Recently, NASA astronomers have confirmed the detection of water’s chemical fingerprint on the interstellar comet 3I/ATLAS.

About Interstellar Comet 3I/ATLAS

Comet 3I/ATLAS is the third confirmed object discovered to have originated from beyond our solar system, offering scientists a rare opportunity to study ancient material from another star system. It is currently in the constellation of Virgo and has recently passed behind the Sun from Earth's perspective. 

Key Characteristics

• Origin and Trajectory: 3I/ATLAS formed in another star system, possibly in the Milky Way's thick disk, and was ejected into interstellar space billions of years ago. It is traveling on a hyperbolic trajectory, meaning it is not gravitationally bound to our Sun and will permanently leave the solar system after its brief passage. It is traveling at a very high speed, up to 68 km/s at perihelion.
• Discovery: It was discovered on July 1, 2025, by the NASA-funded Asteroid Terrestrial-impact Last Alert System (ATLAS) telescope in Chile. The "3I" in its name means the third "interstellar" object identified.
• Size and Structure: The comet has a solid, icy nucleus with an estimated diameter between 0.44 km and 5.6 km. As it approaches the Sun, it has developed a coma (a cloud of gas and dust) and a tail, which have been observed by telescopes like Hubble and the James Webb Space Telescope.
• Composition: Observations have revealed an unusual composition, including large amounts of carbon dioxide (CO₂) and atomic nickel vapor, but with minimal iron. NASA's Swift Observatory also detected hydroxyl (OH) gas, confirming the presence of water activity even at a great distance from the Sun.
• Age: The comet is estimated to be very old, potentially over seven billion years, making it older than our 4.6 billion-year-old solar system and possibly the oldest comet ever observed. 

 Current Status and Observability

• Closest Approach to Sun: 3I/ATLAS reached its closest point to the Sun (perihelion) on October 29/30, 2025, at a distance of about 1.36 AU (Astronomical Units), just inside the orbit of Mars.
• Visibility: The comet is currently (as of early November 2025) in solar conjunction, hidden behind the Sun's glare from Earth's perspective. It is expected to reappear and become observable again to large ground-based telescopes by early December 2025. It will not be visible to the naked eye.
• Closest Approach to Earth: Its closest approach to Earth will be on December 19, 2025, at a very safe distance of approximately 1.8 AU (about 270 million kilometers or 167 million miles).
• No Threat: 3I/ATLAS poses no threat to Earth.
• Future Journey: After passing the Sun, it will pass Jupiter in March 2026 on its way out of the solar system, never to return. NASA and ESA spacecraft, including those at Mars and the Juice mission, are being used to gather data during its passage. 
• The study of 3I/ATLAS offers unique insights into the chemistry and planet-forming processes of distant star systems, providing valuable comparative data to our own solar system's formation. 

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