小行星撞地球或使人类变成"吸血鬼"

　　An asteroid splashdown in one of Earth's oceans could trigger a destructive chemical cycle that would wipe out half of the ozone layer, according to a new study. The massive loss of protection against the sun's ultraviolet (UV) radiation would likely force humans into a vampire-style existence of staying indoors during daylight hours.

　　最新科学研究显示，小行星坠入地球海洋会引发毁灭性的化学连锁反应，导致50%的臭氧层消失。缺少了臭氧层对太阳紫外线辐射的抵挡，人类将有可能被迫过起“吸血鬼”般的生活——白天只能躲在屋子里。

　　The worst scenario based on an asteroid 1 kilometer wide would re-create the hole in the ozone layer, which appeared over Antarctica during the 1990s, except this would be worldwide. UV levels in the study's simulation soared beyond anything measured so far on Earth by the UV Index's daily forecasts of overexposure to UV radiation, and remained that way for as long as two years.

　　早在上世纪90年代，南极洲上空就已出现臭氧空洞。此次研究发现，直径达1000米的小行星撞击地球后也会出现臭氧空洞，且危害波及整个地球。研究结果显示，模拟太阳紫外线辐射在撞击后飙升，超过了此前在地球上测量的所有紫外线辐射指数预报数据，并且会以这种状态保持两年。

　　Researchers tested scenarios with a 0.6-mile asteroid and a 0.3-mile asteroid (500 meters) at a specific location and specific time of year. Models used in the research showed how ozone destruction would result from an asteroid strike launching seawater vapor hundreds of miles up into the highest parts of the atmosphere. Chemical elements such as chloride and bromide that separated from the water vapor could then wreak havoc by destroying the ozone layer that protects life on Earth from UV rays.

　　在实验中，研究人员测试了特定时间特定地点下直径分别为1000米和500米的小行星。研究人员通过观察模型发现了小行星坠落入地球海洋后的臭氧层破灭过程：巨大的撞击力量使得海水蒸汽上升至大气层最高点，随后氯化物及溴化物等化学物质脱离水汽，毁坏保护人类免受辐射的臭氧层。

　　Long-term effects of such high UV radiation would include skin-reddening, changes in plant growth and genetic mutations for humans and other organisms. And an asteroid has about twice the chance of striking water rather than hitting land. Those odds come from the fact that over 70 percent of the Earth's surface is covered by water.

　　据悉，长期面临辐射可导致皮肤红化、植物生长发生改变、人类以及其他有机体的基因变异。而且据了解，小行星落入海洋的几率是与陆地相撞几率的两倍，原因在于地球70%以上的表面被水覆盖。