For millions of years, a fragment of ice and dust has drifted between the stars — a frozen message in a bottle from another world. This summer, that message reached our solar system as 3I/ATLAS, only the third known interstellar comet. Using NASA’s Neil Gehrels Swift Observatory, Auburn University scientists detected the comet’s faint ultraviolet signature of hydroxyl (OH) — a by-product of water vapor — revealing that this visitor from another star is actively releasing water into space. Swift’s unique vantage point above Earth’s atmosphere allowed the team to capture ultraviolet light invisible to ground-based telescopes, uncovering new clues about how icy bodies — and the ingredients for life — form in planetary systems beyond our own.