The earliest period of the Mercurial geologic timescale, lasting from 4568–3900 Ma ago. It marks the formation of the planet Mercury and the late heavy bombardment.
科学参考收录了60776条科技类词条，基本涵盖了常见科技类参考文献及英语词汇的翻译，是科学学习和研究的有利工具。