Comet 3I/ATLAS: An Interstellar Visitor Approaches Mars
RÍO HURTADO, Chile — Comet 3I/ATLAS, discovered on July 1, 2025, by an Asteroid Terrestrial-impact Last Alert System (ATLAS) telescope, is set to make a significant pass close to Mars in early October 2025 as it travels through the Solar System.
The comet is currently positioned on the far side of the Sun, obscuring it from Earth-based observations. To maximize the scientific opportunity, the European Space Agency (ESA) has coordinated efforts with its Mars orbiters, including the Mars Express and the ExoMars Trace Gas Orbiter, to observe 3I/ATLAS as it approaches the Red Planet.
On October 3, the spacecraft will be about 30 million kilometers from the comet, allowing for enhanced observations that could yield valuable data on the comet’s structure and activity. Following this, from November 2 to November 25, ESA’s Jupiter Icy Moons Explorer (JUICE) will begin its observations of the comet during its closest approach to the Sun.
Dr. Bryce Bolin, a research scientist, emphasizes that studying 3I/ATLAS could provide insights regarding the early solar system and the formation of planetary systems beyond our own. This comet is particularly interesting because it exhibits signs that suggest it has been active, featuring a bright halo and a long tail.
In line with predictions, 3I/ATLAS is expected to remain visible until late October before it goes behind the Sun, re-emerging in late November. Observations suggest that it might become one of the brightest interstellar objects documented, reaching a magnitude detectable with telescopes.
The trajectory of 3I/ATLAS is hyperbolic, indicating that it is an interstellar visitor, and analysis shows that it is likely over 7 billion years old, making it possibly older than our Solar System. Its composition, containing water and carbon dioxide, is similar to that found in local comets, which highlights a shared chemistry among celestial bodies across the galaxy.
A significant solar event, a coronal mass ejection (CME), is expected to collide with the comet during its passage, providing an opportunity for astronomers to study how this interaction affects the comet’s tail and activity.
As observations ramp up, the scientific community is eager to analyze how this ancient traveler behaves as it nears the Sun. Future studies could help reveal more about the early solar system and the variety among interstellar objects.
