Shayn

D=93 km
Center: 33¡N, 172¡E

Count Area: 1423 km^2
Density (@ 1km): 46400 ± 5800
Age: [4.0 ± 0.1]
Stoffler epoch: [Pre-Nectarian]
Fit density (@ 1km): [47200 ± 11000]
PF fit: poor, large craters are too shallow, and it takes 8 large craters to be "removed" to fit 

Age calculation notes:
- poor fit - anchored at large D. Using Hausen and Holsapple scaling or layering does not improve fit (SM).
- poor fit for small craters (up to 2 km) - too shallow - large craters OK - maybe geology/large number of large craters - but try strength scaling law; adding OSs degrades fit to large craters and increases age slightly. Using Hausen and Holsapple strength scaling law does not improve fit - use w/o scaling. Geology is a strong candidate - surrounded by several large fresh craters - several fresher, larger craters on floor too. (MRK)

USGS geology: 
Crater mapped as Nectarian. Most of floor material mapped as fill with Imbrian to Nectarian age. Small area of floor to south mapped as Imbrian.

Wilhelms: 
Crater is Pre-Nectarian. Perhaps filled with Nectarian aged material?

Floor material: 
Best guess is not original. Flatter floor, material has contacts with wall that look embayed, fill in larger crater on the floor, no central peak. Material looks softened. Loose?

Geology Observations: 
Ejecta not visible. Rim is eroded. No central peak. Floor mostly smooth. A few hummocky areas near wall that are likely collapses (excluded). A few secondary chains/clusters with various sized craters (up to ~ 10 km) - mostly degraded. Not completely sure about the 3 large craters to the NW being secondaries, but there are other cluster/chains around the crater that look like secondaries too.

SFD Observations: 
Craters < ~ 2 km dominated by classes 3 & 4. Largest craters dominated by class 3. Has flat SFD for full diameter range. Slope(Diff)= 2.8 ± 0.2.

Discussion notes: 
move boundary to exclude large secondaries in NE quadrant to see if improves fit (not really)

Notes from Brian's adjustment:
- Counting boundary:
	Could exclude some of the crater wall near 1:30.
	A few craters were missed, but not bad.
	Excluded area with large secondary craters (MRK).

- Secondaries:
	Note - several large craters may be in clusters but aren't marked yet.

- Removal of large, buried craters:
	If boundary changes, one buried crater might be removed.

- Size adjustment of large craters:
	One large type 4 near center should be larger.

- Explaining unusual cases:
	Shayn marked in red, with comment "no shallow".
	Lots of big craters, looks OK.

- Future actions:
	Verify the secondary clusters? (Michelle)

- Completed actions:
	Many boundary changes (Michelle).
	Fixed size of three large craters near center (BLE).
	Added some clusters (BLE).
	Marked some missing craters (BLE).
	Adjusted a few class designations and added a few craters (MRK).

Last Edited by MRK 12/17/2012