APOD: In, Through, and Beyond Saturn's Rings (2021 Apr 04)

[APOD Robot]

In, Through, and Beyond Saturn's Rings

Explanation: Four moons are visible on the featured image -- can you find them all? First -- and farthest in the background -- is Titan, the largest moon of Saturn and one of the larger moons in the Solar System. The dark feature across the top of this perpetually cloudy world is the north polar hood. The next most obvious moon is bright Dione, visible in the foreground, complete with craters and long ice cliffs. Jutting in from the left are several of Saturn's expansive rings, including Saturn's A ring featuring the dark Encke Gap. On the far right, just outside the rings, is Pandora, a moon only 80-kilometers across that helps shepherd Saturn's F ring. The fourth moon? If you look closely inside Saturn's rings, in the Encke Gap, you will find a speck that is actually Pan. Although one of Saturn's smallest moons at 35-kilometers across, Pan is massive enough to help keep the Encke gap relatively free of ring particles. After more than a decade of exploration and discovery, the Cassini spacecraft ran low on fuel in 2017 and was directed to enter Saturn's atmosphere, where it surely melted.

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[JohnD]

Pandora, clearly elliptical in outline on that photo, but then its brother moon Prometheus is too.
Are these captured asteroids, or agglomerations of ice from the rings?

[VictorBorun]

are elongated minor moons binary mergers at their core?

[orin stepanek]

I'm glad I found Pan before reading about it's location!

[Confused]

I see a small bump in front of Titan to the right of its left side and in the ring. Is that something?

[Avalon]

There appears to be a ghostly echo around Titan, especially visible at the poles. Is it an atmosphere of some sort? What am I seeing?

[neufer]

There appears to be a ghostly echo around Titan, especially visible at the poles. Is it an atmosphere of some sort? What am I seeing?

"The main tholin haze layer lies in the stratosphere at about 100–210 km. In this layer of the atmosphere there is a strong temperature inversion caused by the haze due to a high ratio of shortwave to infrared opacity."

Titan's atmosphere backlit by the Sun, with Saturn's rings behind. An outer haze layer merges at top with the northern polar hood.

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<<Titan's vertical atmospheric structure is similar to Earth. They both have a troposphere, stratosphere, mesosphere, and thermosphere. However, Titan's lower surface gravity creates a more extended atmosphere, with scale heights of 15–50 km in comparison to 5–8 km on Earth. Voyager data, combined with data from Huygens and radiative-convective models provide increased understanding of Titan's atmospheric structure.

Troposphere: This is the layer where a lot of the weather occurs on Titan. Since methane condenses out of Titan's atmosphere at high altitudes, its abundance increases below the tropopause at an altitude of 32 km, leveling off at a value of 4.9% between 8 km and the surface. Methane rain, haze rainout, and varying cloud layers are found in the troposphere.

Stratosphere: The atmospheric composition in the stratosphere is 98.4% nitrogen—the only dense, nitrogen-rich atmosphere in the Solar System aside from Earth's—with the remaining 1.6% composed mostly of methane (1.4%) and hydrogen (0.1–0.2%). The main tholin haze layer lies in the stratosphere at about 100–210 km. In this layer of the atmosphere there is a strong temperature inversion caused by the haze due to a high ratio of shortwave to infrared opacity.

Mesosphere: A detached haze layer is found at about 450–500 km, within the mesosphere. The temperature at this layer is similar to that of the thermosphere because of the cooling of hydrogen cyanide (HCN) lines.

Thermosphere: Particle production begins in the thermosphere. This was concluded after finding and measuring heavy ions and particles. This was also Cassini's closest approach in Titan's atmosphere.

Ionosphere: Titan's ionosphere is also more complex than Earth's, with the main ionosphere at an altitude of 1,200 km but with an additional layer of charged particles at 63 km. This splits Titan's atmosphere to some extent into two separate radio-resonating chambers. The source of natural extremely-low-frequency (ELF) waves on Titan, as detected by Cassini–Huygens, is unclear as there does not appear to be extensive lightning activity.>>

[nam888id]

The picture reminds me of some artist's concept of space travel on Star Trek.

[MarkBour]

The picture reminds me of some artist's concept of space travel on Star Trek.

Yes. Wow, I love this picture. I'm wondering if some genius at NASA planned the shot, in order to get that much going on in one image?
I want to call it a Kubrickian shot.

I see a small bump in front of Titan to the right of its left side and in the ring. Is that something?

Thanks for pointing to that. I see what you're talking about. Could it be another tiny moon? If so, it might be almost as large as Pan.

[JohnD]

MarkBour,
I think what you are seeing (seven o'clock from Dione, in the edge of the A ring) is the Keeler Gap. See the Wiki, "Subdivisions and structures" at https://en.wikipedia.org/wiki/Rings_of_Saturn.

As with other gaps, the Keeler is associted with a mini moon, Daphnis, but I think what you see is just the Gap! If I zoom into the the photo it just gets grainier, but glad to be corrected if others have a better image.
John

[Victoria]

Kindly help me spot Pandora

[orin stepanek]

Kindly help me spot Pandora

At the right end of the rings!