February 12, 2019
Originally published December 4, 2009
north to left image by Howard Eskildsen
We don't understand rays well enough. Back in 1960 Shoemaker showed that they were ejecta from impact craters, and sometime in the 90s B. Ray Hawke and his colleagues recognized that rays could have two components, freshly pulverized rocks and bright highland rocks. So we know something about their emplacement and composition. But their shapes and lengths and even their non-radiality are not well understood. The rays emanating from the two little craters on either side of Stevinus are good examples. First, these rays seem to be very long for the small diameters (8 and 12 km) of their source craters. Second, note the broad rays to their north (left) that are not all radial to them - how exactly, do non-radial rays form? And, as we've commented before. the shapes of rays have never been studied and classified. Who will be a champion ray researcher?
11/30/2009; 02:08 UT. Meade 6", f/8 Refractor + DMK 41AU02.AS, 2-image composite
Rükl plates 59 & 69