Kinematic and Thermodynamic Constraints on the Anomalous Acceleration of Interstellar Object 3I/ATLAS (C/2025 N1)

ABSTRACT: We present a kinematic and thermodynamic analysis of Interstellar Object 3I/ATLAS (C/2025 N1), identifying significant deviations from standard cometary behavior. The object exhibits a non-gravitational acceleration of $3 \times 10^{-10} \text{ AU/d}^2$ aligned with a persistent, 400,000 km collimated sunward jet.

Unlike typical cometary outgassing, which is driven by isotropic surface sublimation in thermal equilibrium, the ejecta from 3I/ATLAS displays a profound thermal deficit ($T_{obs} \approx 140 \text{ K}$ vs. $T_{eq} \approx 180 \text{ K}$), implying rapid adiabatic expansion through a constricted geometry. We demonstrate that the observed collimation requires an exhaust velocity $v_{ex} > 0.5 \text{ km/s}$ to overcome solar wind dynamic pressure.

Based on recent spectroscopic data indicating a 20-fold surge in post-perihelion mass loss (January 2026), we propose a "Contained Volatile" model (an ablative propulsion mechanism utilizing a monolithic pressure vessel) that challenges the standard "rubble pile" surface sublimation hypothesis.

To rigorously test this model against natural outgassing, we derive two critical, falsifiable constraints:

• Thermodynamic Discontinuity: Unlike natural comets which fade gradually (inverse-square law), we predict a "Step-Function" cessation of outgassing (a "Hard Stop") in April 2026.

• Kinematic Deviation: We predict a non-gravitational inclination change ($\Delta i$) at the Jupiter periapsis (May 2026) exceeding ballistic scattering predictions.

These predictions serve as a rigorous test to distinguish between natural cometary outgassing and active, directed propulsion mechanisms.

PUBLICATION STATUS:

• Status: Independent Pre-print (2026).

CRITICAL DISCLAIMER: This manuscript is currently an independent pre-print hosted on Zenodo and has NOT been peer-reviewed. The findings, kinematic analyses, and thermodynamic models presented herein are preliminary and subject to revision based on expert feedback. The hypothesis of an ablative propulsion mechanism remains speculative until confirmed by independent observation.