Iapetus Encounter In January |
Iapetus Encounter In January |
Nov 29 2004, 04:38 PM
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Member Group: Members Posts: 154 Joined: 8-June 04 Member No.: 80 |
I heard about a peak on Iapetus that may be taller than Olympus Mons on Mars. I was wondering if the RADAR instrument will be used in the January encounter to verify this. What is the maximum distance the RADAR can be used?
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Dec 18 2004, 11:25 PM
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#2
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Senior Member Group: Members Posts: 1887 Joined: 20-November 04 From: Iowa Member No.: 110 |
Some early science results for Iapetus
In the same session at the Division of Planetary Sciences meeting, Bonnie Buratti of the Jet Propulsion Laboratory reported on the first Visual and Infrared Mapping Spectrometer measurements of Iapetus. The encounter was too distant for VIMS to be able to capture pretty pictures as the cameras did. In fact, Buratti got a laugh from the meeting attendees when she flashed her VIMS "image" up on the screen: a mere four pixels covered the entire moon. But she cautioned the scientists not to laugh so quickly. The VIMS image was "fortunate in outline," she explained. "One of the four pixels sits almost entirely in the bright region, and one in the dark region. So these represent the first resolved spectra of Iapetus." Getting resolved spectra of Iapetus' bright material and dark material means that it's possible for a spectroscopist like Buratti to tell the difference in composition between the light stuff and the dark stuff, and begin to answer the question of how and why Iapetus can have two such different surfaces. The results surprised Buratti. "I may have to eat a lot of stuff that I've published in the past," she said. Looking at infrared wavelengths, she found carbon dioxide bound up in the dark material, just as was seen at Phoebe. This falls in line with the preexisting theory that the dark stuff on Iapetus could have come from Phoebe. But that's not the whole story. "Phoebe and Iapetus are very different in the visible [wavelengths]," Buratti said. In those wavelengths, Iapetus' dark material looks more like D-type asteroids, which are reddish in color, "like Hyperion." Phoebe, by contrast, most closely resembles a more primitive C-type asteroid. Buratti tried to explain how these differences could arise within the Saturn system. "Exogenic small outer satellites," that is, small bodies that formed outside of the Saturn system and were later captured into distant orbits, "could provide additional material that's reddish in visible wavelengths," which would explain the D-type appearance of Iapetus. This hypothesis is reasonable, Buratti said, because "the small outer satellites do have reddish colors in the visible [wavelengths]." But she can't explain why the reddish coloration doesn't also show up on Phoebe. http://www.planetary.org/news/2004/cassini_iapetus_1209.html |
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