cloudbait.com
Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)
ah so they are tidally locked. they don't spin in the way i was imagining, in that these moons will always have a particular side facing Saturn.
- geckzilla
- Ocular Digitator
- Posts: 9180
- Joined: Wed Sep 12, 2007 12:42 pm
- Location: Modesto, CA
- Contact:
Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)
Would the Coriolis effect still cause horizontal banding for clouded planets tidally locked with a parent star? This is one of those things that bothers me a lot. I wonder if the heat gradient would cause some unusual cloud patterns that would be more apparent than what the Coriolis effect would cause—for both gaseous and terrestrial planet types.
Just call me "geck" because "zilla" is like a last name.
- JohnD
- Tea Time, Guv! Cheerio!
- Posts: 1586
- Joined: Wed Feb 16, 2005 2:11 pm
- Location: Lancaster, England
Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)
As Pan is tidally locked, it will also have the same radial relationship to its adjacent rings. So if the ridge is the result of ice deposited on its equator as it draws particles from the adjacent rings, why is it all around? Either end, or where the moon is nearest to the rings might be more expected.
Or would particles spiral down onto the surface, to land and augment the ridge?
John
Or would particles spiral down onto the surface, to land and augment the ridge?
John
- neufer
- Vacationer at Tralfamadore
- Posts: 18805
- Joined: Mon Jan 21, 2008 1:57 pm
- Location: Alexandria, Virginia
Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)
Venus is virtually tidally locked and its cloud structure defies all common sense.geckzilla wrote:
Would the Coriolis effect still cause horizontal banding for clouded planets tidally locked with a parent star? This is one of those things that bothers me a lot. I wonder if the heat gradient would cause some unusual cloud patterns that would be more apparent than what the Coriolis effect would cause—for both gaseous and terrestrial planet types.
![Arrow :arrow:](./images/smilies/icon_arrow.gif)
revealed by ultraviolet observations from Pioneer Venus Orbiter.
I, for one, would be extremely hesitant to suggest what the cloud structure on a rapidly rotating tidally locked planet might look like (if different from this example).
Art Neuendorffer
- neufer
- Vacationer at Tralfamadore
- Posts: 18805
- Joined: Mon Jan 21, 2008 1:57 pm
- Location: Alexandria, Virginia
Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)
The only active accretion of ring material currently taking place is on Atlas's neighbor Prometheus which collides with the F ring every 15 hours knocking out particles which then go into some sort of orbit around Prometheus eventually landing in a ridge ring with a prominent peak on the opposite side of Prometheus from the F ring.JohnD wrote:
As Pan is tidally locked, it will also have the same radial relationship to its adjacent rings. So if the ridge is the result of ice deposited on its equator as it draws particles from the adjacent rings, why is it all around? Either end, or where the moon is nearest to the rings might be more expected. Or would particles spiral down onto the surface, to land and augment the ridge?
Art Neuendorffer