Explanation: Many details of Saturn appear clearly in infrared light. Bands of clouds show great structure, including long stretching storms. Also quite striking in infrared is the unusual hexagonal cloud pattern surrounding Saturn's North Pole. Each side of the dark hexagon spans roughly the width of our Earth. The hexagon's existence was not predicted, and its origin and likely stability remains a topic of research. Saturn's famous rings circle the planet and cast shadows below the equator. The featured image was taken by the robotic Cassini spacecraft in 2014 in several infrared colors -- but only processed recently. In September, Cassini's mission will be brought to a dramatic conclusion as the spacecraft will be directed to dive into ringed giant.
Re: APOD: Saturn in Infrared from Cassini (2017 Apr 03)
Posted: Mon Apr 03, 2017 5:28 am
by Chris Peterson
The term "infrared" gets thrown around a lot, and covers a wide wavelength range. In the case of Cassini's cameras, the longest wavelength is 1.1 microns, which is not far outside the visible range. It is near IR. As such we are not seeing IR emitted by heat sources on Saturn (which would require a camera sensitive to tens of microns or longer), but simply reflected IR from the Sun.
Re: APOD: Saturn in Infrared from Cassini (2017 Apr 03)
Posted: Mon Apr 03, 2017 5:31 am
by somebodyshort
If you boil water at certain depths in a pan you get the same hexagonal patern
Re: APOD: Saturn in Infrared from Cassini (2017 Apr 03)
Posted: Mon Apr 03, 2017 7:20 am
by Boomer12k
I suppose it "could" be a heat difference... but my first thought is it is a Pressure difference. Maybe the rotation of Saturn. A pressure trying to "spread out", but is contained by a different material and pressure...so it "bunches" into this shape.
Just my UNEDUCATED GUESS.... AND IT TURNS OUT TO BE....WRONG.... Although Rotation has something to do with it...This site talks about a model and how it pretty much gets it right.
Re: APOD: Saturn in Infrared from Cassini (2017 Apr 03)
Posted: Mon Apr 03, 2017 9:09 am
by heehaw
I remain irritated that we are not ending Cassini by having it very slowly approach a ring to get a close-up showing ring thickness and composition. Perhaps it was dynamically not possible. I vaguely remember some remarks somewhere about "contaminating" a ring? Seemed silly to me. Oh, the solar system will be a lonelier place without us having an eye on what's up at Saturn!
Re: APOD: Saturn in Infrared from Cassini (2017 Apr 03)
Posted: Mon Apr 03, 2017 12:02 pm
by De58te
heehaw wrote:I remain irritated that we are not ending Cassini by having it very slowly approach a ring to get a close-up showing ring thickness and composition. Perhaps it was dynamically not possible. I vaguely remember some remarks somewhere about "contaminating" a ring? Seemed silly to me. Oh, the solar system will be a lonelier place without us having an eye on what's up at Saturn!
It was too risky before. The rings are made out of millions of frozen particles. They look like a flat ring, but there is no way of knowing if there would be a out of line straggler that Cassini could collide with. However you can have your wish. Following April 22nd flyby of Titan, Cassini will begin its spiral into Saturn. There will be 22 close flybys of the Inner ring plane. First one on April 26. NASA plans close up studies of the rings.
Re: APOD: Saturn in Infrared from Cassini (2017 Apr 03)
Posted: Mon Apr 03, 2017 12:38 pm
by neufer
somebodyshort wrote:
If you boil water at certain depths in a pan you get the same hexagonal patern
Those are non-rotating Rayleigh–Bénard convection cells with warm centers.
https://en.wikipedia.org/wiki/Rayleigh%E2%80%93B%C3%A9nard_convection wrote:
<<Rayleigh–Bénard convection is a type of natural convection, occurring in a plane horizontal layer of fluid heated from below, in which the fluid develops a regular pattern of convection cells known as Bénard cells. Rayleigh–Bénard convection is one of the most commonly studied convection phenomena because of its analytical and experimental accessibility. The convection patterns are the most carefully examined example of self-organizing nonlinear systems. Buoyancy, and hence gravity, is responsible for the appearance of convection cells. The initial movement is the upwelling of lesser density fluid from the heated bottom layer. This upwelling spontaneously organizes into a regular pattern of cells.>>
Todays APOD showsrotating Rossby waves around a cold center.
Our slowly rotating Earth produces Rossby waves that are less stable than on rapidly spinning Saturn:
[img3="Meanders of the northern hemisphere's jet stream developing (a, b)
and finally detaching a "drop" of cold air (c).
Orange: warmer air; pink: jet stream; blue: colder air."]https://upload.wikimedia.org/wikipedia/ ... re.svg.png[/img3]
<<Atmospheric Rossby waves result from the conservation of potential vorticity and are influenced by the Coriolis force and pressure gradient. A fluid, on the Earth, that moves toward the pole will deviate toward the east; a fluid moving toward the equator will deviate toward the west (true in either hemisphere). The deviations are caused by the Coriolis force and conservation of potential vorticity which leads to changes of relative vorticity. This is analogous to conservation of angular momentum in mechanics. In planetary atmospheres, including Earth, Rossby waves are due to the variation in the Coriolis effect with latitude. Carl-Gustaf Arvid Rossby first identified such waves in the Earth's atmosphere in 1939 and went on to explain their motion.>>
Re: APOD: Saturn in Infrared from Cassini (2017 Apr 03)
Posted: Mon Apr 03, 2017 11:49 pm
by cboswellinaz
A woodworking tool I have, http://www.rockler.com/3-in-1-hand-countersink, is used to make depressions to accept screws with tapered heads. When I work it into a hole, it leaves an obvious 6-sided depression, even though the tool has 5 blades. I've always puzzled over this. Any relevance here?
Re: APOD: Saturn in Infrared from Cassini (2017 Apr 03)
Posted: Tue Apr 04, 2017 2:02 am
by BDanielMayfield
cboswellinaz wrote:A woodworking tool I have, http://www.rockler.com/3-in-1-hand-countersink, is used to make depressions to accept screws with tapered heads. When I work it into a hole, it leaves an obvious 6-sided depression, even though the tool has 5 blades. I've always puzzled over this. Any relevance here?
Vertical harmonic vibration of your drill press, perhaps? I see now that your using a hand tool. Never mind.
Re: APOD: Saturn in Infrared from Cassini (2017 Apr 03)
Posted: Tue Apr 04, 2017 2:58 am
by neufer
Click to play embedded YouTube video.
cboswellinaz wrote:
A woodworking tool I have, http://www.rockler.com/3-in-1-hand-countersink, is used to make depressions to accept screws with tapered heads. When I work it into a hole, it leaves an obvious 6-sided depression, even though the tool has 5 blades. I've always puzzled over this. Any relevance here?
Any relevance here?
Re: APOD: Saturn in Infrared from Cassini (2017 Apr 03)
Posted: Wed Apr 05, 2017 4:48 pm
by Ironwood
Just wanted to discuss the elephant in the room that no one has mentioned. What is that wild arc feature that looks as it it is exiting the rings on the bottom right? It looks somewhat like SOHO's view of a comet spiraling into the sun. Very prominent and very bright.
Re: APOD: Saturn in Infrared from Cassini (2017 Apr 03)
Posted: Wed Apr 05, 2017 4:59 pm
by Chris Peterson
Ironwood wrote:Just wanted to discuss the elephant in the room that no one has mentioned. What is that wild arc feature that looks as it it is exiting the rings on the bottom right? It looks somewhat like SOHO's view of a comet spiraling into the sun. Very prominent and very bright.
A band structure in Saturn's atmosphere, seen through the rings.
Re: APOD: Saturn in Infrared from Cassini (2017 Apr 03)
Posted: Wed Apr 05, 2017 7:44 pm
by BDanielMayfield
Chris Peterson wrote:
Ironwood wrote:Just wanted to discuss the elephant in the room that no one has mentioned. What is that wild arc feature that looks as it it is exiting the rings on the bottom right? It looks somewhat like SOHO's view of a comet spiraling into the sun. Very prominent and very bright.
A band structure in Saturn's atmosphere, seen through the rings.
And/or, the thin sliver of Saturn's Sunlit atmosphere beneath the shadow cast onto Saturn by its rings.
Bruce
Re: APOD: Saturn in Infrared from Cassini (2017 Apr 03)
Posted: Wed Apr 05, 2017 9:53 pm
by Chris Peterson
BDanielMayfield wrote:
Chris Peterson wrote:
Ironwood wrote:Just wanted to discuss the elephant in the room that no one has mentioned. What is that wild arc feature that looks as it it is exiting the rings on the bottom right? It looks somewhat like SOHO's view of a comet spiraling into the sun. Very prominent and very bright.
A band structure in Saturn's atmosphere, seen through the rings.
And/or, the thin sliver of Saturn's Sunlit atmosphere beneath the shadow cast onto Saturn by its rings.
That's what I thought at first, but it looks like we can see an unlit southern limb below the lit region.
Re: APOD: Saturn in Infrared from Cassini (2017 Apr 03)
Posted: Wed Apr 05, 2017 11:45 pm
by BDanielMayfield
Chris Peterson wrote:
BDanielMayfield wrote:
Chris Peterson wrote:
A band structure in Saturn's atmosphere, seen through the rings.
And/or, the thin sliver of Saturn's Sunlit atmosphere beneath the shadow cast onto Saturn by its rings.
That's what I thought at first, but it looks like we can see an unlit southern limb below the lit region.
Oh yes, I see that "unlit" part of Saturn now that you point it out. It is quite dim compared to the bright band just below the ring shadow. To me it seems that this area is lit, but just barely as with twilight near the terminator.
Saturn in Infrared from Cassini
I see now that your using a hand tool. Never mind.
Any relevance here?
