Technosignatures in the Solar System

Abstract:

NASA has five robotic space probes on escape trajectories from the solar system (Pioneer 11, Pioneer 12, Voyager 1, Voyager 2, and New Horizons), and the Interstellar Probe is a concept likely to be submitted for consideration in the forthcoming Solar & Space Physics Decadal Survey. While none of these robotic probes will be operational on the time scale that it would take to reach another star, it is natural to ask whether another civilization might also be sending out interstellar probes. Serious consideration of such interstellar probes dates at least to R. Bracewell in the early 1960s, and the discovery of 1I/2017 ‘Oumuamua has rekindled some of that interest.
I consider what limits exist on signatures of extraterrestrial technology might be present in the Solar System, considering both objects on various orbits (“probes”) and surface artifacts, using data available from planetary exploration and astronomical sky surveys. Perhaps not surprisingly, the completeness to which the Solar System has been searched varies as a function of distance from the Sun. However, with notable exceptions, only extremely crude limits can be placed on the existence of interstellar probes. I also highlight areas that might be profitable for improving these limits considerably.