Though not visible to the naked eye or even with binoculars, the green-tailed Comet 45P/Honda-Mrkos-Pajdusakova (HMP) did not escape the gaze of the world-renowned Arecibo Observatory. Scientists from the University of Arizona’s Lunar and Planetary Laboratory (LPL) and the Universities Space Research Association (USRA) at Arecibo Observatory have been studying the comet with radar to better understand its solid nucleus and the dusty coma that surrounds it.