February 9, 2013

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Unequal Ejecta

image by Stefan Buda, Melbourne, Australia

Stefan sent this image, commenting that I probably wouldn't use it because similar views have appeared earlier in LPOD. But sometimes an image of a familar area brings to mind things that weren't noticed before. This one does that. The large crater is Delisle with 18 km wide Diophantus to the south and a little west. The rille between the two is difficult to detect telescopically, whereas the one near the center of the image is easier - at least its 2 km wide vent trough is. I wish I understood why sinuous rilles often start in such large, well-defined troughs and then assume their standard narrower, sinuous courses. Other features here that might be missed - but I increased the image contrast to bring them out - are the lava flows near bottom right. These are not as sharply defined as the nearby flows closer to La Hire. What I newly noticed in this image was the uneven distribution of ejecta from Delisle. Ejecta extends slightly more than one crater diameter to the east, to the north, and probably the south (the rille makes it visually confusing), but not to the west. It looks like the Delisle Mountain (the Baby) blocked the movement of ejecta; if so, the ejecta flowed across the landscape instead of moving in ballistic arcs. A weakness of this theory is that mare lavas occupy some of the space between the Baby and the edge of Delisle. I don't think the lava is younger than Delisle but I also don't know why the ejecta didn't cover it. The best interpretation is still that the mountain blocked the ejecta, but there are poorly understood complications.

Chuck Wood
PS: And for Danny I have to mention the odd ray pattern from Samir.

Technical Details
2013 February the 5th, 19:05 UT. 405mm Dall-Kirkham and DMK21AU04. Four panel mosaic processed with Registax6 and Canon PhotoStitch.

Related Links
Rükl plates 9 & 19
21st Century Atlas chart 21.
Stefan receiving an imaging award from David Malin

Yesterday's LPOD: Among the Astrophysicists

Tomorrow's LPOD: Hidden Roughness


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