It’s a quest spanning the inner solar system, all spurred by scientists’ enthusiasm for the rare detection of an interstellar object. “Each one of these has been special and precious, and everybody drops everything to look at them,” says Karen Meech, a planetary astronomer at the University of Hawaii. And in an era when scientists are not yet able to launch a specialized mission to catch these strange visitors, recruiting spacecraft that are already exploring the solar system to do the job is the next best thing. “You’ve got kind of a mission for free,” Meech says.