Icarus

D= 94 km
Center: 6¡S, 187¡E

Count Area: 1106 km^2
Observed Density (@ 1km): 17200 ± 4000
Age: 3.8 ± 0.1 (+sec: 3.9)
Stoffler epoch: Early Imbrian
Fit Density (@ 1km): 18900 ± 2900
PF fit: good?, one small bin slightly steep, and curving for mid and large craters, also many secondaries and small count area (~ 1100 km2)

Age calculation notes:
Bad fit - much better including OSs (SM).
Fit could possibly be improved, if just try and fit small craters(?) - this is a crater with "right ear"; including OSs does improve fit for small diameters and changes age slightly - candidate for retry. Forcing fit to go through small craters does improve fit slightly (*_HN2), but does not change age much (MRK).

USGS geology: 
Crater mapped as middle Imbrian. Portions of crater floor mapped as fill with an Imbrian age - some may be original floor.

Wilhelms:
Nectarian (all materials)

Floor material: 
Best guess is not original. Very smooth flat floor around peak, edges meeting wall are sharp and look embayed, filled larger crater at 10:00. Also surrounded by a few craters filled with mare. Material looks fresh. Hard?

Geology Observations: 
Ejecta blanket somewhat eroded. Rim looks slightly eroded, but still some sharpness. Very large central peak. Portion of floor flat, but remaining is hummocky (original floor, collapse? - avoided). Several secondary chains/clusters, especially in southwest with larger craters up to ~ 1.7 km.

SFD Observations: 
Small craters (< 1.2 km) dominated by classes 3 & 4, but mid-sized craters are dominated by fresher classes. Largest are dominated by class 4. Distribution < 1.5 km steep. Slope(Diff)=5.5 ± 0.5.

Discussion notes: 
"possibly" original floor. many secondaries and small count area, not likely good for PF comparison and age

Notes from Brian's adjustment:
- Counting boundary:
	Very irregular do to a huge central peak, but looks OK.

- Secondaries:
	Many small-crater clusters are marked.

- Removal of large, buried craters:
	One large crater appears to be somewhat fresh - should be OK.
	I thought we should remove the large class 3 crater at the 10:00 position. I think we discussed this earlier. It is definitely affected by fill. (MRK)

- Size adjustment of large craters:
	Looks good.

- Explaining unusual cases:

- Future actions:
	None?

- Completed actions:
	Removed large semi-buried class 3 crater.

Last Edited by MRK 12/13/2012