Two good reasons to question the claim that alien life has been found in Earth's atmosphere
First, neither the authors of the paper, nor the journal its published in, have the best track record for careful work, well-documented research, or non-hyperbolic results. More important, the actual paper, itself, makes claims it can't back up
. Case in point, says Phil Plait, the alien in question is a particle the authors assume is part of a diatom — a single-celled plant. The paper actually says "assume", and, from the sounds of things, they haven't even checked out that basic, important idea with a diatom expert.