The Uncommon Descent blog has some pull quotes from an article from the Technology Review/Physics Archiv blog entitled, The Amazing Trajectories of Life-Bearing Meteorites from Earth that make that point.
This is the idea that, when earth was struck by space objects in the distant past (e.g., asteroids), material from earth was ejected up into space from the impact, and that material held living organisms. The material was then drawn out into space by various forces. The implication is that if some of that debris made it to various moons or back to earth and was discovered today, it might mistakenly be interpreted as ET life, but it actually originated on earth.
As the Uncommon Descent link notes, astronomer Hugh Ross has been saying this for many years. I recall it from the God, Man, and ET Conference where we were both speakers, as well as some of his radio appearances. But I’d never seen (probably because I never felt compelled enough to look) any journal literature on it. Very interesting.