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| <p>[[File:Mersenius-Grenier-video0069-07-11-21-21-04-07.jpg|Mersenius-Grenier-video0069-07-11-21-21-04-07.jpg]]<br /> | | <p>[[File:Mersenius-Grenier-video0069-07-11-21-21-04-07.jpg|Mersenius-Grenier-video0069-07-11-21-21-04-07.jpg]]<br /> |
| <em>image by [mailto:jeromegrenier@free.fr Jérôme Grenier], Paris, France.</em></p> | | <em>image by [mailto:jeromegrenier@free.fr Jérôme Grenier], Paris, France.</em></p> |
− | <p>Floor-fractured craters are the most interesting ones on the Moon because of their concentration of rilles, dark halo craters and uplifted centers. While some have easily visible rilles ([http://www.lpod.org/?m=20071129 Posidonius] and [http://www.lpod.org/?m=20060309 Gassendi], for example) others have such narrow rilles that they are rarely imaged. [[October_6,_2004|Cleomedes]] is an example of the latter, and so is Mersenius, shown above. Mersenius has long been known for its convex floor, although I am unaware of any measures of its height other than Neison’s statement in his 1876 book, <em>The Moon</em>, that <em> the centre is perhaps 1500 ft higher than the foot of the walls.</em> Schmidt detected two rilles on the floor, but they have been difficult for observers to consistently depict. Jérôme’s image - only the second [[April_3,_2004|one]] to clearly show them - reveals most of the rilles known from Lunar Orbiter IV photography. The rilles crudely circle the floor, especially on the south, west and north, and a very faint one cuts across the nearly featureless southeast quadrant of the floor. Although it is not visible here, on the high Sun Clementine [http://the-moon.wikispaces.com/Mersenius image] four dark pyroclastic deposits are visible along the western edge of the floor. At least one dark spot is from a dark halo crater on a rille. A question that I don’t have a definite answer for is why do Mersenius and Cleomedes have such narrow rilles while most floor-fractured craters have broader ones? Presumably the amount of floor fracturing - and thus rille width - is related to the amount of bending from uplift of the floor. Do these two craters have less uplift than Gassendi, Posidonius and Alphonsus?</p> | + | <p>Floor-fractured craters are the most interesting ones on the Moon because of their concentration of rilles, dark halo craters and uplifted centers. While some have easily visible rilles ([[November_29,_2007|Posidonius]] and [[March_9,_2006|image]] four dark pyroclastic deposits are visible along the western edge of the floor. At least one dark spot is from a dark halo crater on a rille. A question that I don’t have a definite answer for is why do Mersenius and Cleomedes have such narrow rilles while most floor-fractured craters have broader ones? Presumably the amount of floor fracturing - and thus rille width - is related to the amount of bending from uplift of the floor. Do these two craters have less uplift than Gassendi, Posidonius and Alphonsus?</p> |
| <p>[mailto:tychocrater@yahoo.com Chuck Wood]</p> | | <p>[mailto:tychocrater@yahoo.com Chuck Wood]</p> |
| <p><strong>Technical Details:</strong><br /> | | <p><strong>Technical Details:</strong><br /> |
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| Rükl chart 51<br /> | | Rükl chart 51<br /> |
| [http://www.lpi.usra.edu/resources/lunar_orbiter/bin/info.shtml?418 Lunar Orbiter IV view]</p> | | [http://www.lpi.usra.edu/resources/lunar_orbiter/bin/info.shtml?418 Lunar Orbiter IV view]</p> |
− | <p><b>Yesterday's LPOD:</b> [[November 29, 2007|Not From Orbit]] </p> | + | <p><b>Yesterday's LPOD:</b> [[November 29, 2007|Not from Orbit]] </p> |
| <p><b>Tomorrow's LPOD:</b> [[December 1, 2007|Another Lunar Atlas?]] </p> | | <p><b>Tomorrow's LPOD:</b> [[December 1, 2007|Another Lunar Atlas?]] </p> |
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