地外撞击理论80年代初期,美国著名物理学家路易斯·阿弗雷兹和他的儿子瓦尔特·阿费雷兹在距今6500万年的白垩纪/第三纪(K/T)界线粘土层中发现了比背景值高出几十倍的铂族元素(PGE)铱(Lr)的异常变化,最高达9.1ppb,由于在地球漫长的演化过程中,铂族元素主要集中于地核和地幔中,而在地壳中极度亏损,相对太阳系亏损系数可达几万到几十万倍,因此认为,K/T界线如此高的铱异常不大可能由地内作用产生,而可能与地外物质有关。经过进一步研究形成了地外撞击理论。这一理论认为,在白垩纪末期(距今6500万年前后),有一颗直径约10公里的小行星突然撞击地球,其巨大的动能使得地球物质融化甚至气化,并将大量物质抛向空中,造成大量尘埃物质悬浮于平流层,遮天蔽日,长达数年之久。从而使透光率降低,光合作用受阻,食物链中断,导致了包括恐龙在内的地球生物的大规 Extraterritorial impact theory In the early 1980s, the famous American physicist Luis Alfredz and his son Walter Afeliz in the 65 million years of Cretaceous / Tertiary (K / T) boundary clay (PGE) anomalous change of up to 9.1ppb, due to the long evolution of the Earth, the platinum group elements are mainly concentrated in the core and Therefore, it is considered that the high Iridium anomaly at the K / T boundary is not likely to be caused by the in-site interaction with the extra-terrestrial material related. After further research has formed the extraterrestrial impact theory. According to this theory, at the end of the Cretaceous (about 65 million years ago), a small asteroid with a diameter of about 10 km hit the Earth suddenly. Its huge kinetic energy makes the Earth’s materials melt and even vaporize, and throws a large amount of material into the air , Resulting in a large amount of dust suspended in the stratosphere, covering the sun, for several years. Thus reducing the light transmittance, obstruction of photosynthesis, food chain disruptions, led to the Earth, including dinosaurs, including the large scale