National Strategy for Planetary Protection
astrobiology.com
astrobiology.com
There is no requirement for similarity or sameness. Even if there aren't any that I know of that violate this - it's not in the definition that prions require contact with either the same or extremely similar proteins to have any affect.
Obviously, the dangers of runaway self-replication makes even the smallest samples of primitive life potentially more deadly. And, while primitive life is far more likely in the universe at large, it is astronomically unlikely to reach our solar system undirected.
> Planetary protection against "backward contamination" ensures that the Earth's biosphere is not adversely affected by the return of potentially hazardous microbes.
Interesting implications no?
Here's a direct link to the PDF.
https://www.whitehouse.gov/wp-content/uploads/2020/12/Nation...
Source: Covid-19