May 18, 2012
Horns And Wings
image by Lambert Spix, Germany
I remember being fascinated by various generations of old BAA* lunar observing reports, and indeed by many of the illustrations in Goodacre's excellent 1931 book, The Moon. Lambert's drawing could come from that period for it is focussed tightly on a single feature, and everything else that a camera would capture is ignored. Many of the classic maps of the 1800s were compiled from hundreds of individual drawings, some of which were of single features. And then, years later, an observer would note something on the Moon that differed from the maps and excitement would reign about changes on the Moon. Drawings are wonderful and often evocative, but they are interpretation and selections rather than unbiased documentations. This drawing of Lambert's depicts a fascinating observation of what he calls the horns of Kies A. Danny Caes had earlier noted this interupted shadow and correlated it with the wings to the west of the crater. Such wings are ejecta ridges often formed by simultaneous impacts of adjacent craters, such as secondaries. They also seem to form at some single craters and perhaps indicate oblique impact. The LRO QuickMap shows that the western rim of Kies A is 350 to 450 m lower than immediately adjacent rim segments, and that the wings reach about 65 m in height. I wonder if the wings contain the material missing from the western rim? A simple model, now possible because of the topographic data, can answer that question.
- British Astronomical Association
Yesterday's LPOD: A Family Affair
Tomorrow's LPOD: Circumferential Ups And Downs