阿克拉曼火山口, 澳大利亚 The Acraman crater, Australia (© USGS/NASA Landsat data/Orbital Horizon/Gallo Images/Getty images)

阿克拉曼火山口, 澳大利亚 The Acraman crater, Australia (© USGS/NASA Landsat data/Orbital Horizon/Gallo Images/Getty images)

Will we be ready for the 'big one'? 我们准备好迎接“大挑战”了吗？

Asteroid Day

Today is Asteroid Day, and it's a reminder that as our planet follows its path around the sun, it encounters a lot of stuff. Science tells us that, every day, Earth's atmosphere is hit with roughly 100 tons of dust and particles the size of a grain of sand. And every year, at least 30 small meteors make it through, only to burn up before touching the ground. NASA says it's pretty much guaranteed that at least one of them will be about the size of a car. As time progresses, the likelihood increases that even larger celestial rocks will hit the ground and cause significant damage.

Across the globe, there are plenty of reminders of this in the form of craters, like the one in today's photo. The Acraman crater is a point of impact in South Australia. It's believed to have been created about 590 million years ago when hit by an asteroid with a diameter that could have been as large as 56 miles across. For comparison, the asteroid thought to have killed the dinosaurs 66 million years ago was 6.2 miles across. NASA says that an asteroid the size of a football field would cause significant damage. One that could really threaten civilization hits every few million years. Hopefully, with Asteroid Day being observed across 78 countries since its inception in 2015, we'll be prepared when the 'big one' shows up.

小行星日

今天是小行星日，它提醒我们，当我们的行星沿着它围绕太阳的轨道运行时，它会遇到很多东西。科学告诉我们，每天，地球大气层都会受到大约100吨沙粒大小的灰尘和颗粒的撞击。每年，至少有30颗小流星穿过，但在到达地面之前就被烧毁了。美国宇航局表示，几乎可以保证其中至少有一辆车的大小。随着时间的推移，更大的天体岩石撞击地面并造成重大损害的可能性增加。

在全球范围内，有很多火山口的形式提醒着我们这一点，就像今天照片中的一样。阿克拉曼火山口是南澳大利亚的一个撞击点。据信，它是在大约5.9亿年前被一颗直径可达56英里的小行星撞击时形成的。相比之下，被认为在6600万年前杀死恐龙的小行星直径为6.2英里。美国宇航局表示，足球场大小的小行星将造成重大破坏。每几百万年就会有一次真正威胁文明的袭击。有希望的是，自2015年小行星日成立以来，全球78个国家都在纪念小行星日，我们将在“大一号”出现时做好准备。