On a ring origin of the equatorial ridge of Iapetus |
On a ring origin of the equatorial ridge of Iapetus |
Guest_AlexBlackwell_* |
Aug 29 2006, 06:18 PM
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Guests |
Wing Ip just had an interesting Iapetus-related paper published in GRL.
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Sep 8 2006, 05:54 PM
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Director of Galilean Photography Group: Members Posts: 896 Joined: 15-July 04 From: Austin, TX Member No.: 93 |
I still don't see how the two divergent ridges get created by a decaying ring. The orbital speed of the ring at low altitude would not be the same as the rotational velocity of a proto-Iapetus. So, how do the angled ridges get created?? If the ring was at an angle to Iapetus, as it descended it would not stay above a single location.
I favor a tectonic explaination. We have symmetrical ridges here on Earth due to seafloor spreading. Seems like a reasonable explaination to me. The question would be why would there be a single crack along a great circle? Maybe Iapetus had a Europa-like episode with a shallow ocean, and as it slowly froze it expanded/contracted enough to crack open. Without nearby moons and tides, the crack went around the planet symmetrically. -------------------- Space Enthusiast Richard Hendricks
-- "The engineers, as usual, made a tremendous fuss. Again as usual, they did the job in half the time they had dismissed as being absolutely impossible." --Rescue Party, Arthur C Clarke Mother Nature is the final inspector of all quality. |
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Sep 8 2006, 08:29 PM
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Member Group: Members Posts: 288 Joined: 28-September 05 From: Orion arm Member No.: 516 |
QUOTE 37th DPS Meeting, 4-9 September 2005 Session 47 Icy Satellites [47.08] The topography of Iapetus' leading side B. Giese (DLR-Institute of Planetary Research, Berlin, Germany), T. Denk, G. Neukum (Institut fur Geologische Wissenschaften, Freie Univ. Berlin, Germany), C. C. Porco (Cassini Imaging Central Laboratory for Operations, Space Science Institute, Boulder, CO, USA), T. Roatsch, R. Wagner (DLR-Institute of Planetary Research, Berlin, Germany) We have used Cassini-stereo images to derive a topographic model of Iapetus' leading side. The model reveals that Iapetus has substantial topography with heights (referenced to a 747 x 744 x 713 km ellipsoid (Thomas et al., in preparation)) in the range of -9 km to +15 km... Hhm, this strange ellipsoid figure could be a hint for some internal force once having driven a probable tectonic mechanism and causing the ridge... |
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Sep 9 2006, 08:59 AM
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Senior Member Group: Members Posts: 3516 Joined: 4-November 05 From: North Wales Member No.: 542 |
Hhm, this strange ellipsoid figure could be a hint for some internal force once having driven a probable tectonic mechanism and causing the ridge... . . or the fossil tidal bulge produced by a close-orbiting subsatellite. I notice nobody else fancies this origin for the ring material - is it ridiculous for some reason that I have failed to notice? On a philosophical note: Assuming the sceptics are wrong (and I leave that one to tasp) I think we are responding here to a real eureka moment in planetary science, perhaps on a par with Vine and Matthews. When we study the planets we have become accustomed to looking for evidence of mantle convection or crustal plate movement. Now, for bodies with primitive surfaces at least, we will always have to ask the question 'Is there any evidence of a former ring?' |
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