The journal of Cosmology is regarded as a low-quality publication by many scientists. I can't judge the assertions in the paper but the methodology seems good.
What flags this for me is that if you have an organism in hand, it's easy to do more analysis to provide evidence that it is not terrestrial. At the moment, I'd still say that the hypotheses of "their probes was contaminated", "our model of what particles are in the stratosphere are wrong and this is fully terrestrial life", and "they're flat-out lying" remain higher odds based on this evidence than "they found extraterrestrial life". In our own atmosphere.
They even mention a test they could run, but they did not wait to run the test before announcing. Not a good sign. Especially since that is not a lengthy test to run, compared to the speed of publication....
I of course reserve the right to change my mind based on more evidence; I have no problem with the idea that our stratosphere models may be wrong, for instance, and if extraterrestrial really is raining down on our stratosphere, so be it. Let facts be the judge. But some sort of biochemical or isotope evidence this is not just another extremophile would be nice.
I would buy the stratospheric model being wrong, but assuming good faith I think they've addressed the contamination objection - you'll note that they did a control with the same procedures except for opening the sample drawer and it came back clean. This is highly reproducible so I'm going to assume they're reporting in good faith.
Flat-out lying was mentioned last because I rate it the lowest. But also non-zero. This is a field that has had many more liars than discoveries, though certainly when there are zero discoveries to be made in the search space we've had access to so far that says less than it might otherwise.
Please read your link. That addresses deficiencies in a paper about a meteorite. This paper is about samples collected from a weather balloon. And while the criticisms in your link are well-founded, I feel sure you can find equally well-founded criticisms without all the distracting ad-hominem insults.
The paper contains almost no detail about the methods used, and lacks involvement of a diverse group of authors. This indicates that the authors are not thinking hard enough about alternative theories to explain what they have found.
For instance, the paper contains this sentence:
"It is also unlikely that the fragment could have come from commercial aircraft, which fly below well below our stratospheric sampling height."
Unless they have a completely sterile, sealed container that is open only at certain altitudes to collect material in a filter, they will have nothing to stand on.
NASA had a satellite that was sent up to collect samples of debris along a particular orbital belt and worked like this. They were doing tests to see how much space junk had accumulated and would open one of the compartments for a fixed period of time, then re-seal it before switching to another.
Unless they have a completely sterile, sealed container that is open only at certain altitudes to collect material in a filter, they will have nothing to stand on.
That is exactly their claim (with detailed method), and they did a control as well, in which the container was not opened, to validate their anti-contamination protocols. I'm all for critiques of the paper, but I do think you might have gone to the bother of looking at it first.
They even mention a test they could run, but they did not wait to run the test before announcing. Not a good sign. Especially since that is not a lengthy test to run, compared to the speed of publication....
I of course reserve the right to change my mind based on more evidence; I have no problem with the idea that our stratosphere models may be wrong, for instance, and if extraterrestrial really is raining down on our stratosphere, so be it. Let facts be the judge. But some sort of biochemical or isotope evidence this is not just another extremophile would be nice.