image by Jérôme Grenier, France

Many images submitted to LPOD competently depict a feature but don't add to our understanding. This outstanding one from Jérôme is the kind of image that makes my heart sing. Perhaps every detail shown has been seen previously but this is a stunning image of Fracastorius. Cutting across the crater floor is the well known rille that is a continuation of the Altai Fault scarp and the boundary separating the northern (top) half of the floor which is covered by younger lava and has subsided, from the older southern surface. Shadows on the right side of the floor indicate that the center of the southern part of the floor is higher than the part near the wall. The large mound of lava just outside the northern rim (if there was one) is very well shown with its summit craterpits. This domelike feature may be the vent for the smoother, younger lavas that drape this southern edge of Mare Nectaris. But it doesn't look like the dome was the source for the younger lavas in northern Fracastorius - they must have erupted onto the floor from fractures under the crater. Outside the rim of Fracastorius and elsewhere some of the older lavas of Nectaris are visible as rougher surfaces.

Chuck Wood

Technical Details
19 October 2008; 02:10 UT. Orion Optics (UK) OMC 12" + barlow 2x + Dmk31AF03 + red filter.

Related Links
Rükl plate 112
Jérôme's website


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