Interstellar Comet 3I/ATLAS Dazzles with Explosive Jet Activity

A remarkable interstellar comet, known as 3I/ATLAS, is currently traversing our solar system and captivating astronomers with its spectacular jet blasts and vibrant gas clouds. This celestial object, originating from beyond our solar system, is providing scientists a unique opportunity to analyze materials from a distant region of the galaxy. With its unusual chemical signature, 3I/ATLAS challenges existing theories regarding the building blocks of planets.

On July 21, 2025, the Hubble Space Telescope captured images revealing a teardrop-shaped dust cocoon enveloping a solid icy nucleus, a defining characteristic of comets. Follow-up observations indicated that the nucleus measures between 440 metres and 5.6 kilometres in diameter. Its size, combined with its interstellar origins, makes 3I/ATLAS an invaluable sample of ancient cosmic material.

The excitement surrounding this comet intensified with observations from the James Webb Space Telescope in August 2025. Scientists discovered that the gas cloud encircling the comet is predominantly composed of carbon dioxide (CO2), with a CO2-to-water ratio of approximately 8:1, one of the highest ever recorded for a comet. Additionally, the comet features water ice, water vapour, and carbon monoxide (CO).

Further analysis from ground-based telescopes revealed a weak emission of cyanide (CN) and a significant depletion of carbon-chain molecules compared to typical solar system comets. These peculiarities suggest that the nucleus of 3I/ATLAS has undergone intense cosmic-ray exposure over billions of years, supporting theories of its deep interstellar origin.

As the comet continues its journey, various NASA and European Space Agency (ESA) probes, including the Lucy Spacecraft, MAVEN, and the Mars Reconnaissance Orbiter (MRO), have been collecting and sharing data. In October 2025, 3I/ATLAS made its closest approach to Mars at a distance of roughly 30 million kilometres, allowing orbiters to capture ultraviolet images of its coma.

NASA organized a livestreamed event on November 19, 2025, to present data collected from these observations, a release that faced delays due to a US government shutdown. Unlike comets formed within our solar system, which reflect the chemical environment of the early Sun, 3I/ATLAS offers insights into the composition of a foreign star system. Its high CO2 content and depleted carbon chains hint at formative conditions distinct from those experienced in our solar system.

According to a statement from NASA, all current observations affirm that 3I/ATLAS is indeed a comet, not an extraterrestrial spacecraft, but one of immense scientific importance. Amit Kshatriya, a NASA scientist, remarked, “It looks and behaves like a comet … but this one came from outside our solar system, which makes it fascinating, exciting, and scientifically very important.”

Looking ahead, 3I/ATLAS is expected to make its closest approach to Earth on December 19, 2025, at a distance of about 270 million kilometres (approximately 170 million miles). While this distance is considered safe, it will allow ground-based and space telescopes to continue gathering valuable data as the comet heads back into interstellar space.