Regarding life on Mars (or anywhere else for that matter)

Did it not occur to anyone that maybe alien life does not need oxygen or water or suitable planetary living conditions in order to be able to live? For all we know, there may be some life organism that lives on Mercury that naturally can withstand the extreme heat and proximity of the sun, or lifeforms on other planets in our own solar system that can withstand each planet's respective harsh living conditions, but NASA and probably every other scientist out there wouldn't bother looking into that because to them, if it's not like Earth, it's not suitable for life. Scientists are so confined to the mindset of how organisms on Earth are able to live that they ignore other possibilities for life on other planets.

Has anyone else ever thought this?