It is shown that the Earth is a natural collector of extraterrestial nonsterile artefacts that could impact our planet. Artefacts from 1.2*10 6 nearby stars could have reached the Earth over its history, and could be agents for spontaneous interstellar panspermia, even if alien civilizations pollute space only at the current terrestrial rate. ... There could be alien artefacts on the Earth even in the absence of alien expeditions to the Earth, or of interstellar missions at all. ...