Overview

• 3I/ATLAS, only the third confirmed interstellar object, is on an inbound path that takes it past Mars next month before its closest approach to Earth occurs behind the Sun.
• Observations will be constrained during the Sun passage, with scientists targeting pre‑ and post‑perihelion windows to track activity and refine properties.
• Rubin Observatory imaged 3I/ATLAS during commissioning and has already cataloged more than 2,100 new asteroids, underscoring its capability to catch faint, fast movers.
• Projected discovery rates for interstellar objects with Rubin vary widely, from about one per year to as many as 70 annually, reflecting large uncertainties in the underlying population.
• Harvard’s Avi Loeb argues the object could exceed 3 miles across and 33 billion tons and urges a Mars‑orbiter HiRISE check to constrain its size, while observations indicate an active, CO2‑rich comet.