The rings of Saturn are made of ice. Earth is making rings out of space junk. Some comes back down, recently two large hunks, one “bus sized” from NASA, another, also large, from the German Space Agency and named Rosat. But not all space junk falls to earth. Some escapes into deep space to travel for eons, eventually to be captured by an advanced space-dwelling life form.
Space junk can be as simple, as an “elbow,” the kind plumbers use to connect pipes. Every space vehicle needs pipes, and space elbows will be made of advanced alloys, like molybdenum austenitic stainless steel, which those far future space-dwelles will realize came from beings with advanced technology. They will handle it carefully as they study it to learn something about us.
If this space elbow had come out of a space vehicle for human beings, and if it had been part of its sanitary system, the space beings will recognize a fragment of DNA. Et voila! They will isolate it, and with their advanced science, coax it to replicate itself.
Chances are it’s bacterial DNA, but the space beings are overjoyed to have it, and before long figure out what planetary conditions it came from, and in their quantum computers have a catalog of trillions of planets. They extract a list of those with no life of their own, and on which this ancient DNA can thrive, take it to that planet, inject it into the atmosphere and oceans, and go away, leaving an observer who spins down once in a while, takes pictures, sends them to the space-dwelling scientists who tend the progress of their many plametary implants.
For millions of years they observe this DNA as it evolves, to form single celled, then many-celled creatures, then complex life forms, and one day intelligent life that launches itself into Space and begins to surround its own planet with space junk. And that may just be how we, Humano Sapiens, on our Earth, revolving around our sun, Old Sol, came to be.