Science. 1972 May 26;176(4037):909-11. doi: 10.1126/science.176.4037.909.
Tracks attributed to the spontaneous fission of plutonium-244 and of uranium-238 were detected in a large whitlockite crystal in the lunar breccia 14321 from the Fra Mauro formation. For a track-retention age of 3.95 x 10(9) years the number of plutonium tracks relative to the number of uranium tracks is 0.51 +/- 0.15, provided that the rock was not heavily neutron-irradiated 3.95 X 10(9) years ago.
在来自弗拉·毛罗地区的月壤角砾 14321 中发现的一个大型白铅矿晶体中，探测到了源于钚-244 和铀-238 的自发裂变径迹。如果岩石在 3.95 x 10(9)年前没有受到严重的中子辐照，那么相对于铀径迹，钚径迹的保留年龄为 3.95 x 10(9)年，其数量为 0.51 +/- 0.15。
