To start, I'm just going to say, you didn't hear this from me. If anyone at NASA is reading this, I made this entire story up so don't even worry about it. This did not happen to any of the missions I worked on... Just on one that some people I know work on.
The first thing I need to cover is that there are different levels of clean room. So a clean room is what it sounds like, a room where you don't have a bunch of dirt and crap contaminating your expensive instruments, but they range from "just put a hairnet on" to "we count the number of particles per cubic foot in the couple thousands." Which clean room you need depends on the kind of instrument you're building - magnetometers for example are pretty resistant to random skin oils or dust, whereas dust detectors are obviously highly sensible to dust.
Especially dust detectors which are on planetary missions. Where we are possibly investigating space near planets or moons or asteroids for signs of life.
My lab builds these dust detectors so we have one of these super clean rooms. One such instrument was shipped off to California for spacecraft integration by another lab. While they were doing their final tests, they found... A spiderweb. In the very expensive dust instrument. Which was supposed to be so clean from contaminants that it was only touched by people wearing 3 layers of clothing and doubled up face masks.
Big big problem. They had to do a very careful job cleaning it. And California lab actually got the spider web genetically tested because they wanted to know who had spiders in their clean room and was thus at fault (valid question, but also would make my lab look very bad!)
Results came back... California spider. Huge success! And if news comes out in the next 5-10 years that they have found signs of remarkably spider-adjacent life forms on a nearby celestial body... Take it with a grain of salt.
