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66 million years ago, a much larger object hit the Earth, causing a massive extinction.
六百六十万年前，一个更大的物体撞击地球，造成了物种大灭绝。
75 percent of plant and animal species were lost, including, sadly, the dinosaurs.
当时地球上百分之七十五的动植物消失，包括不幸的恐龙。
That object was about 10 kilometers across, and 10 kilometers is roughly the cruising altitude of a 747 jet.
那个物体有十千米宽，而十千米是波音747的巡航高度。
So the next time you're in an airplane, snag a window seat,
所以下次当你坐飞机时，抢一个靠窗的座位，
look out and imagine a rock so enormous that resting on the ground, it just grazes your wingtip.
看着窗外想象一个如此巨大的石块躺在地上，它恰好擦过机翼。
It's so wide that it takes your plane one full minute to fly past it.
它大到飞机需要整整一分钟才能飞过它。
That's the size of the asteroid that hit the Earth.
这是曾经撞击地球的小行星的大小。
It has only been within my lifetime that asteroids have been considered a credible threat to our planet.
这是小行星在我有生以来唯一一次被视作我们星球的威胁。
And since then, there's been a focused effort underway to discover and catalog these objects.
从那以后，人们集中努力发现并分类这些物体。
I am lucky enough to be part of this effort. I'm part of a team of scientists that use NASA's NEOWISE telescope.
我很幸运成为这项工作的一员。我是使用NASA的NEOWISE望远镜科学家小组的成员。
Now, NEOWISE was not designed to find asteroids.
现在，NEOWISE并不是为了寻找小行星而设计的。
It was designed to orbit the earth and look far beyond our solar system
而是环绕地球运动并观测太阳系外的情形，
to seek out the coldest stars and the most luminous galaxies.
寻找最冷的星球以及最亮的星系。
And it did that very well for its designed lifetime of seven months.
而且它在其七个月的预期寿命中非常好的完成了工作。
But today, six years later, it's still going. We've repurposed it to discover and study asteroids.
但是现在，六年过去了，它仍然在工作。我们重新改造让它开始寻找并研究小行星。
And although it's a wonderful little space robot, these days it's kind of like a used car.
虽然它是一个完美的太空机器人，但是现在它更像一辆用过的汽车。
The cryogen that used to refrigerate its sensors is long gone, so we joke that its air-conditioning is broken.
对其传感器进行降温的制冷剂长时间供应不足，所以我们开玩笑说它的制冷系统已经损坏。
It's got 920 million miles on the odometer,
它的里程表上显示已经运行了九亿两千万英里，
but it still runs great and reliably takes a photograph of the sky every 11 seconds.
但它的状态依旧良好并且稳定的在每十一秒拍摄一张天空的照片。
It's taken 23 photos since I began speaking to you.
从我开始和大家讲话到现在，它已经拍了23张照片了。
