Humanity has left significant amounts of junk floating in Earth's orbit since it began to explore space. However, astrophysicists from the Canary Islands Institute of Astrophysics have found something positive about it — it is an indication that a lifeform intelligent enough to at least launch satellites inhabits the planet.
This means that if we can see similar "space trash" orbiting some distant planet, it may be a pretty powerful clue that the planet is also inhabited with intelligent lifeforms, or at least has been at some point.
Skeptics, however, point out a significant flaw in the theory — from distances that far away, natural planetary satellites, like small moons or asteroid rings, may very well resemble space junk left by an advanced civilization during its conquest of space. Professor Hector Socas-Navarro from the Canary Islands Institute of Astrophysics discarded the criticism by noting that an artificial satellite can be mistaken for natural one, and that while looking for the latter you may by chance find the former.