Via the Professor. Wired has some stunning images of Earth’s old scars – “Asteroid Impact Craters on Earth as Seen from Space”. Including the approximately 290 million years old pair of impact craters that form Clearwater Lakes, Quebec. The larger crater measures 22 miles across. Image: NASA. And A related New Scientist report.
And, also in Canada, here’s a photo of the eroded remains of the 43-mile wide Manicouagan Crater formed approximately 210 million years ago by the impact of an asteroid thought to have been about three miles wide. Image: NASA, STS 9 Crew, 1983.