Has Alien Life Been Found in Earth's Atmosphere?

Unlike the bad astronomy blog

I'm going to go with yes. The main arguments against Wickramasinghe's panspermia related "science", "research" and "discoveries" are essentially that the detection of alien life in various papers submitted to the Journal of Cosmology are "false positives". This assumes "a priori" that alien life is very rare (almost certainly non-existent), and Earthly life is extremely flexible at getting anywhere it wants to, including into the Stratosphere at any time. Thus, the statistical calculations to work out a false positive depend on how prevalent alien life is in the first place. I don't think it is helpful for NASA to collect dust from the Stratosphere, and assume that if there is life that also exists on Earth, that it must have come from Earth. Don't bother - just go to planets, asteroids and comets and bring back samples. Otherwise you just can never rule out contamination.