Mezentsev

D=85 km
Center: 72¡N, 230¡E

Count Area: 2077 km^2
Observed Density (@ 1km): 23100 ± 3400
Age: [3.8 ± 0.1 (+sec: 4.0)]
Stoffler epoch: [Pre-Nectarian]
Fit density (@ 1km): [18100 ± 5900]
PF fit: poor, mid and large craters shallow, and have to remove 8 of largest craters to get decent fit

Age calculation notes:
- poor fit - anchored at intermediate D. Fit not improved using Hausen and Holsapple scaling law or layering (SM).
- bad fit - large D almost within error - small much shallower - possibly geology - but try strength; adding OSs does not change fit or age. Because using strength or layer does not improve fit and fit is bad, it is unlikely we can report a good age for this surface. Geology may be a strong candidate - walls are very subdued indicating burial and collapse - surrounded by several younger craters - one large fresh crater on floor - although not in counting area there are some large craters in clusters nearby. (MRK)

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

Wilhelms: 
Pre-Nectarian? (all materials)

Floor material: 
Best guess is not original. Relatively flat floor, crater wall shorter than expected, No central peak. Material looks softened. Loose?

Geology Observations: 
Ejecta blanket not visible. Rim is heavily eroded. No central peak. Floor relatively smooth, but does have a "textured" look to it. A few secondary chains/clusters with largish craters (up to ~ 3 km) of various degradation states. Small fresh secondaries too.

SFD Observations: 
SFD is shallow over all diameters. Perhaps the production of several large craters (including the recent one in the north), including large secondaries, has "temporarily" reset the smallest craters? Craters < ~ 3 km dominated by class 3 and 4, larger craters are fresher. Slope(Diff)= 2.3 ± 0.2.

Discussion notes: 
change boundary to exclude large crater and its ejecta (did not help)

Notes from Brian's adjustment:
- Counting boundary:
	Boundary extends onto crater wall in several places.
	Agree. (MRK)
	Boundary changed to exclude large crater and its ejecta blanket (MRK).

- Secondaries:
	Pretty good.
	Maybe some small, fresh ones in center. (MRK)
	Suspicious about 3 larger craters just to northwest of center? (MRK)

- Removal of large, buried craters:
	Adjusting the boundary line will remove some fairly large craters.

- Size adjustment of large craters:
	Several large craters are close but should be tweaked.
	I'm concerned about a few of the classifications of larger craters. (MRK)

- Explaining unusual cases:
	Listed in red with comment "no shallow".

- Future actions:

- Completed actions:
	Fixed size of three large craters (BLE).
	Added a few type 4's - minor (BLE).
	Adjusted boundary (MRK).
	Added some secondaries (BLE).

Last edited by MRK 12/14/2012