Interstellar comet 3I/ATLAS departs after brief stop in our skies

Yesterday 09:20

By: Dakir Madiha

Interstellar comet 3I/ATLAS departs after brief stop in our skies

Interstellar comet 3I/ATLAS is now racing away from the inner solar system after a fleeting but revealing visit that has given astronomers fresh insight into the chemistry of deep space. The icy body is only the third confirmed object known to have entered our planetary neighborhood from another star system, following 1I/‘Oumuamua in 2017 and 2I/Borisov in 2019. It is currently on course for a close pass by Jupiter in mid March before it heads back into interstellar space on a path it will not repeat.

The comet was first identified on July 1, 2025, by the NASA funded ATLAS survey telescope in Río Hurtado, Chile, after its unusually fast motion and hyperbolic orbit marked it as an interstellar visitor. It reached perihelion on October 29, 2025, when it passed closer to the Sun than Mars’ average orbit, and it made its closest approach to Earth on December 19 at a distance of about 170 million miles, remaining accessible only to telescopes rather than the naked eye. Astronomers quickly recognized that its brief passage offered a rare chance to sample unaltered material that likely formed around another star billions of years ago.

As 3I/ATLAS moved away from the Sun, it unexpectedly brightened and became far more active. Observations by NASA’s SPHEREx mission in December 2025 showed the comet undergoing a sharp outburst, with jets blasting dust and gas into space as solar heat penetrated through its radiation baked outer layers into pockets of fresh ice. Spectra revealed not only water vapor, carbon dioxide and carbon monoxide, but also a rich mix of organic molecules including methanol and cyanide, indicating that the nucleus preserves complex chemistry similar to or even richer than that seen in many solar system comets.

A wide range of spacecraft joined the observing campaign while the comet crossed the planetary region. NASA’s TESS satellite carried out a special observing run in January 2026, producing a long time lapse sequence that tracks the comet drifting across a crowded star field. Earlier, ESA’s ExoMars Trace Gas Orbiter and Mars Express watched 3I/ATLAS as it passed near Mars in late 2025, while NASA’s Europa Clipper secured rare ultraviolet data during a window when the comet lay too close to the Sun for ground based telescopes to observe. In February 2026, the European Space Agency released the first science camera image of the comet from its Jupiter Icy Moons Explorer mission, taken in November 2025, showing a bright coma and an extended tail shaped by multiple narrow jets and filaments.

Trajectory calculations show that 3I/ATLAS will pass about 33 million miles from Jupiter on March 16, 2026, experiencing a final gravitational nudge before it leaves the planetary region for good. The comet should remain observable in the pre dawn sky with modest amateur telescopes into the spring of 2026, fading gradually as it recedes toward the outer solar system. It is expected to cross the outer reaches of our system in the late 2020s and early 2030s on its way back to interstellar space.

Researchers are already considering how to follow this visitor long after it has disappeared from Earth’s skies. A team led by scientist Adam Hibberd has outlined a mission concept in which a spacecraft launched around 2035 would use a close solar flyby, known as a Solar Oberth maneuver, to gain enough speed to intercept 3I/ATLAS decades later. The plan would require a roughly 50 year cruise and careful alignment of Earth, Jupiter, the Sun and the comet, but it could allow a future generation to study an interstellar object up close and directly sample material that predates the birth of our own solar system.