Interplanetary contamination

Interplanetary contamination is when something from one planet ends up on another planet. This could happen in different ways. For example, when a big rock hits a planet, some of the stuff from that planet could get stuck to the rock and get sent flying out into space, eventually landing on another planet. Another way, is when we launch rockets from our planet, it could accidentally bring some stuff from Earth with it, contaminating the new planet with things from Earth.