Scientists begin to study Bennu asteroid samples

Fragments from the asteroid that has been described as “the most dangerous rock in the Solar System” have arrived in the UK for study. The tiny pieces of rock and dust from the object known as Bennu will be subjected to testing by researchers at the Natural History Museum, and the Open, Manchester and Oxford universities. Chris Smith spoke to Sara Russell, a professor of planetary sciences and leader of the Planetary Materials Group at the Natural History Museum.

Sara - What we actually have in London is two glass slides stuck to each other, which have got a little kind of depression in them. And inside this little depression is a teaspoonful of a black powder. It sort of looks like sugar. If sugar was black, this is what it would look like. And yeah, it's just the most exciting thing that I've seen because we've been waiting for this for a long time. <Laugh>,

Chris - How did it get to you?

Sara - So this is an asteroid from NASA's Osiris-Rex mission, which has been a long time in the planning, but it actually launched in 2016 from Cape Canaveral. So I was there with my family. We watched this rocket blast off into space; didn't see it for seven years until September this year, when the spacecraft returned from the asteroid, it had been visiting which asteroid, Bennu, a near-Earth asteroid. So it had collected a piece of the surface of the asteroid and then made its way eventually back to Earth. And the spacecraft dropped the container at the top of the atmosphere where it landed in Utah. The spacecraft has now gone off to explore some other asteroids.

Chris - It's dubbed the most dangerous asteroid in the solar system at the moment. Isn't it Bennu? Why has it got such a bad rep?

Sara - <Laugh>. Yeah; well, so Bennu is what's called a near-Earth asteroid, which means it orbits the sun in a similar path to that of the Earth. And every so often it gets really close to Earth and there's a chance that in 200 years or so it might even impact the Earth. But the odds of that happening are actually really, really small. But the probability of that happening, as well as its size mean that, yeah, it has been dubbed the most dangerous object in the solar system. So one of the aims of the mission was to learn more about its precise orbit so we can work out exactly what its path would be in the future and also bring this material back to earth so we can learn more about the properties of the material. So if we ever do need to deflect it away from earth, we know what we're dealing with

Chris - And what are we dealing with. What can you tell from your initial looking at this?

Sara - It's exceeded our wildest dreams. So one of the things we've discovered so far is that it contains loads of carbon. It contains several per cent carbon, which is mostly in the form of organic material. And that's really exciting 'cause it's possible that asteroids like Bennu have pelted the early Earth and brought down all the nutrients that were needed for life to flourish. And we also know so far that it also contains loads of water. So the most abundant mineral in it is a kind of clay mineral that can suck up water inside its structure. We're really interested in finding out, you know, where all this water came from. And that will tell us something about how water moves around the solar system. It may eventually tell us how we got to be on this habitable watery planet.

Chris - How do you actually work with it and how do you make sure that you don't accidentally introduce Earth to it?

Sara - Yeah, so that's one of the big challenges of dealing with this sample. So we do have other bits of asteroid on earth in the form of meteorites, but they've all been in contact with the Earth's atmosphere. So, to various degrees, they're slightly contaminated. So this one of the things that makes this sample return material really, really special. And so, so far it has not been in contact with the Earth's atmosphere at all. So we keep it in a nitrogen box and we handle it by putting our hands into these big thick rubber gloves which go into the box and then we can manipulate it that way.

Chris - And what sorts of tests are you doing? I, I know you're, you're giving some details about the composition and things, but many laboratories could do that. So what special extra pizazz is <laugh> your skill at the Natural History Museum going to bring to this party?

Sara - Yeah, so we really specialise in mineralogy. So we're going to really kind of dig into what minerals this asteroid is made of. So we've got some special techniques. So for example, we've got one technique called X-ray diffraction that fires a beam of X-rays at the sample. And then the interaction of the minerals with the X-rays deflects them in different directions. And by measuring that, we can find out exactly which crystals we are dealing with. So we're going to do that. We're going to do CT scanning. So that's the same sort of piece of equipment that you have in hospitals to look inside humans. We can also use that to look inside the sample and see what its structure is like. And we'll also use electron microscopes to look in really fine detail what it looks like and also find out what its chemical composition is that way.

Chris - And I know you're saying that by CT scanning it, you get some clues as to the structure. Does that tell you anything about the structure of the thing it came from? Because that at the end of the day is one of the things you said was a goal here to try and understand more about the parent body and the risk it might pose. But does that tell us anything more about Yeah. What it was doing out there in the solar system right back early in history?

Sara - Absolutely. Yeah, that's exactly the aim of this work. So, one of the great things about this mission is that we've got this sort of big scale information from the spacecraft going to the asteroid and taking pictures and taking measurements of the whole asteroid and looking at its surface in detail. We also have the opportunity to look at this really fine scale information about what these little bits of dust look like and we can try and link the two to each other. One of the things we found when we looked at the surface of the asteroid was that it, there are actually several different kinds of rocks on the surface, which suggests it's actually a kind of rubble pile made up of different boulders, some of which might have come from other asteroids! So it might be that we can actually sample loads of different asteroids by looking at our little grains one by one.

Chris - How long is this gonna take you, Sara?

Sara - <Laugh>? The rest of my career, Chris <laugh>. But so each grain can take us weeks to properly characterise. So it's gonna be a long haul. We'll get the first results out next year. And the mission officially, this kind of analysis stage of the mission lasts for two years. So it lasts until 2025. So, we'll be going all guns ahead until then for sure.

Chris - Are you tempted on April the first to ring up NASA and say, "I've got a bit of bad news... I've dropped it!"

Sara - <Laugh>. I am now <laugh>. No, that would just be too awful. That's honestly my worst nightmare. Every time I touch it I sort of fear I'm gonna have some spasm or something and our whole sample will be lost. So that's is just too close to the bone to even joke about!