Venus shows why ozone isn’t a good biosignature

> However, the existence of ozone in Venus’s observable atmosphere, a planet with no known life, raises the possibility of ozone biosignature false-positives on Venus-like exoplanets.

While the formal logic holds for arguing it isn’t a reliable biosignsture, I can’t help but feel a different informal argument is being implied that does not follow from this reasoning.

It goes something like this:

* We haven’t found life on Venus.

* We have detected ozone in the atmosphere of Venus.

* This means there **must be** an abiotic chemical pathway for making ozone in an atmosphere.

* Therefore we cannot treat ozone as a biosignature.

The issue here lies in the strength of the claim that the presence of ozone on Venus and our lack of detection of life implies the presence of an unknown chemical pathway for ozone production.

… Because it’s also possible life does exist on Venus, and our wildly inadequate sampling of its atmosphere simply hasn’t found it. 

Ironically, the article you referenced cited a paper that talks about an unexplained origin of ozone coming from the nightside of Venus, rather than some sort of photochemical origin. I.E. something that could be explained by living organisms in the atmosphere producing it at night but not during the day. 

Anyway, there’s no proof of such life existing, and our surveys of the atmosphere of Venus aren’t even remotely comprehensive enough to have strong confidence about the question either way. We’re speculating about the chemistry of something we have barely sampled. 

VATMOS-SR or a mission like it would likely be informative here. 

“I smell BBQ smoke and hear a party next door, but I have never seen anyone living there. Therefore, evidence of a cookout is an unreliable indicator of human presence.”