A selection of evidence, including a carbon isotopic excursion, iridium anomaly, fullerenes (C 60 and C 70 ) with trapped noble gases, microspherules and shocked quartz, is discussed in this paper. All the evidence in hand favors the hypothesis that the PTB event was probably related to an extraterrestrial cause, and the impact would lead to great physical change, including large volcanic eruptions on the earth’s surface. The ET markers for the CTB event could be considered only as an example, and cannot be taken as a unique standard of an ET event. A selection of evidence, including a carbon isotopic excursion, iridium anomaly, fullerenes (C 60 and C 70) with trapped noble gases, microspherules and shocked quartz, is discussed in this paper. All the evidence in hand favors the hypothesis that the PTB event was probably related to an extraterrestrial cause, and the impact would lead to great physical change, including large volcanic eruptions on the earth’s surface. The ET markers for the CTB event could be considered only as an example, and can not be taken as a unique standard of an ET event.