May 7, 2009
A Rille That Doesn't Know What To Do with Itself
image by Alex Sanz, Ayllón, Spain
Posidonius has one of the weirdest rilles on the Moon. Not the linear ones on the older tilted plateau, but the super sinuous one that starts at the northern (upper part) rim and hugs it until it strikes off across a lava plain. And then after following a long ridge (part of the subsided terraces that had been uplifted?) bends sharply towards the western rim. It stays a few kilometers from the rim and meanders to the north until it reaches the low spot - a real gap? - in the rim and stops. A Lunar Orbiter IV image shows that the rille just stops against the other side of the gap. Weird. In Alex's image and in the Lunar Orbiter IV one you can see that this entire rille is very tightly curving with closely spaced bends. On Earth such tight meanders occur in rivers when the slope is very gentle. This is probably true on the floor of Posidonius - when the full resolution Kaguya altimeter map is ultimately produced I predict that the slope where the hyper sinuous rille is will be seen to be nearly flat.
2 May 2009. 20:03 UT. SCT 11" f/30 + DMK 31AU03 camera. Processing: Registax5, MaxIm and PS CS2
Rükl plate 14
Yesterday's LPOD: A Museum Piece
Tomorrow's LPOD: What is LPOD About?