APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)

Comments and questions about the APOD on the main view screen.
douglas

Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)

Postby douglas » Mon Mar 13, 2017 7:18 pm

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."

User avatar
Astronymus
Ensign
Posts: 51
Joined: Wed Nov 10, 2010 10:26 pm
AKA: Astro
Location: Astroplanet

Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)

Postby Astronymus » Mon Mar 13, 2017 9:36 pm

This moon is the weirdest thing.

douglas

Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)

Postby douglas » Mon Mar 13, 2017 11:21 pm

Astronymus wrote:This moon is the weirdest thing.


Its brim appears to indicate it does not tumble.

ccnield27@outlook.com

Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)

Postby ccnield27@outlook.com » Mon Mar 13, 2017 11:45 pm

that's not Pan. It's Kyle from South Park!

Boomer12k
:---[===] *
Posts: 1947
Joined: Sun Apr 22, 2007 12:07 am

Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)

Postby Boomer12k » Tue Mar 14, 2017 12:37 am

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.


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.

:---[===] *

User avatar
neufer
Vacationer at Tralfamadore
Posts: 13886
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)

Postby neufer » Thu Mar 16, 2017 9:53 pm

.
You’ve met Saturn’s ravioli-shaped moon, Pan.
Now learn how it was discovered.
Art Neuendorffer

User avatar
Ann
4725 Å
Posts: 8180
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)

Postby Ann » Thu Mar 16, 2017 10:58 pm

neufer wrote:.
You’ve met Saturn’s ravioli-shaped moon, Pan.

:chomp:

Ann
Color Commentator

User avatar
JohnD
Tea Time, Guv! Cheerio!
Posts: 932
Joined: Wed Feb 16, 2005 2:11 pm
Location: Lancaster, England

Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)

Postby JohnD » Fri Mar 17, 2017 9:12 am

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

BDanielMayfield
Don't bring me down
Posts: 1330
Joined: Thu Aug 02, 2012 11:24 am
AKA: Bruce
Location: South Texas

Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)

Postby BDanielMayfield » Fri Mar 17, 2017 11:41 am

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


Very nice John. I had to look it up. It fits.

Bruce
"Happy are the peaceable ... "

User avatar
neufer
Vacationer at Tralfamadore
Posts: 13886
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)

Postby neufer » Fri Mar 17, 2017 1:01 pm

Click to play embedded YouTube video.
BDanielMayfield wrote:
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)

Very nice John. I had to look it up. It fits.
Art Neuendorffer

NESLON

Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)

Postby NESLON » Thu Mar 30, 2017 8:29 am

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??

User avatar
neufer
Vacationer at Tralfamadore
Posts: 13886
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)

Postby neufer » Thu Mar 30, 2017 12:05 pm

NESLON wrote:
Do we know if Pan or Atlas spin ?

As in the case of almost all moons they are tidally locked.

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

User avatar
Chris Peterson
Abominable Snowman
Posts: 12934
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)

Postby Chris Peterson » Thu Mar 30, 2017 2:13 pm

neufer wrote:
NESLON wrote:Do we know if Pan or Atlas spin ?

As in the case of almost all moons they are tidally locked.

So to answer the question, yes, both moons 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.

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.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

User avatar
neufer
Vacationer at Tralfamadore
Posts: 13886
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)

Postby neufer » Thu Mar 30, 2017 3:30 pm

Chris Peterson wrote:
neufer wrote:
NESLON wrote:
Do we know if Pan or Atlas spin ?

As in the case of almost all moons they are tidally locked.

So to answer the question, yes, both moons spin.

Just not in relationship to their immediate surrounds.

(Although Coriolis forces still apply.)
Art Neuendorffer

User avatar
Chris Peterson
Abominable Snowman
Posts: 12934
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)

Postby Chris Peterson » Thu Mar 30, 2017 3:47 pm

neufer wrote:
Chris Peterson wrote:
neufer wrote:As in the case of almost all moons they are tidally locked.

So to answer the question, yes, both moons spin.

Just not in relationship to their immediate surrounds.

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.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

NESLON

Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)

Postby NESLON » Fri Mar 31, 2017 6:18 am

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.

User avatar
geckzilla
Ocular Digitator
Posts: 8495
Joined: Wed Sep 12, 2007 12:42 pm

Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)

Postby geckzilla » Fri Mar 31, 2017 8:19 am

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.

User avatar
JohnD
Tea Time, Guv! Cheerio!
Posts: 932
Joined: Wed Feb 16, 2005 2:11 pm
Location: Lancaster, England

Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)

Postby JohnD » Fri Mar 31, 2017 10:08 am

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

User avatar
neufer
Vacationer at Tralfamadore
Posts: 13886
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)

Postby neufer » Fri Mar 31, 2017 12:33 pm

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.


Venus is virtually tidally locked and its cloud structure defies all common sense.

:arrow: Cloud structure in Venus's atmosphere in 1979,
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

User avatar
neufer
Vacationer at Tralfamadore
Posts: 13886
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Saturn's Moon Pan from Cassini (2017 Mar 13)

Postby neufer » Fri Mar 31, 2017 1:40 pm

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?

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.
Art Neuendorffer


Return to “The Bridge: Discuss an Astronomy Picture of the Day”

Who is online

Users browsing this forum: Bing [Bot], CommonCrawl [Bot] and 2 guests