Non-sexual and Non-pornographic stories that involve purity and cuteness with same sex characters. While the characters may express their love for each other with kisses and hugs, the acts never become sexual and remain innocent. Stories of best friends who are close enough where they hug and kiss, but are not explicitly homosexual or in a romantic relationship can count as cherry.

The safeguarding of Earth and other worlds from biological cross-contamination (i.e. billionaires with too much time on their hands).

Also known as “planetary protection.” Planetary protection / quarantine “reflects both the unknown nature of the space environment and the desire of the scientific community to preserve the pristine nature of celestial bodies until they can be studied in detail.”

There are two types of interplanetary contamination. Forward contamination is the transfer of viable organisms from Earth to another celestial body. Back contamination is the transfer of extraterrestrial organisms, if such exist, back to the Earth's biosphere.