Interstellar Comet 3I/ATLAS Makes Closest Earth Pass Today at 270 Million Km

Overview

• The object is only the third confirmed interstellar visitor, discovered by the ATLAS survey in Chile in July 2025.
• Closest approach occurs around 19 December at roughly 270 million kilometers, too faint for naked-eye viewing and posing no impact risk.
• Coordinated campaigns with JWST, ESO's Very Large Telescope and Mars-orbiting spacecraft are producing images and spectra, with many findings posted as preprints.
• Early analyses indicate atypical chemistry, including CO2 richness and a higher nickel fraction than seen in most Solar System comets, though key parameters remain under study.
• The comet showed an early inverted tail likely tied to asymmetric sublimation and large grains, and scientists characterize it as a natural comet that will depart the Solar System.