The closing of the Isthmus of Panama, cutting off the equatorial flow between the Atlantic and Pacific oceans, was just about complete 5 million years ago when, in the far reaches of the solar system, 50,000 times farther from the sun than Earth, two hill-sized hulks of rock, dust and volatile ices had a close encounter. The gravitational tug sent one of them plunging toward the distant sun appearing slightly dimmer than Venus does to us. It has taken all these years for that hulk, now Comet Pan-STARRS, to plunge to the inner solar system. It was just inside the orbit of Saturn and very faint on June 6, 2011, when it was discovered by the Panoramic Survey Telescope and Rapid Response (Pan-STARRS) facility in Hawaii. In March of 2012, J.J. Gonzalez of Leon, Spain, was the first amateur astronomer to spot it. It became visible with binoculars in January of this year and had formed a tail by February that southern hemisphere observers have imaged.