Astronomers detected five ion species simultaneously in the plasma tail of interstellar comet 3I/ATLAS, including ionized molecular nitrogen, using the WEAVE instrument on the William Herschel Telescope. The unusually strong nitrogen signature relative to carbon monoxide points to formation at temperatures of roughly 30 kelvins or below, suggesting the comet assembled in the frigid outer reaches of another planetary system. Measurements along the tail also showed that most ion ratios remained stable over the observed distances, while CH+ appeared to decrease slightly, offering an unusually detailed look at plasma chemistry in an interstellar comet. The third known object to enter our solar system from interstellar space appears to have been born in an environment far colder than the region where many familiar comets formed. Astronomers studying 3I/ATLAS detected an unusually strong signature of molecular nitrogen in its plasma tail, alongside four other ionized species. The chemical mixture points toward formation in temperatures around 30 kelvins or lower, roughly minus 243 degrees Celsius. “This object gives us a rare chance to study material that formed somewhere …