Asteroids : Bennu

 As we look farther into the universe thanever before, we may be looking deeper inside ourselves. One of the most surprising facts about ourrelationship with the larger solar system we live in, is that the organics in our bodywere most likely brought here to Earth on comets and asteroids. Rich in molecules called nucleobases, thesame molecules that make up our DNA, asteroids could be the key to unlocking the mysteryof life on Earth. And maybe the very origin of your body, ofthe chemistry that you're using to watch TV right now, came from the asteroids. One asteroid is especially intriguing. Its name? Bennu. In the case of Bennu, it's about half a kilometeracross rock. Bennu itself is an exciting object. It's a carbonaceous asteroid. Carbonaceous means that it contains the elementcarbon, which as we all know are, are associated with life. Bashar Rizk is a scientist at the Universityof Arizona. But it's not just the possibilities of lifethat makes Bennu interesting to Bashar. It's also the possibility of death. Bennu is in a class of asteroids that sharethe same region of space as the Earth as they move around the sun. Every six years, it's in the same generalregion as the Earth, that increases the opportunity that it would actually hit the Earth and causedamage. To understand whether Bennu truly poses arisk to Earth, we need to see it. In the mountains outside Tucson, Arizona,Eric Christensen searches the skies above earth for asteroids and comets. This object that's circled in red here inthe middle, it looks like a faint star, but it just happens to be the asteroid Bennu.

The Catalina sky survey is our first lineof defense against asteroid impacts. Asteroid impacts are really a fact of life. They always happen, they have always happened,they will always continue to happen. We will point our telescope at a particulararea of the sky, and we will build up over time, essentially a very low-resolution movie. We can compare the images and identify starsthat are stationary and then anything that is not stationary is a potential moving object. When astronomers discovered Bennu, they quicklyrealized that of all the near-Earth objects in their sights, this asteroid has one ofthe highest chances of impacting Earth. Bennu had come near the Earth, near enoughthat we could get radar reflection off of it, and therefore we know something aboutits shape. To fully understand where Bennu is going,Peter and Bashar need more than just fuzzy radar images. So, in September 2016, they will launch aspacecraft called OSIRIS REx. After two years of traveling through space,it will intercept the asteroid. Once there, its mission is two-fold. OSIRIS REx will collect a sample of the asteroidto return to Earth, and it will photograph the entire surface in extreme resolution,taking pictures down to the size of a pebble. Our cameras will go and try to characterizethe asteroid's environment. We're gonna image this object to a higherdegree of resolution over a larger piece of its terrain than has ever been done before. Mapping Bennu with these cameras is essential,because we'll understand the gravity of this object to a much more precise degree. Predicting where this object will be 100 yearsinto the future is very important, because this is one of the potentially most hazardousobjects in the solar system, for the Earth. To precisely determine Bennu's future orbit,scientists need to know the asteroid's exact size and shape. That's because of a phenomenon known as theYarkovsky Effect. Any object in the solar system experiencesthe Yarkovsky Effect. Now what is it? Well it's a, it's a thermal asymmetry thathappens because of the rotation of an object.

As the sun's energy strikes Bennu, it graduallychanges the asteroid's orbit. Things have had a chance to heat up. Now when something is hot, it tends to emitphotons, thermal ones. Photons carry momentum. So, what, what this is doing is acting likea little bit of a thrust in this direction. If I thrust that way, I'm kind of increasingthe energy of the orbit, and moving it out from the sun a little bit. The high-resolution images from OSIRIS RExwill tell the team exactly how the Yarkovsky Effect is influencing Bennu's path. If an object the size of Bennu struck theEarth, there would be a regional catastrophe, perhaps taking out as much as a state or severalstates. It could cause a lot of damage and the lossof a lot of life. Space is all about exploration, and it's somethingthat we humans seem to kinda be wired with. History's shown that you've got two choices. You can either keep marching ahead, or youcan fall behind and end up in the dustbin of history. Standing still is not an option. Revealing the deepest secrets from space caninspire wonder. But, they can also incite fear. This grainy image, shows an asteroid calledBennu, and it may be on a collision course with Earth. Odds of Bennu hitting the earth are less thanone in 2,000. That's still considered high for this classof object. Typical odds would hopefully be lower thanone in a million. Bennu is smaller than the asteroid that killedthe dinosaurs, but it could cause a tremendous amount of damage in the, the local area whereit hits. For instance, it could really damage somethingthe size of a, a large city or if it hit just offshore, it could create a tidal wave. In September 2016, Bashar and Peter will senda probe to photograph Bennu in detail and reveal its secrets. But a mission like this is fraught with potentialpitfalls. In August 2014, a spacecraft called Rosettaarrived at another small body, a comet, caught in Jupiter's gravity. Three months later, the Rosetta team attemptedto land a probe called Philae on the comet's surface, and it ended in disaster. Philae was equipped with a couple of harpoonsso that when it made its landing, they would shoot out and ideally try to moor it there. Except that, apparently, the harpoons didnot fire when Philae landed. So, because of that, Philae hit the surfaceand bounced, and it bounced several times because of the comet's rotation and, and thelander zone velocity. And it wound up coming down in an area ofthe comet that we didn't have good maps for, and so basically, the lander was lost. The team is determined to see their missionsucceed, that's because there is more to learn from Bennu than whether or not it will collidewith Earth. It could unlock the origins of life on ourplanet.

The Earth formed when objects slammed together. But later on, as it cooled, and water becamea large part of the surface composition, then it was possible for future impacts with smallerobjects to actually bring in organic materials that could survive on the surface. And that's how many people think organicscame to the Earth, is through those impacts from asteroids. When we get a sample of Bennu back into ourlaboratories, we're gonna be looking at material that formed in the initial phases of the formationof the solar system. If we could someday prove that the buildingblocks of life on Earth actually came from space and, and not from our own planet, itwould turn everything we understood about the origin of life on its head. OSIRIS REx will not attempt a landing likePhilae. Instead, it will get a sample of the asteroidwith a revolutionary new system called TAGSAM. TAG stands for Touch and Go and SAM is SampleAcquisition Maneuver. So TAGSAM is the actual act of reaching out,touching the surface of the asteroid, and gathering then sample, then pulling away. Once samples from Bennu arrive back on earth,we can test them for the kinds of organic materials that could have seeded Earth fourbillion years ago. But to successfully retrieve the sample, thecameras must function perfectly. The cameras are one of the critical experimentson this mission because as we get closer, it can refocus and actually becomes more likea microscope, and it can detect grains that are just a few millimeters across. So, when we get to our sample site, we wannaget the highest resolution possible. The OSIRIS REx camera suite consists of threecameras, a low resolution, medium resolution and high-resolution cameras, with overlappingfunctions that are meant to carry out, or fulfill the requirements for imaging for themission. We're trying to get deeper and deeper intohow the, the cameras work. The reason we're doing this test is to findout how the camera responds to different colors. 'Cause when we get to the asteroid, we wantto know when we take color pictures, what the true color of the asteroid is. Different minerals have different signaturesin this, in this manner.

Like, for example, rust is orange. Olivine crystal which you can find in sand,and volcanic glass, can be orange or yellow or green, and so just by looking at the colorof an object you can actually sort of tell what it is, very roughly. And the, the more finely you can parse outthose colors, the more narrow the, the color you can look at, the better you can tell whatan object is. So, by mapping colors of light, they'll beable to say "Where is the best place to send our probe so that we can the most scientificallyinteresting material that we possibly can to bring back to Earth?" Alright, can you hit the lights? Right, what we're about to do here is we'reabout to try to scan where we're gonna change the, the color of the light that's being sentinto this sphere that the camera is lookin at. And then the camera's gonna be taking picturesof the light, different colors, as the light is being scanned to characterize how sensitiveit is to those different wave lengths. In the last month and a half, we've had about15 different major tests, and I think that having been successfully completed, producesa big sigh of relief in everybody involved. The things that keep me up on a night arebig things. Things that we miss during the calibration. You don't know what you don't know. We are in an ever-present position of tryingto get rid of our, our fears and uncertainties about what might happen.

With only months to go until lift off, theclock is ticking to get OSIRIS REx right. We'll be launching in September of 2016. So, we have a schedule pressure here thatI think does take its toll on the team. There are a number of things that we're tryingout for the first time. And that keeps people up at night at NASA. Should the mission fail, NASA will need anotherway to reach Bennu. Scientist Ben Hockman created a backup planand to test it, he's hitting the beach. I think most people assume asteroids are justbig rocks in space. When in fact they have very interesting surfacegeology. We've found through recent missions that therecan be a wide variety of different surface features. With its mix of sand and rocks, this beachmimics terrain that NASA has observed on comets and asteroids. It is the perfect place to test Ben's rover,nicknamed Hedgehog. Hedgehog's a whole new class of rovers. Very different from the previous rovers thatwe've sent to the Moon and Mars. We have seen that the topology of asteroidscan be very uneven, so there's potential that a rover could fall into a pit, or a crater,and be unable to escape. Alright, hopefully this works. It may not look like much, but on an asteroid,where gravity is a tiny fraction of the Earth's, this same hop would propel Hedgehog far acrossthe surface. It uses three internal fly wheels to buildup momentum internally, and by doing that, it can hop and tumble across the surface. These spinning fly wheels build up momentum,and when Ben applies the brakes, he transfers that momentum into motion. Think about it like you're driving your bikeand you come to an obstacle, and you hit your front brakes. You have a lot of momentum about your frontwheels so you have a tendency to want to flip over your front wheel. The same is true for Hedgehog, but we do thatto our advantage, to hop in a controlled way. But to see how Hedgehog will work in a nearzero-G environment, Ben must head to the lab at Stanford University. So, this contraption is called our micro gravitytest bed. The micro gravity test bed allows us to emulatewhat the rover might do in actual micro gravity conditions. The bed shows Ben how Hedgehog will behaveon an asteroid like Bennu. At those scales, gravity is about 1,000 or10,000 times lower than that of Earth. So, on an asteroid, a human would weigh asmuch as a paper clip. One of the key advantages of Hedgehog is thatthere's no right way up. In other words, it can land on any side, andbe just as capable of moving as if it were to land on its feet so to say. And Hedgehog holds one other advantage. Because Hedgehog is so compact, and cheap,you can store potentially many of them in a spacecraft that you send to a small body,so you could imagine an army of Hedgehogs hopping around the surface, exploring thephysical properties of an asteroid. For now, Hedgehog is only a prototype, soit will be up to OSIRIS REx to unlock the secrets of Bennu. The answers won't come until late 2018, whenOSIRIS REx and its cameras finally reach the asteroid. I think the, the images of Bennu are goingto be revelatory. Waiting for those images to come back in 2018and 2019 will be... the only thing I could compare it to would be the, waiting for thebirths of my two children. Because something very important to you, andyou're not quite sure of the outcome. Until then, scientists can only wonder ifBennu will change our understanding of life on Earth. How did all that get going? Did it start here? Or was it brought here by, from outside? We don't really know the answer to that. We're gonna go find out.