In July 2025, a remarkable cosmic object known as 3I/ATLAS made a rare visit to our solar system from interstellar space. This was the third known object to originate beyond our solar system, and it spent about four months in the inner solar system, passing close to the sun. Scientists are particularly interested in 3I/ATLAS because its composition may provide clues about the presence of life’s building blocks in distant star systems. Martin Cordiner, a researcher at NASA’s Goddard Space Flight Center, believes that 3I/ATLAS is likely a fragment of a planetesimal—a small, rocky body that could have been part of a larger planet in its original system. Darryl Seligman, an astronomer at Michigan State University, suggests that comets like 3I/ATLAS might have played a role in delivering carbon-based chemicals to planets, including those that could support life. These chemicals, such as methanol and amino acids, are fundamental to the formation of biomolecules, the basic components of life. Observations of 3I/ATLAS have uncovered a variety of chemicals crucial for life as we know it. Using the Atacama Large Millimeter/submillimeter Array (ALMA), scientists detected hydrogen cyanide (HCN), as well as large amounts of formaldehyde and methanol. The James Webb Space Telescope also observed the comet releasing methane, a greenhouse gas that could have helped retain heat on planets in its original system. These findings are significant because the molecules identified are important in studies of prebiotic chemistry—the chemical processes that may lead to life. However, Cordiner notes that while these molecules are essential for building the precursors to life, they do not prove that life has actually developed in 3I/ATLAS’ home system. The organic molecules detected so far have relatively simple structures, and more complex compounds have not been found on the comet despite its long exposure to interstellar radiation. Additionally, most of the chemicals observed were released from the comet’s outer layers, which have been exposed to radiation, rather than from its deeper, more pristine interior. This raises the possibility that these chemicals may not be representative of the comet’s original composition. Despite these uncertainties, scientists continue to analyze the data from 3I/ATLAS, hoping to learn more about the chemical makeup of objects from other star systems. Future observations of interstellar visitors may be made possible by the Vera C. Rubin Observatory in Chile, which is expected to detect similar objects as they pass through our solar system.