Astrophysicists are engaged in a significant race to study a remarkable interstellar comet known as 3I/ATLAS. This unique comet entered our solar system and recently passed Mars, generating considerable excitement among scientists and space agencies alike. Although it poses no danger to Earth, its arrival marks an important event in the study of celestial bodies from outside our solar system.
What is 3I/ATLAS?
3I/ATLAS is the third interstellar object ever recorded in the solar system. It is a comet composed of ice, dust, and gas, seen as remnants from the solar system’s formation around 4.6 billion years ago. The discovery was made by Larry Dennau, part of the Asteroid Terrestrial-impact Last Alert System (ATLAS), from Rio Hurtado, Chile, in July 2025. ATLAS operates under NASA’s funding and involves researchers from the University of Hawaii’s Institute for Astronomy.
Historical Context of Interstellar Comets
- 1I/’Oumuamua: Discovered in October 2017 by Robert Weryk, this rocky object was identified using the Pan-STARRS telescope in Hawaii.
- 2I/Borisov: A rogue comet found in August 2019 by Gennadiy Borisov at the MARGO Observatory in Crimea, capable of freely traveling through space.
Current Trajectory of 3I/ATLAS
3I/ATLAS zipped past Mars in early October 2025, coming within 29 million kilometers (about 18 million miles) at a remarkable speed of 310,000 km/h (193,000 mph). It is set to make its closest approach to the Sun at the end of October, with an anticipated near pass by Earth in December. During this flyby, it will be approximately 270 million kilometers (170 million miles) away, still further than the Sun’s average distance of 150 million kilometers (93 million miles).
Research and Tracking Efforts
Various spacecraft are currently monitoring 3I/ATLAS, especially as it is temporarily obscured by the Sun. By early December 2025, the comet should reappear from behind the Sun’s glare. NASA and its partners are eager to learn more about the comet’s physical properties and size.
Tracking Missions Involved
- The Hubble Space Telescope
- The Perseverance Mars Rover
- The Curiosity Mars Rover
- The Mars Reconnaissance Orbiter
- The Europa Clipper mission (launched October 14, 2024)
- The Lucy mission and Psyche mission
- The Parker Solar Probe (launched in 2018)
- The PUNCH mission, which launches in March 2025
- The Solar and Heliospheric Observatory (SOHO)
- The ESA’s Juice spacecraft (launched in 2023)
Initial Findings on 3I/ATLAS
Researchers have acquired sufficient images to confirm 3I/ATLAS is indeed a comet. Its hyperbolic orbital path suggests it does not follow a closed trajectory around the Sun. Initial observations from the Hubble Space Telescope indicated a teardrop-shaped dust cocoon surrounding the comet’s icy nucleus, estimated to be no larger than 5.6 kilometers (3.5 miles) wide. Some calculations suggest it could be as small as 440 meters (1,444 feet) across.
The comet’s coma, a fuzzy halo surrounding the nucleus, is rich in carbon dioxide, indicating its formation in a cold environment far from its star. This has piqued the interest of planetary scientists keen on understanding its origins and implications for celestial studies.
