Searching for Solar System Probes | Joseph Lazio | IAUS404

Technosignature Searches within the Solar System Presented by Joseph Lazio Jet Propulsion Laboratory, California Institute of Technology Presented at IAU Symposium 404: Advancing the Search for Technosignatures | 2–6 March 2026 ABSTRACT: NASA has five robotic space probes on escape trajectories from the Solar System, and the Interstellar Probe concept was considered in the recent U.S. Solar & Space Physics Decadal Survey. While none of these robotic probes will be operational when they reach another star, it is natural to ask whether another civilization also might have sent out interstellar probes. Serious consideration of such interstellar probes dates at least to R. Bracewell in the early 1960s, and the discovery of three interstellar objects has rekindled some of that interest. I consider current limits on signatures of extraterrestrial technology in the Solar System, both objects on various orbits (""probes"") and surface artifacts, using data 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 technosignatures in the Solar System. I also highlight areas that might be profitable for improving these limits considerably. KEYWORDS: interstellar probes, Bracewell probes, technosignatures in Solar System, planetary surveys, astronomical sky surveys, interstellar objects, NASA missions, alien artifacts Presented 2–6 March during Advancing the Search for Technosignatures, an online symposium from the International Astronomical Union (IAU; https://www.iau.org/) and Blue Marble Space Institute of Science (BMSIS; https://bmsis.org/).