New Iapetian image series |
New Iapetian image series |
Sep 11 2006, 09:27 PM
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#1
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Member Group: Members Posts: 288 Joined: 28-September 05 From: Orion arm Member No.: 516 |
Hi,
CASSINI has transmitted 184 pics (!) over the last days. Here five takeouts, 3-4x enlargement: Date: 2009-09-06 Distance: 2.228.548 km Filters: CL1 and CL2 Date: 2009-09-08 Distance: 3.215.284 km Filters: P120 and GRN Date: 2009-09-08 Distance: 3.216.610 km Filters: P60 and GRN Date: 2009-09-09 Distance: 3.390.271km Filters: P60 and GRN Date: 2009-09-09 Distance: 3.427.313 km Filters: P120 and GRN Maybe somebody is able to combine some of those images to show more details. Bye. |
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Feb 14 2007, 11:25 PM
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#2
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Merciless Robot Group: Admin Posts: 8785 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
Huh...that "yin-yang" aspect makes Iapetus look like one of the hemispherical views of Fritz Leiber's The Wanderer...art imitating life in yet another subtle way, albeit decades in advance.
Just struck me also how deep & pronounced all these craters are in comparison to those on the inner large icy moons. Is this difference perhaps due to fallout from Enceladus on the latter, as discussed on another thread, or are we seeing evidence of a thicker crust on Iapetus? -------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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Feb 15 2007, 12:00 AM
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#3
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
Huh...that "yin-yang" aspect makes Iapetus look like one of the hemispherical views of Fritz Leiber's The Wanderer...art imitating life in yet another subtle way, albeit decades in advance. Just struck me also how deep & pronounced all these craters are in comparison to those on the inner large icy moons. Is this difference perhaps due to fallout from Enceladus on the latter, as discussed on another thread, or are we seeing evidence of a thicker crust on Iapetus? Remembering that Iapetus is a startling outlier (literally and figuratively) in terms of its distance from its primary (only likely captured asteroids rival it among the natural satellites in the solar system), I suggest that its distance is the prime causative factor. Look at the crusts of Mercury and the Moon and the Moon's maria. They are all three "old". The oldest crust there is not much more than 25% older than the youngest. But the rate of cratering is profoundly different: The cratering rate changed so sharply around 4 GYA that relatively minor differences in age led to tremendous differences in the preserved-for-all-time proportions of craters left behind. I think the difference between Iapetus on the one hand and Rhea on the other (virtually identical size and distance from the Sun) is that the heat of proto-Saturn kept Rhea slushy just a bit longer, letting its primordial lumps from coalescing round out and its largest proto-impacts to fade into the slush. Iapetus cooled faster and has kept its original lumps in a way that no body outside the asteroid belt could have because all the planets are too large and all the other midsize satellites are too close to their primaries. As a result, Ceres and Iapetus are less spherical than Rhea, Titania, and Oberon, and even some of the smaller icy satellites of Saturn and Uranus. The large craters are just another manifestation of the big, early impacts having been left untouched by any general crustal slushiness during that period. |
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