We know that to a depth of about a hundred miles the mantle consists predominantly of a type of rock known as peridotite, but what fills the space beyond is uncertain.

我们知道，到了大约150公里深处，地幔主要是由一种名叫橄榄石组成，但以下2650公里是什么就清楚。

Its mission is to analyse the composition of olivine  rocks near the Shioli Crater, some 200 miles south of the Sea of Tranquility, where  Neil Armstrong took his famous " small step" .

其任务是对南部约200英里处Shioli陨石坑附近橄榄进行成分分析，这一地点正是尼尔·阿姆斯特朗迈出其着名“一小步”地方。

The mantle contains rocks called peridotite.

地幔含有称为橄榄石。