[ti:Study: Huge Meteorite Crater in Greenland Much Older than Suspected] [by:www.51voa.com] [00:00.00]更多听力请访问51VOA.COM [00:00.04]Scientists say a huge crater formed [00:05.04]by a meteorite strike in present-day Greenland [00:09.84]is much older than first thought. [00:13.12]The 31-kilometer-wide crater was first discovered in 2015 [00:21.60]under thick ice at Greenland’s Hiawatha Glacier. [00:26.72]The ice covering the crater, called an ice sheet, [00:32.48]is about one kilometer deep. [00:35.72]The crater remained hidden until it was identified [00:40.68]by radar equipment and scientists decided to investigate. [00:46.36]At first, researchers estimated the massive hole [00:52.04]might have formed about 2.6 million years ago, [00:56.96]or even as recently as 13,000 years ago. [01:03.20]But they announced March 9 that new dating methods [01:08.60]suggested the crater is about 58 million years old. [01:15.00]The researchers said they based their findings on dating methods [01:21.68]that measured the breakdown of radioactive material. [01:26.80]Their results were recently released in a study [01:31.40]in the publication Science Advances. [01:35.16]The new information suggests the strike [01:39.92]happened about 8 million years after an asteroid [01:45.52]hit an area in Mexico’s Yucatán Peninsula. [01:50.84]That climate-changing event is blamed for causing the disappearance [01:57.28]of more than 70 percent of Earth’s plant and animal life. [02:03.00]All dinosaurs that were not bird-like disappeared. [02:08.24]At the time the meteorite hit Greenland, [02:12.72]it was not the icy place it is today. [02:17.12]It is believed to have been covered with rain forests [02:22.20]populated with plant and animal life [02:26.04]that followed the disappearance of most of the dinosaurs. [02:31.20]Researchers say the meteorite released millions of times [02:37.32]more energy than an atomic bomb, [02:41.04]leaving a crater big enough to swallow the city of Washington D.C. [02:48.16]Gavin Kenny is with Sweden’s Museum of Natural History [02:54.24]and was the lead writer of the study. [02:57.48]He told Reuters that forceful air from the event [03:02.76]"would have knocked down most trees within tens to hundreds of kilometers.” [03:09.44]In addition, an explosion from the strike [03:13.52]would have set trees on fire and caused widespread forest fires. [03:20.24]Michael Storey, with Denmark’s Natural History Museum, [03:26.16]was a co-writer of the study. [03:29.00]He said the new information does not provide clear evidence [03:35.32]that the impact had long-lasting effects on world climate. [03:40.92]But, Storey added, he thinks such effects were “unlikely.” [03:47.92]Kenny noted that these kinds of strikes [03:52.04]only happen every few million years. [03:56.28]So, he said, “We don't need to be very worried [04:00.84]about such an impact happening anytime soon." [04:05.72]I’m Bryan Lynn. [04:08.00]更多听力请访问51VOA.COM