Podcast: Planetary Protection Protocols
By: Astronomy Cast
Based on how likely a destination is to have life on it, there are different levels of cleaning and decontamination spacecraft must undergo before being launched.
The idea is that we don’t want to carry life with us that could potentially be an invasive species on a different planet and destroy or otherwise negatively impact native life.
When the protocols were first written up, we weren’t aware of the potential for life on many places we now think it could reside, such as Titan, Ceres, or even the gas giant planets.
Also, the methods used to clean some of the earlier Mars missions such as Viking I and II would not have necessarily have killed some of the extremophile life we now know exists.
Tardigrades are awesome.