This is a real zinger...
In 2000, a group based in the Cardiff Centre for Astrobiology in Wales declared they had found alien microbes in a Leonid fireball based on an infrared spectra of the organic material. Skeptic Matt Genge had this to say:
The infrared spectra of the Leonid meteors are not evidence for bacteria, nor
are the infrared spectra of comets," Genge said. He added that the data show a
feature that is common in all organic material.
"If you took me, put me in an oven, dried me at 300 degrees and then took my
infrared spectra, I'd have [this feature] too. This would certainly not be
evidence that you'll find Matt Genges on comets.