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Rev 127 - Feb 22-Mar 12, 2010 - Rhea R2 and Helene, Also distant Iapetus
DrShank
post Feb 26 2010, 09:34 PM
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QUOTE (Elias @ Feb 26 2010, 03:20 PM) *
But the equatorial features may simply indicate that there was a ring sometime in the past, and its collapse has formed them. Is that right? Its not necessary that the ring system/disk still exists (although in the context of the MIMI observations, one may assume that).


yes that is true, we cant determine the date of the equatorial features. they could be very recent or not forming today.
one thing is fairly clear is they are not ancient or they would have been erased by now!
paul


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ugordan
post Feb 26 2010, 09:39 PM
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QUOTE (DrShank @ Feb 26 2010, 10:34 PM) *
one thing is fairly clear is they are not ancient or they would have been erased by now!

I.e. they wouldn't be as UV-bright as they are.


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jasedm
post Feb 27 2010, 05:20 PM
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QUOTE (Elias @ Feb 26 2010, 05:40 PM) *
I am not sure if MIMI data can confirm the disk/rings scenario. What MIMI data may tell us is whether the structures that will be observed during the flyby in electrons and ions, under a much different geometry compared to the two previous flybys, are consistent with that exciting scenario (or not). Consistent observations under much different geometries, may strengthen the initial interpretation, but definitely not prove it.

I think proof can only come from imaging observations (or maybe other, more direct methods than those based primarily on charged particle data).



This may be pertinent:

From the latest Cassini significant events report:

"ULO has received an absolute timed real-time command file from the Cosmic Dust Analyzer instrument team. Starting on DOY-061T16:00, the commands will customize the instrument's visibility to bigger particles during the upcoming Rhea flyby on Mar. 2 and the following periapse passage. The command approval meeting for this file is scheduled for Thursday, Feb. 25.'
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Hungry4info
post Feb 28 2010, 02:27 PM
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Quick, dirty gif of a mutual event with Dione and ... Rhea?
(That guess is based off what I found in Celestia unsure.gif I suspect it's Cassini trajectory is out of date.)
Attached thumbnail(s)
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volcanopele
post Feb 28 2010, 08:57 PM
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QUOTE (Hungry4info @ Feb 28 2010, 07:27 AM) *
a mutual event with Dione and ... Rhea?

From the Rev127 Looking Ahead article: "Also on February 24, Cassini will observe Dione partially occult Enceladus and its south polar plume. During this observation, Dione will be 2.04 million kilometers (1.27 million miles) away from Cassini and Enceladus 2.27 million kilometers (1.41 million miles) away."


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Elias
post Mar 2 2010, 02:19 PM
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QUOTE (DrShank @ Feb 26 2010, 10:34 PM) *
yes that is true, we cant determine the date of the equatorial features. they could be very recent or not forming today.
one thing is fairly clear is they are not ancient or they would have been erased by now!
paul


Thanks for the clarification. How can such structures be erased in a inactive moon? Charged particles or interplanetary dust impacts for instance? The E-ring dust can only modify the trailing hemisphere, I assume.


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tasp
post Mar 2 2010, 04:22 PM
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I am not sure if this would be compression artifacts or just maybe a quirk of the pixel geometry due to the differing colors, but some of the ridges and crater rims in the lower portion of the RH image in post 6 seem to have very fine crenelation (for lack of a better word).

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peter59
post Mar 2 2010, 05:14 PM
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Interesting JPL blog with a fantastic movie made by Cassini navigator Brent Buffington that shows each of the activities performed during Rhea flyby.
http://saturn.jpl.nasa.gov/video/videodetails/?videoID=207


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ugordan
post Mar 2 2010, 10:04 PM
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Enceladus, plume and rings, RGB:
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volcanopele
post Mar 3 2010, 09:37 AM
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Animation of Helene flyby just uploaded to youtube (may take 30-60 minutes to finish processing, so be patient):

http://www.youtube.com/watch?v=0aVbvAojQlw

Only 4 hours and 4 minutes until Helene closest approach!


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ugordan
post Mar 3 2010, 10:20 AM
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Rhea images have started coming down:
http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=214324
http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=214340
http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=214348
http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=214356
http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=214378


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Astro0
post Mar 3 2010, 01:28 PM
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Handstitched mosaic of Rhea. Image sequence N00152147,51,55,59,67,75,83,91 taken on March 02, 2010 and received on Earth March 03, 2010.
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Ian R
post Mar 3 2010, 01:32 PM
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Here's a global colour view of Rhea (IR-GR-VIO):

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Guest_Sunspot_*
post Mar 3 2010, 01:41 PM
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QUOTE (ugordan @ Mar 3 2010, 10:20 AM) *


Is that vertical stripe in your first image some kind of image artefact?
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ugordan
post Mar 3 2010, 01:54 PM
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No, it's a real crack.


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