In this episode of Squaring the Circle, Randall Carlson provides an update on 3I/ATLAS, the third confirmed interstellar object to enter our solar system. Since its discovery in July 2025, new data from the James Webb Space Telescope and the SphereX mission have revealed that 3I/ATLAS possesses an unusually large CO₂-dominated coma, stretching hundreds of thousands of kilometers across -- nearly the size of the Earth-Moon distance.
Randall and John Arthur explore how this discovery changes our understanding of the object's composition, chemistry, and origins. They discuss the unusually high CO₂-to-water ratio (8:1) compared to comets in our solar system, what this anomaly suggests about its formation in another stellar system, and how its trajectory compares to earlier interstellar visitors like ʻOumuamua and Borisov. The conversation also considers theories about its origin, its rapid speed through the solar system, and what future interstellar objects might reveal.
This update highlights the importance of interstellar comets for understanding not only our solar system, but also the broader processes shaping planetary systems across the galaxy.