Earth at higher risk of big asteroid strike, satellite data suggest

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https://www.science.org/content/article/earth-higher-risk-big-asteroid-strike-satellite-data-suggest

By Paul Voosen, Science. 

Excerpt: At a basic level, humanity’s survival odds come down to one thing: the chances of a giant space rock slamming into the planet and sending us the way of the dinosaurs. One way to calibrate that hazard is to look at the size of Earth’s recent large impact craters. And a provocative new study suggests they are bigger than previously thought—meaning Earth is more at risk of getting hit hard, says James Garvin, chief scientist of NASA’s Goddard Space Flight Center, who presented the work last week at the Lunar and Planetary Science Conference. ...Using a new catalog of high-resolution satellite imagery, Garvin and his colleagues identified large rings around three impact craters and one probable one that are 1 million years old or younger. To Garvin, the rings imply the craters are tens of kilometers wider, and record far more violent events, than researchers had thought. If Garvin is right—no sure bet—each impact resulted in an explosion some 10 times more violent than the largest nuclear bomb in history, enough to blow part of the planet’s atmosphere into space. Although not as destructive as the impact that killed off the dinosaurs, the strikes would have perturbed the global climate and caused local extinctions.... 

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