Confidence level (Co) that structure is an impact crater. Possible values are 1
(almost certain, 80 to 100% confidence), 2 (probable, 30% to 80% confidence),
and 3 (cannot be ruled out as an impact structure, <30% confidence).
Confidence levels are subjective, but are generally based on the presence or
absence of such features as "hummocky" ejecta, well-defined ejecta deposits,
rough walls, terracing (larger craters only), and a central peak or peak ring
(larger craters only). Volcanic structures, the features most often confused
with impact craters, usually are steep-sided, have smooth inner walls, and have
smaller, less complete (if any) ejecta deposits than impact craters.