NASA’s SPHEREx Mission Detects Organic Molecules in Interstellar Comet 3I/ATLAS
NASA’s SPHEREx mission has confirmed the presence of complex organic molecules in interstellar comet 3I/ATLAS, offering valuable insights into the building blocks of life and the composition of objects originating outside our solar system. The findings, obtained through infrared observations in December 2025, come shortly after the comet became visible again from behind the Sun.
Third Confirmed Interstellar Object
3I/ATLAS is only the third interstellar object detected within our solar system, following the discoveries of ʻOumuamua and 2I/Borisov. First spotted in July 2025 by the ATLAS monitoring system, the comet follows a hyperbolic trajectory, indicating it will not remain in our solar system and will return to interstellar space. NASA scientists recognize this as a limited opportunity to study its characteristics.
Increased Activity After Closest Approach to the Sun
Comet 3I/ATLAS reached its closest point to the Sun (perihelion) in October 2025, at approximately 1.4 astronomical units. This proximity triggered significant activity, including bursts of gas and dust from its surface. Subsequent observations in December revealed a substantial increase in brightness, as material ejected from the comet’s nucleus formed a coma – a glowing envelope of gas extending hundreds of thousands of kilometers. In some instances, the carbon dioxide envelope exceeded 348,000 kilometers. NASA’s SPHEREx observed this phenomenon.
SPHEREx’s Unique Capabilities
NASA’s SPHEREx (Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer) is uniquely equipped to study such events. The telescope can observe the sky in 102 different colors of infrared light, providing detailed information about the composition of cosmic features, including cometary comas. Universe Today reports that this allows scientists to understand the materials within 3I/ATLAS and how its ices react to the Sun’s heat.
Detection of Organic Molecules
SPHEREx detected water vapor, carbon dioxide, dust, and complex organic molecules within the comet’s coma. These organic molecules, including methanol, cyanide, and methane, are complex carbon chains similar to those considered precursors to life. NASA scientists note that whereas these molecules are fundamental to biological processes on Earth, they can also be created through non-biological means.
A Window into Ancient Materials
The detected organic material has been frozen in the interstellar environment for billions of years. As comets approach the Sun, the heat causes these elements to sublimate, offering scientists a rare opportunity to study them directly. Comparisons with comets originating within our solar system suggest that interstellar objects like 3I/ATLAS have a more primitive composition.
Future Research
The data collected by SPHEREx is freely available to scientists and the public, fostering further research into the origins of interstellar objects and the potential for life beyond Earth. NASA continues to analyze the data, seeking to unravel the mysteries of these fascinating visitors from other star systems.