Scientists Drill for Clues to Dinosaur Extinction

20世纪70年代,墨西哥的Yucatan半岛的石油勘探发现了著名的Chicxulub大坑。直到20世纪90年代,科学家才认定,此大坑是由6千5百万年的一颗小行星撞击地球而形成,这次撞击导致地球上的恐龙灭绝。现在,科学家拟再次对此大坑作一番发掘研究,旨在:to determine once andfor all(一劳永逸的;彻底地)what led to the global extinction(消灭)of the dinosaurs(恐龙)millions of years ago。 本文为读者描绘了当年地球遭受此灭顶之灾时的可怕情景: Millions of years before humans even existed,a huge meteorite(陨星)measuring about 6 miles across and weighing perhaps billions of tons crashed intothe planet in a ball of fire,shrouding the Earth in a dense cloud of dust that blocked out sunlight and sent temperatures plummeting(垂直落下). 文中有一句话颇能引起读者的共鸣: It’s a 100 million-year event—they don’t occur that often,thank God. 文中的一个成语的使用却值得商榷: …hoping to determine once and for all(一劳永逸的;彻底地)what led to theglobal extinction(消灭)of the dinosaurs(恐龙)millions of years ago.在科学探索的道路上,once and for