Back in October 2012, a small (45-100 feet, or 15-30 m) asteroid known as 2012 TC4 had a close encounter with Earth. It passed our planet at a distance only a quarter of that between the Earth and the Moon. On October 12, 2017, this asteroid will make another close flyby of Earth. This encounter will be used by asteroid trackers around the world to test their ability to operate as a coordinated International Asteroid Warning Network. 2012 TC4 appears...
