Birkeland

D=84 km
Center: 30°S, 174°E

Count Area: 1604 km^2
Observed Density (@ 1km): 13700 ± 2900
Age: 3.8 ± 0.1 (+sec: 3.8)
Stoffler epoch: Early Imbrian
Fit Density (@ 1km): 15200 ± 2800
PF fit: good, large crater data slightly shallower

Age calculation notes:
good for small D, bad for large D (SM).
OK fit (within error for large D - this is a "right ear" crater) - use as is; adding OSs doesn't change fit or age (MRK).

USGS geology: 
All mapped as Eratosthenian crater material.

Wilhelms: 
Eratosthenian

Floor material: 
Best guess is original. But... have a few contacts with rim wall that look embayed and peak is relatively small. Also surrounded by other craters filled with mare. Material looks softened. Soft?

Geology Observations: 
Ejecta blanket visible, but not bright in WAC. Rim looks slightly eroded. Central peak small. Floor mostly flat, but hummocky area to south and west. Secondary chains with small craters (up to ~ 1 km). 3 large craters in a line with similar morphologies in middle of crater - currently not interpreted as secondaries because I cannot figure out where they would have come from, but very suspicious. 

SFD Observations: 
Craters < 1.5 km dominated by class 3, large craters dominated by classes 1 & 2. Distribution < 1.5 km shallower than others for this size range. Possible shallow "right ear" - primarily due to the 3 large, similar morphology craters that may or may not be secondaries/breakup. Slope(Diff)=-3.6 ± 0.3. 

Discussion notes: 
Try strength to improve fit

Last Edited by MRK 11/14/2012