Interstellar Object 3I/Atlas Passed Mars Last Night
a day ago
- #astronomy
- #space-exploration
- #interstellar-object
- 3I/ATLAS, the 3rd known interstellar object, made its closest approach to Mars on October 3, 2025, at 18 million miles (29 million kilometers) away.
- Multiple space agencies, including NASA and ESA, coordinated observations using Mars orbiters like Mars Express, ExoMars Trace Gas Orbiter, and Mars Reconnaissance Orbiter.
- 3I/ATLAS will reach perihelion (closest point to the sun) on October 29, 2025, at 1.36 AU, just inside Mars' orbit.
- The object is not visible to the unaided eye but can be observed with 8-inch or larger telescopes, with the best viewing opportunity in November.
- ESA's Jupiter Icy Moons Explorer (Juice) will observe 3I/ATLAS between November 2-25, 2025, capturing its active state post-sun approach.
- Originating from the Sagittarius direction, 3I/ATLAS's home star system remains unidentified despite extensive research tracing its path back 10 million years.
- Researchers used Gaia data to analyze 93 star encounters but found none significantly altered 3I/ATLAS's trajectory.
- The object likely originated from the Milky Way's thin disk, possibly ejected from an early-formed planetary system.
- 3I/ATLAS is considered a key probe for studying icy planetesimals and galactic planet formation processes.
- Size estimates for 3I/ATLAS's nucleus have decreased from 12 miles (20 km) to as small as 1,050 feet (320 meters).
- Previous interstellar objects include 1I/'Oumuamua and 2I/Borisov, with 3I/ATLAS being the fastest at 130,000 mph (210,000 kph).
- Discovered by ATLAS on July 1, 2025, its interstellar nature was confirmed the next day, and Hubble imaged it on July 21, 2025.
- No dedicated spacecraft mission is planned for 3I/ATLAS, but ESA's future Comet Interceptor aims to study similar objects.