We don't know just how thick it is, probably miles thick, so it's very expensive and very difficult to go down there -- send down your submarine or whatever it is -- and explore.
我们甚至连其厚度也不知道 也许有几英里厚 要去到冰层之下 需要花费大笔的钱 克服重重困难 才能让潜艇下水 进行探测