Mars Orbit Anomaly of Interstellar Object 3I/ATLAS between 9 October and 25 November 2025

Abstract: Interstellar cometary object 3I/ATLAS moved into the inner solar system where, after a planetary
passage near Mars at a distance of 0.193 AU, it had two distinct approaches to the Martian osculating
orbit on the 9 October 2025 and the 25 November 2025, with distances 0.129 AU and 0.018 AU, respec-
tively. Here, by analyzing JPL/Horizons astrometric data, it is shown that between these two dates
3I/ATLAS was on an anomalous trajectory with exceptional proximity, radial speed, and alignment
to the planetary orbit of Mars. Conditional on the 9th October passage, these data consistently result
in a probability of less than 2 in a million that 3I/ATLAS was on a random course from an isotropic
distribution before the tight orbital approach at 0.018 AU. This estimate suggests a recurrence time of
interstellar objects with a comparable Mars orbit anomaly of the order of 100 million years, and that the 
timing of 3I/ATLAS discovery might not had been accidental.

Keywords: Interstellar objects (52) — Exocomets (2368) — Comet dynamics (2213)

Note: Data files and program code referenced in article file are deposited at 10.5281/zenodo.17924213.