Comet 3I/Atlas continues to be full of surprises. As well as being only the third interstellar object ever detected, new analysis shows it is producing hydroxyl (OH) emissions, with these compounds betraying the presence of water on its surface. “When we detect water—or even its faint ultraviolet echo, OH—from an interstellar comet, we’re reading a note from another planetary system,” said Dennis Bodewits, an Auburn University physicist who collaborated on the research, in a press statement. “Every interstellar comet so far has been a surprise,” said Zexi Xing, an Auburn University researcher and coauthor of the discovery, in a press statement. “‘Oumuamua was dry, Borisov was rich in carbon monoxide, and now ATLAS is giving up water at a distance where we didn’t expect it.