A few twentieths of a gram can be critical. 二十分之几克可能是关键的。
Extracting information about the large-scale composition of a planet from a sample weighing a millionth of a gram was a fascinating example of scientific endeavour. 从重量为百万分之一克的样品中提取有关行星宏观组成的信息是一个极为有趣的科学尝试实例。