by Bob Jardine
It was probably a crater, right on the terminator. Pretty small crater. The Eastern rim was in the light -- perhaps about a 60 degree arc. The entire floor of the (presumed) crater was in darkness. Around what I presumed was the rest of the rim were exactly 5 bright dots -- four of them equally bright, and one dimmer one. The four bright ones were spaced around the imaginary rim at apparently perfect intervals -- like four points of a perfect pentagon, with the position of the fifth apex being in approximately the center of the Eastern arc that was lit. The fifth dot spoiled the symmetry slightly, but it could be ignored because it was much dimmer than the rest -- in fact, it wasn't always there.
It is difficult to describe this feature -- the circle was so perfect, the spacing of the four bright dots was so perfect, and the dots were so small and bright -- just tiny pinpoints against perfect darkness. It was really quite something. (The symmetry was so perfect, it almost looked artificial.)
I pulled out my map and tried to figure out what the crater was. After a bit of study, I could easily orient myself with the following features -- Messiers A and B and the bright ray streaming West from there, Mare Nectaris and Rosse, Fracastorius and Beaumont (the latter like the heel-print of a large boot on the Western edge of Nectaris), and Piccolomini, with its obvious central peak lit up nicely above the dark floor, and the Eastern-most part of Rupes Altai curving away like a tail on Piccolomini, fading off into the darkness.
The feature that I was seeing was a little bit SW of the midpoint of the line from Beaumont to Fracastorius. I suspect it may have been Polybius, which is about the right size and in more or less the right place, but the feature I was seeing seemed to me to be closer than the map shows Polybius is to both Beaumont and Fracastorius. Maybe this difference is just a perspective problem.
Of course, I've seen central peaks in the sunlight when the floor was in darkness before, and I've seen partial crater rims isolated in sunlight before, but never anything quite so spectacular and unique as this.
Has anyone seen anything like this? Better yet, has anyone seen this very feature? Any info would be appreciated.
This feature is definitely going to have me out looking for it again!
Posted on sf-bay-tac Jun 13, 2005 23:03:14 PT
Converted by report.pm 1.2 Sep 25, 2005 07:55:18 PT