Even authoritative sources published online occasionally slip, and use of it’s when they really mean its. The reverse mistake rarely occurs – that is, preferring its to it’s.
This preference for it’s in online ephemera is not such a bad thing – consider that when say something about it – its is actually a contraction of it’s.
So grammatically, its and it’s are not that distant.
But in academic publications – be clear what you are saying:
There, it’s means It is – and its cannot be the subject of a sentence since it is (or it’s) a pronoun whose contracted apostrophe and s give it the meaning “of it.”