ex.o.sphere
n.（名词）The outermost region of a planet`s atmosphere.外大气圈：行星大气层的最外部The outermost layer of Earth`s atmosphere, lying above the thermosphere and extending thousands of kilometers into space, from which molecules having sufficient velocity can escape Earth`s gravitation.外逸层：地球大气层的最外圈，位于热层之上，并向太空延展几千公里，在那里分子具有足够的速度可以逃出地球的吸引力
【引伸】
ex.ospher.ic
