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| =A Very Strange Crater= | | =A Very Strange Crater= |
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| + | <p>[[File:Daniell-Clem.jpg|Daniell-Clem.jpg]]<br /> |
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− | <p>[[File:Daniell-Clem.jpg|Daniell-Clem.jpg]]<br />
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| <em>image by Clementine from USGS [http://pdsmaps.wr.usgs.gov/PDS/public/explorer/html/moonintm.htm Map-A-Planet]</em></p> | | <em>image by Clementine from USGS [http://pdsmaps.wr.usgs.gov/PDS/public/explorer/html/moonintm.htm Map-A-Planet]</em></p> |
− | <p>While looking at Clementine images of the [http://www.lpod.org/?m=20061025 rille] north-east of Posidonius I noticed for the first time the strange floor of the crater Daniell. This is an elongated crater 23 km across but 30 km long - it looks like massive slumps of the southern rim caused the lengthening. The smooth floor is [http://www.lpi.usra.edu/resources/cla/info/bi/ darker] than the nearby Lacus Somniorum and looks to be a plateau tilted downward to the north. The southern edge of the plateau is bright and therefore seems to be a scarp, and the same bright edge extends part way up a crack that cuts the middle of the floor from south to north. A few other curved cracks exist along the western and northern edges and a semi-circular one cuts the west side of the floor. I used the word <em>crack</em> because these features do not look like rilles. The largest cracks are about 1 km wide - within the grasp of high resolution amateur imaging. According to spectral mapping the floor is dark because it is covered by a deposit of volcanic ash like the dark spots in the crater Atlas. This may be but I am surprised that the pyroclastic dark material is tightly limited to the plateau and not noticeably on the surrounding slumps, rim or outside terrain. This is a very unusual crater. I speculate that the plateau is a few hundred meter thick pile of lava that was tilted by the southern slumps sliding under it. Possibly the same slump-induced uplift cracked the plate-like plateau. It is possible that pyroclastic material erupted through the cracks but I don’t see much evidence for that. I eagerly await the SMART-1 view of Daniell!</p> | + | <p>While looking at Clementine images of the [[October_25,_2006|rille]] north-east of Posidonius I noticed for the first time the strange floor of the crater Daniell. This is an elongated crater 23 km across but 30 km long - it looks like massive slumps of the southern rim caused the lengthening. The smooth floor is [http://www.lpi.usra.edu/resources/cla/info/bi/ darker] than the nearby Lacus Somniorum and looks to be a plateau tilted downward to the north. The southern edge of the plateau is bright and therefore seems to be a scarp, and the same bright edge extends part way up a crack that cuts the middle of the floor from south to north. A few other curved cracks exist along the western and northern edges and a semi-circular one cuts the west side of the floor. I used the word <em>crack</em> because these features do not look like rilles. The largest cracks are about 1 km wide - within the grasp of high resolution amateur imaging. According to spectral mapping the floor is dark because it is covered by a deposit of volcanic ash like the dark spots in the crater Atlas. This may be but I am surprised that the pyroclastic dark material is tightly limited to the plateau and not noticeably on the surrounding slumps, rim or outside terrain. This is a very unusual crater. I speculate that the plateau is a few hundred meter thick pile of lava that was tilted by the southern slumps sliding under it. Possibly the same slump-induced uplift cracked the plate-like plateau. It is possible that pyroclastic material erupted through the cracks but I don’t see much evidence for that. I eagerly await the SMART-1 view of Daniell!</p> |
| <p>[mailto:tychocrater@yahoo.com Chuck Wood]</p> | | <p>[mailto:tychocrater@yahoo.com Chuck Wood]</p> |
| <p><strong>Related Links:</strong><br /> | | <p><strong>Related Links:</strong><br /> |
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| [http://www.lpi.usra.edu/resources/apollo/frame/?AS15-91-12365 Apollo 15 view]<br /> | | [http://www.lpi.usra.edu/resources/apollo/frame/?AS15-91-12365 Apollo 15 view]<br /> |
| [http://www.lpi.usra.edu/resources/lunar_orbiter/images/img/iv_079_h1.jpg A Lunar Orbiter IV view]</p> | | [http://www.lpi.usra.edu/resources/lunar_orbiter/images/img/iv_079_h1.jpg A Lunar Orbiter IV view]</p> |
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| + | <p><b>Yesterday's LPOD:</b> [[October 26, 2006|Moving Sideways]] </p> |
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| + | <p><b>Tomorrow's LPOD:</b> [[October 28, 2006|A Dome or No Dome?]] </p> |
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− | ===COMMENTS?===
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