not sure与not clear

问题描述:

not sure与not clear
not clear与not sure 有什么不同啊?it's clear 与it's sure呢?
另外,这句话里为什么要用another而不用one呢?
The pictures were of people who were so thin that they looked like beings from another planet.
那句话我现在明白了,可是前面两个词的辨析还是不太清楚,

not clear, 不清楚,不清晰
not sure, 不明确,不确定.意思差别不少呀.
地球是星球,而他们那么THIN,看起来来自其他、另一个星球,用Another,比地球以外的.用ONE不对.