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.