Earth Planets Space, Vol. 60 (No. 4), pp. 265-270, 2008
Tomokatsu Morota1, Jun'ichi Haruyama1, Chikatoshi Honda1, Yasuhiro Yokota1, Makiko Ohtake1, Yoshiko Ogawa2, and Tsuneo Matsunaga2
1Institute of Space & Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Sagamihara 229-8510, Japan
2Center for Global Environmental Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba 305-8506, Japan
(Received March 30, 2007; Revised August 9, 2007; Accepted October 31, 2007; Online published April 9, 2008)
The crater frequency is often used to determine ages of planetary surfaces. In this study, we evaluate the statistical fluctuation of the crater frequency and its effect on age determination using a Monte Carlo simulation prior to the SELENE (KAGUYA) / Terrain Camera acquiring extensive high-resolution images over the entire Moon. We found that the ages estimated between 2.5 and 3.5 Gyr tend to be too young when there are not enough craters. Age determination for Eratosthenian units is least accurate. The errors defined with 1σ are 0.7 Gyr for units of 100 km2, 0.5 Gyr for units of 1000 km2, and 0.4 Gyr for units of 2500 km2. The maximum error exceeds 20% and is comparable with the error due to the cratering asymmetry.
Key words: Moon, cratering chronology, crater size-frequency distribution, statistical fluctuation.