美国有线新闻 CNN 北极地区出现神秘陨石坑（在线收听）

Where would you find the largest known impact crater on Earth? South Africa, Siberia, Antarctica, or Mexico. South Africa's Vredefort crater is the world's largest known impact crater.

以下哪个地方可以找到地球上已知最大的陨石坑？南非、西伯利亚、南极洲还是墨西哥？南非的弗里德堡陨石坑是世界上已知最大的陨石坑。

An impact crater, as the name suggests, is formed when something like an asteroid crashes into something else like Earth. This more recent phenomenon was not caused by an impact but it is one of 17 craters that have mysteriously appeared in the Russian arctic since 2013.

陨石坑，顾名思义，是小行星撞击地球等天体时形成的。但最新出现的陨石坑并非由撞击形成，而是2013年以来神秘出现在俄罗斯北极地区的17个陨石坑之一。

Scientists don't know for sure how this happened. They do know the hole's about 150 deep. Picture three city buses measured end to end and after it was discovered last summer, they flew a drone inside the crater to capture dozens of images from which they built a three-dimensional model. That helped researchers to hypothesis this.

科学家尚不清楚这是如何形成的。他们知道这个洞有150英尺深。这个坑的直径是三辆城市巴士首尾相连的长度，在去年夏天被发现后，人们驾驶一架无人机在陨石坑内拍摄了数十张照片，并根据这些照片建立了一个三维模型。这有助于研究人员进行假设。

Methane gas somehow accumulates in the permafrost of Siberia. They're not sure whether the gas comes from deep inside the Earth or near its surface but they believe that as the methane builds in a cavity in the ice it forms a mound. And that mound grows until if finally explodes, blasting ice and other debris and leaving behind the crater.

甲烷气体以某种方式在西伯利亚的永久冻土中积聚。他们不确定这些气体是来自地球深处还是地表附近，但他们相信，甲烷在冰的洞穴中堆积时，就会形成土堆。这个土堆会不断扩大，直到最终爆炸，喷出冰和其他碎片，留下陨石坑。

Scientists are using computer technology to try to predict where this will happen next. These craters appear in sparsely populated areas. They're usually discovered on accident by reindeer herders or during helicopter flights of the area.

科学家正在使用计算机技术，试图预测这种情况接下来会发生在哪里。这些陨石坑出现在人口稀少的地区。它们通常由驯鹿牧民偶然发现，或是直升机飞经该地区时意外发现。