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Mars Orbiters Capture Closest Views of Interstellar 3I/ATLAS as UV Data Reveal Intense Water Outgassing

Forthcoming perihelion observations, including ESA's JUICE campaign, are expected to clarify its origin.

Overview

  • ESA’s ExoMars Trace Gas Orbiter and NASA’s Perseverance obtained the nearest images to date around the Oct. 3 Mars close pass, revealing a distinct coma but no resolved nucleus and no tail in TGO frames.
  • NASA’s Swift observatory detected hydroxyl in ultraviolet light, indicating roughly 40 kilograms of water per second venting when the object was about 2.9 AU from the Sun.
  • Major agencies describe 3I/ATLAS as a likely natural comet and say it poses no danger, with its trajectory keeping it at least about 170 million miles from Earth.
  • Harvard’s Avi Loeb publicized a higher mass estimate (over 33 billion tons) and a 30–40% probability of a non‑natural origin, claims that remain disputed by many researchers and are not agency consensus.
  • Key observing windows approach: perihelion is late October, ESA’s JUICE will monitor the object in November, and additional spacecraft campaigns near Jupiter are planned for March 2026.