Re: [Utah-astronomy] Torricelli and Sinus Asperitatis - Ealing 20080608
To follow-up on my pics with the geologic story of this lunar region - the story involves surface burial of the Sinus Asperitatis bay with ejecta from Theophilus. As Chuck Wood's _Modern Moon_ notes, the eject melt blanket north of the Theophilus is one of the few on the Moon that are perfectly preserve. The second part of the Sinus Asperitatis - for me - is how it illustrates who perception of features depends on resolution. Theophilus buried the bay. The GLAC map illusrates the boundary of the heavy melt deposit region ejected from Theophilus. http://gallery.utahastronomy.com/main.php?g2_itemId=11517 This thick deposit is seen as the hommocky terrain south of the mesa shown in my pic - http://gallery.utahastronomy.com/main.php?g2_itemId=11507 - and in the fiducial expert imager pics by - Elias Chasiotis http://lpod.org/coppermine/displayimage.php?pos=-1126 and - Riccardo Cosenz http://www.lpod.org/?m=20071006 The extent of the melt blanket is visible at high sun angles, as shown in the Clementine composite. http://gallery.utahastronomy.com/main.php?g2_itemId=11511 A quesion in my mind about the bay is how far north the eject blanket extends. The Clementine False Color ratio map seems to show it going as far north near the mouth of the bay at Torricelli B and C. http://gallery.utahastronomy.com/main.php?g2_itemId=11515 But it is unclear to me how much of this overburden material is from Theophilus and how much from other impacts. In this regard, the craterlet impacts north of the mesa and west of Torricelli act as depth probes. If the crater extends into the mare region below, darker mare basalts would be brought to the surface. This principle is seen at the one ALPO dark halo crater in the bay - Torrecilli B. Torrecilli B appears on both the Clementine false color ratio and the USGS NIR false color ratio maps as a dark halo crater that excavates deeper mare materials from under an overburden. http://gallery.utahastronomy.com/main.php?g2_itemId=11515 But Torricellie B is at the north end of bay - towards the thin end of a plain covered with ejecta overburden. The craterlets on plain west of Torrecilli - shown on the GLAC map - http://gallery.utahastronomy.com/main.php?g2_itemId=11517 - and in a NIR closeup image of the vicinity around Torrecilli - http://gallery.utahastronomy.com/main.php?g2_itemId=11519 - appears to show that the craterlets are not piercing the full depth of the overburden. Torrecilli seems to have excavated down to a layer of dark materials seen in its smaller western half and on the flanks of its eastern wall. The ability to perceive a feature's true nature depends on resolution. Comparing my my low resoluion pic with the expert imagers, small craters next to hills visually merged together into smooth terrain - http://gallery.utahastronomy.com/main.php?g2_itemId=11507 http://lpod.org/coppermine/displayimage.php?pos=-1126 http://www.lpod.org/?m=20071006 In this sense, my image is not "true" image - a good representation of the surface terrain. The expert imagers show a relatively smooth terrain south of Torricelli and between Torricelli and the meas. But the two negative split image of the region south of Torricelli shown in LTO 78B3 - http://gallery.utahastronomy.com/main.php?g2_itemId=11521 - is as to the expert image pics as their pics are to mine. In LTO 78B3, the "smooth" plain in the expert imager pics becomes a tortured rough surface. However, in LTO78B3 - looking at the original whole map - it is evident that two photographs of differing resolution have been merged together - with a seam line running at the end of the thick Theophilus ejecta melt. The rough terrain in the south end of LTO78B3 appears to continue north to Torricelli. http://www.lpi.usra.edu/resources/mapcatalog/LTO/lto78b3_1/ How a terrain is perceived and interperted heavily depends on resolution. - Kurt
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Canopus56