Today, I want you to join me on a journey. It's a journey to answer some of the deepest questions that we ask ourselves as the human species. Where did we come from and how did the Earth come to be a habitable world? When we go back to the dawn（黎明） of the solar（太阳的） system and we reconstruct（重建） the events early in the stages of the formation of Earth, we recognize that it was a hot, hellish, hazardous（危险的） environment, constantly（不断地） bombarded（轰炸） by fragments from outer space. One of those fragments（碎片） was so large, it spalled off a chunk（大块） of material that accreted（共生） into our moon. And when we look at the geologic（地质的） record from that era（时代）, we realize there's no way that life as we know it would have taken hold（拿住） in such an environment.

  And so we ask ourselves, where did the Earth get the key components（成分） for life? When we look at the Earth today, we think of it as this beautiful blue jewel in the solar system covered in oceans, clouds and rains and rivers running across the continents. Perfect abode for the myriad（无数） of life forms we share this planet with. And we wonder, where did that water come from that makes（使） up our oceans? Where were the molecules that make up the air that we breathe? And most importantly, where did the carbon（碳） come from that is the central element to all life on Earth?

  And when we look out into the solar system, out beyond（在…的那边） Mars, we see a belt of asteroids（[天] 小行星）, remnants（残余） from the earliest stages of planetary（行星的） formation（形成）, relics（遗物） that are over four and a half billion years old. Some of them stand out to us, their surfaces are very dark, which we intuit means they may have carbon. Carbon does make things very black. Some of them, we look at the way they absorb（吸收） sunlight and we see that there are minerals（矿物） on the surface, clays with water locked up in their crystal（结晶） structures. And we wonder, could these have been the key that delivered these essential components to the Earth? For the past 20 years, I've been on a personal journey and a professional expedition to answer those questions.

  On September 8, 2016, we launched（发射） a robotic spacecraft（航天器） named Osiris-Rex to a near-Earth asteroid（[天] 小行星） named Bennu. And Bennu called to us to answer these questions. Its surface was one of the darkest in the solar system. Its orbit brings it very close to our homeworld, so close that we actually worry that it might strike（打） the Earth in 160 years. But we're not talking about that today. Today, we're interested in Bennu as this repository of the history of our solar system and holding the clues to the origin（起源） of life on Earth.

  We arrived at this target in 2018, and right away, when you see the shape of this asteroid, it's not that big. It's about 500 meters, about the size of the Empire（帝国） State Building. And it has this almost spherical（球形的）, what we call spinning（纺） top shape, suggesting that it's behaving somewhat（有点） like a fluid（流体）. And as we'll see, that's not too far from the truth. But the first thing that leaped（跳） out to me when those resolved（解决） images came down to the Science Operations Center here on the campus of the University of Arizona was how rough and rugged the surface was. When we analyze our telescopic（望远镜的） data, radar（[雷达] 雷达） data from the Arecibo Telescope in Puerto Rico, infrared（红外线的） information from the Spitzer Space Telescope, it looked smooth, like a beach.

  I even said to NASA, to the public, to my team, we're going on vacation to Bennu Beach.