Ever heard a science fiction story about the life of a "planetary protection officer"? Me neither. Buckle up though people, because this is exactly what some of the world's premiere space agencies have in the pipeline.
NASA and the European Space Agency are both looking to hire full-time planetary protection officers. Their role? To prevent the contamination of Earth by alien forces, and to stop Earth from contaminating other planets. Now I know all your minds are jumping to legendary alien killers from Hollywood; Han Solo in Star Wars, and Will Smith in Independence Day - but unlike Will Smith, this officer will be more environmentalist than alien-punching badass.
Alien contamination is less a matter of world-busting, soul-harvesting and galaxy-conquering, and more about germs in a Petri dish. It's easy to get carried away with imaginations of intergalactic slaughter, but what 'contamination' really means is infecting a pristine alien environment through human presence.
A good example of this is a probe called the Cassini-Hyugens. The Cassini has been orbiting Saturn since 2004, and recently came into contact with an underwater ocean on the surface of one of Saturn's moons. Enceladus, the oceanic moon, is covered in cryovolcanoes, which are essentially water volcanoes that launch saltwater from beneath the moon's ice crust into outer space.
The Cassini was struck with one such plume of saltwater, and researchers immediately decided that it should be destroyed, lest it contaminate the surface of a watery moon that could contain alien life.