Dawn's Survey Orbit at Ceres |
Dawn's Survey Orbit at Ceres |
Jun 15 2015, 05:47 PM
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Senior Member Group: Members Posts: 1729 Joined: 3-August 06 From: 43° 35' 53" N 1° 26' 35" E Member No.: 1004 |
daily Ceres picture from the survey orbit
http://dawn.jpl.nasa.gov/multimedia/images...tml?id=PIA19572 I started a new topic, as we are no longer in the first orbit phase |
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Jun 23 2015, 07:26 PM
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#2
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Member Group: Members Posts: 153 Joined: 20-December 14 From: Eastbourne, UK Member No.: 7372 |
I also think sublimation of volatiles may be involved in shaping the surface. I have been trying to explain why the bright spots all over Ceres are not covered in Ceres regolith. Either the precesses creating the bright material are very recent, or even current, or some mechanism is slowing down the recovering process.
If we assume the bright material is Water Ice or frozen brine, sublimation rates would be high, creating a significant "breeze" very close to the surface, which could be sufficient to disturb and remove dust. So if volatiles are ejected onto the surface it may take a considerable length of time for them to be recovered in dust. This image, highly upscaled and zoomed, is of the bright spots in "Spot 5". https://www.flickr.com/photos/124013840@N06...eposted-public/ My interpretation is the largest bright area, on the left, is a sort of Ice "lava" lake sitting inside a Caldera, possibly still being refreshed from below, though highly unlikely. However, the amount of sublimated gas from such a volume of Ice, could keep the area dust free. On the right flank of this Caldera it can be seen that the mound is constructed in layers and lighter, but not bright, "lava" flows can be seen radiating from the central Caldera. Smaller eruptive sites nearby could also create the smaller blotches, they also have slightly lighter "lava" flows radiating from them. They could also be depressions or small craters filled up with fluid ejecta from the larger Cryovolcanos or "Hot Springs", "Geysers" and mud Cryovolcanos. The farthest right appears to have built a sizeable cone too. Once again the resolution is not quite good enough to be sure and a small degree of interpretive license is required. It looks to me that this is, or was, a Cryovolcanically active region. The deep crater it is situated in, suggests the thickness of the Ice crust is very thin in the bottom of the crater and the original impact may have opened a crack in the crust either temporarily or possibly it is still there. Others have traced a fault line running through the crater that appears to run up the right side of the large Caldera, although it could be interpreted as a channel carved by "hot" liquid erupting from the Cryovolcano, it has a "river" like appearance. |
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