Trevor Paglen speculates:
Humanity’s longest lasting remnants are found among the stars. Over the last fifty years, hundreds of satellites have been launched into geosynchronous orbits, forming a ring of machines 36,000 kilometers from earth. Thousands of times further away than most other satellites, geostationary spacecraft remain locked as man-made moons in perpetual orbit long after their operational lifetimes. Geosynchronous spacecraft will be among civilization’s most enduring remnants, quietly circling earth until the earth is no more.
That is via Kottke.