Mercury Flyby 1 |
Mercury Flyby 1 |
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#301
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Member ![]() ![]() ![]() Group: Members Posts: 258 Joined: 22-December 06 Member No.: 1503 ![]() |
40 days and counting. The long wait is almost over!
I wonder whether we will get enough data to test new simulation theories like this one. http://space.newscientist.com/article/mg19...solar-wind.html What do you expect from this first flyby? |
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#302
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![]() Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 3419 Joined: 9-February 04 From: Minneapolis, MN, USA Member No.: 15 ![]() |
My most overwhelming impression of the surface, especially on the inbound full-crescent views, is that Mercury's LHB-carved surface has been almost completely covered with lava flows. The population of completely expressed large craters / small basins is relatively small, especially as compared to our Moon. The population of these large craters / small basins which are expressed only as circular deformations of a relatively smooth covering layer is very similar to the population of non-covered craters in the lunar highlands.
Conclusion? Mercury was resurfaced (if imperfectly) *after* the LHB, and now only exhibits "uncovered" craters from the three and a half billion years since its end. -the other Doug -------------------- “The trouble ain't that there is too many fools, but that the lightning ain't distributed right.” -Mark Twain
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#303
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![]() Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 1649 Joined: 5-March 05 From: Boulder, CO Member No.: 184 ![]() |
Conclusion? Mercury was resurfaced (if imperfectly) *after* the LHB, and now only exhibits "uncovered" craters from the three and a half billion years since its end. -the other Doug Nice explanation Doug. Sounds like a reasonable hypothesis for the relative lack of Copernicus style craters (as noted for some areas). Does it also explain the prevalance of those double-rimmed ones? -------------------- Steve [ my home page and planetary maps page ]
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#304
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![]() Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 3419 Joined: 9-February 04 From: Minneapolis, MN, USA Member No.: 15 ![]() |
Nice explanation Doug. Sounds like a reasonable hypothesis for the relative lack of Copernicus style craters (at least in some areas). Does it also explain the prevalance of those double-rimmed ones? Actually, Copernicus-style craters are about as common on Mercury as they are on the Moon. Both are post-LHB. What remains to be seen is how ancient these Hermean inter-crater plains might be -- I've seen some areas on both Mariner 10 images and in these new Messenger images where relatively fresh-looking ray systems disappear in relatively dark and smooth lava flows. That could always be a situation where the ejecta was shadowed, God knows we've seen non-continuous ray systems elsewhere. But a very close look at these places is definitely called for, I think. As for the preponderance of double-ring craters, every theory I've heard about it tries to lay this observation at the feet of Mercury's gravity field, which is more intense than the Moon's. However, I've never seen a model that successfully predicts the formation of central rings vs. central peaks that doesn't also have to assume a somewhat greater plasticity of the target to achieve those double rings. -the other Doug -------------------- “The trouble ain't that there is too many fools, but that the lightning ain't distributed right.” -Mark Twain
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