Date: 10/03/2016 12:16:17
From: mollwollfumble
ID: 857627
Subject: Rings of saturn

I’m still peeved that Cassini has not yet, to my knowledge, taken even one close up picture of a ring particle. I appreciate that the camera is shielded when passing through the plane of the rings to avoid impact damage, but still.

Wikipedia thoroughly contradicts itself when talking about the ring particles. In one place it has “ranging in size from micrometres to metres” and in another place “composed of particles ranging in size from 1 centimetre to 10 meters”. That’s a heck of an inconsistency, like a factor of 10 or more. When I look up the reference for the first of these two statements it gets even worse “ranging in size from boulders as large as small apartment buildings to fine, dust-sized specks”, and that’s from the Cassini team! When I look up the second reference it’s from 1985, so that’s hardly current. This 1985 data is from Voyager and gives an upper limit on A ring particle diameter, according to a paper from 2015, of 7 metres.

But there is at least some recent information. From 2015, “minimum particle size is 4.5 mm, for outermost A ring.” “minimum particle size is 15 mm for particles near Encke Gap”.

The ring thickness is also inconsistent between different sources, but at least here we have the explanation that different rings have different thicknesses. Thickness estimates range from “as little as 10 metres to as much as 1 kilometre “.

More information wanted, Cassini, pull your finger out.

On another Cassini topic, an island a couple of km long has appeared in a lake on Titan and disappeared again since Cassini arrived. See apod from a couple of days ago for details.

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Date: 10/03/2016 13:12:13
From: dv
ID: 857639
Subject: re: Rings of saturn

I don’t see how it would be possible.

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Date: 10/03/2016 13:16:01
From: dv
ID: 857642
Subject: re: Rings of saturn

Basically given the relative speeds and particle sizes, you couldn’t expect Cassini to image an individual particle.

Perhaps some future mission will include a probe to be placed in a ring orbit.

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Date: 10/03/2016 13:18:26
From: Cymek
ID: 857645
Subject: re: Rings of saturn

dv said:


Basically given the relative speeds and particle sizes, you couldn’t expect Cassini to image an individual particle.

Perhaps some future mission will include a probe to be placed in a ring orbit.

And look for Von Neumann machines

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Date: 10/03/2016 13:26:47
From: Dropbear
ID: 857649
Subject: re: Rings of saturn

hello Neumann

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Date: 10/03/2016 15:56:41
From: mollwollfumble
ID: 857748
Subject: re: Rings of saturn

dv said:


Basically given the relative speeds and particle sizes, you couldn’t expect Cassini to image an individual particle.

Perhaps some future mission will include a probe to be placed in a ring orbit.


I would love Cassini to end it’s mission parked among the rings, but it isn’t going to happen. What I think they could do though is take backwards facing shots straight after passing through the plane.

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Date: 10/03/2016 15:58:17
From: Dropbear
ID: 857749
Subject: re: Rings of saturn

why would there be high relative speeds of ring particles anyway??

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Date: 10/03/2016 16:04:36
From: dv
ID: 857750
Subject: re: Rings of saturn

Dropbear said:


why would there be high relative speeds of ring particles anyway??

There are high relative speeds between the Cassini craft and the particles in the rings, in comparison to the dimensions of the particles (which are up to a few metres or so).

There are high relative speeds between Cassini and Titan and Enceladus etc but they are very large …

cf I can take a picture of the statue of liberty as I zoom past it in a cab but I can’t take a picture of an ant while I zoom past it in a cab.

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Date: 10/03/2016 16:08:25
From: Dropbear
ID: 857751
Subject: re: Rings of saturn

dv said:


Dropbear said:

why would there be high relative speeds of ring particles anyway??

There are high relative speeds between the Cassini craft and the particles in the rings, in comparison to the dimensions of the particles (which are up to a few metres or so).

There are high relative speeds between Cassini and Titan and Enceladus etc but they are very large …

cf I can take a picture of the statue of liberty as I zoom past it in a cab but I can’t take a picture of an ant while I zoom past it in a cab.

sorry, I thought you were implying high relative speeds between ring particles

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Date: 10/03/2016 16:17:34
From: mollwollfumble
ID: 857753
Subject: re: Rings of saturn

dv said:


Dropbear said:

why would there be high relative speeds of ring particles anyway??

There are high relative speeds between the Cassini craft and the particles in the rings, in comparison to the dimensions of the particles (which are up to a few metres or so).

There are high relative speeds between Cassini and Titan and Enceladus etc but they are very large …

cf I can take a picture of the statue of liberty as I zoom past it in a cab but I can’t take a picture of an ant while I zoom past it in a cab.


The ant wouldn’t have to be in focus, a streak on the image would be as revealing, or perhaps even more revealing when the spacecraft speed is known. Have to be lucky though, because the ant would have to be close to the camera, difficult to arrange.

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