Millikan

D=82 km
Center: 43¡N, 137¡E

Count Area: 2111 km^2
Observed Density (@ 1km): 29400 ± 3800
Age: [4.0 ± 0.1 (+sec: 4.1)]
Stoffler epoch: [Pre-Nectarian]
Fit Density (@ 1km): [52800 ± 10300]
PF fit: good?, a few small crater bins shallow, larger ones are OK, many secondaries

Age calculation notes:
- poor fit - anchored at large D. Fit not greatly improved by using Hausen and Holsapple scaling law or layering (SM).
- poor fit at small craters (up to ~ 1.3 km) - good fit for large ("right ear" only defined by one crater) - small craters likely effected by geology processes, but could perhaps be strength - try strength model; adding OSs weakens fit and produces slightly older age. Fit only slightly improved, but not enough to be considered good when using Hausen and Holsapple (SN) scaling - use w/o scaling. Geology is a strong candidate - large fresh crater nearby - large fresh crater within - lots of mid-sized secondary chains/clusters. (MRK)

USGS geology: 
Crater rim mapped as Nectarian. Crater floor mapped as fill with a Early Imbrian to Nectarian age.

Wilhelms: 
Nectarian (all materials)

Floor material: 
Best guess is not original. Relatively flat floor, edges meeting wall look embayed, small central peak. Material looks degraded. Soft?

Geology Observations: 
Ejecta blanket severely eroded. Rim looks somewhat sharp? Small central peak that looks eroded. Some possible wall collapses on southern portion (excluded). Floor relatively smooth, but does have a "textured" look to it. Many secondary chains/clusters with largish craters (up to ~ 4 km) of various degradation states.

SFD Observations: 
This SFD is unusual in a couple of ways. First it has the usual steep then shallow distribution, but it is shifted to larger diameters on the R-plot (to the right) compared to most of the other SFDs. The change point is at ~ 3-4 km rather than 1-1.5. Second, the SFD becomes shallow again for small craters (< 1 km). I have been trying to figure out if this is a roll-off due to resolution, but I have picked a fairly conservative value of 800 m for the data cutoff and rechecked the image. There do seem to be a lot of "texture" at about that size, which may be very degraded craters that we are missing. It is interesting to note that the class 1 & 2 craters don't show this feature just the degraded classes. Perhaps the production of several large craters (including the recent one in the north), including large secondaries, has "temporarily reset the smallest craters? Also OS SFD is intriguing. Note shallow "right ear" defined by only one crater. Slope (Diff)=3.2 ± 0.3.

Discussion notes: 
change floor from "not likely" to "possible". lack of small craters -> texture makes difficult to see small craters. Also fair amount of secondaries, perhaps not good for PF comparison and age.

Notes from Brian's adjustment:
- Counting boundary:
	Not bad - but the boundary on the right side could shrink a bit since
it appears to include some of the crater wall.
	Some craters on the left half of the image were missed (some are
texture though)

- Secondaries:
	Some large crater clusters are only partially marked.

- Removal of large, buried craters:
	No improper large craters.

- Size adjustment of large craters:
	Looks OK.
	Removed a class 3 crater at 11:00 position (BE & MRK).

- Explaining unusual cases:

- Future actions:
	Minor boundary change?
	Completed (MRK).

- Completed actions:
	Add more craters into some clusters (BLE).
	Mark missing craters, mostly on left side.
	I also added more craters both "primary" and "secondary" (MRK).

Last Edited by MRK 12/17/2012