Rosenberger

D=92 km
Center: 56¡S, 43¡E

Count Area: 1808 km^2
Observed Density (@ 1km): 17200 ± 3100
Age: [3.8 ± 0.1 (+sec: 4.1)]
Stoffler epoch: [Nectarian]
Fit Density (@ 1km): [18900 ± 6300]
PF fit: poor, craters above D ~ 1.5 km shallow (~ 20 total), and need to remove 6 largest to get fit

Age calculation notes:
- poor fit - anchored at intermediate D. Layering with thickness H=0.26km and the top layer has Y=2e7, the bottom layer has Y=2e8 improves fit (SM).
- bad fit - distribution shallow - maybe geology - but strength also a possibility - try different scaling law; adding OSs does not change fit, but does increase age slightly. Using layers with differing strengths (LrN) improves fit and reduces age (MRK).
- why does using layering work? Including a change in strength causes the PF to kink and shift for small D (transition occurs D ~ 1 km), which is why the fit is better. But is there justification for using this law here and not with other craters (i.e., is geology different)? The surface does have a weathered look, but can see areas that look more "solid". There are partially filled larger craters indicating a thin layer of fill (which we see on other craters w/o kink). So a thin "weak" layer over a stronger layer is not unreasonable. Note a resurfacing event that removes small craters preferentially can produce the same effect and terrains of two ages. Although a region of of lower small crater density does not pop out. (MRK)

USGS geology: 
Crater rim mapped as Pre-Nectarian. Crater floor mapped as fill with a Nectarian age.

Wilhelms: 
Pre-Nectarian (all materials)

Floor material: 
Best guess is not original (for area counted). Relatively flat floor, material has sharp contact with wall, small central peak. Material looks relatively fresh. Hard?

Geology Observations: 
Perhaps small areas of ejecta blanket visible near rim. Rim is eroded. Small central peak that looks eroded. Southeast section of floor relatively smooth. Areas to the northwest look as if covered by collapse or ejecta from nearby fresher crater. Several secondary chains/clusters with largish craters (up to ~ 3.5 km) of various degradation states.

SFD Observations: 
Smallest craters < ~ 900 m dominated only by class 3 and 4. As craters get larger they are dominated by less degraded classes. SFD is semi-unusual. Has steep and shallow branches, but the steep branch is cutoff at smaller craters (~ 1 km) and the shallow branch extends to smaller diameters. Shallow "right ear". Slope (Diff)=2.4 ± 0.3

Discussion notes: 
2 craters to left may not be pre-existing. superposition and age backwards with Vlacq => good evidence not original floor. "v" could be real.

Notes from Brian's adjustment:
- Counting boundary:
	Boundary could be shrunk near the bottom of the image.
	Agree (MRK).

- Secondaries:
	A few more clusters and chains could be marked, but not bad.

- Removal of large, buried craters:
	Looks OK, but boundary change would remove one large crater.
	I've found 5 craters that look buried to me. One is the largest class 3 crater in the south, two large class 4 craters near the southwest boundary, and 2 secondaries (class 4) near the northeast boundary (MRK)
	Added two back in (MRK).

- Size adjustment of large craters:
	Looks OK. Very minor size issues.

- Explaining unusual cases:
	This one is also listed in red, with comment "no shallow".

- Future actions:

- Completed actions:
	Marked some more secondary clusters/chains.
	Added some small type 4's.
	Boundary adjusted (MRK).
	Marked the 5 buried craters as "secondaries" - we should consider
using a unique color??

Last edited by MRK 12/17/2012