why do you take the position that its impossible for people to do this? are you informed enough to say for sure? otherwise, its arguing out of ignorance. "I dont see how someone could do this" doesnt mean they didnt. much like the pyramids.
im behind occams saying that its more than likely people from here. to say aliens, you're already assuming they exist and that they are here, several very huge assumptions that cant be proven as far as i know.
im very skeptical of crop circles obviously. i want someone to show me non biased proof about soil compositions etc. that point to it being something supernatural/nonhuman.