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How Rosetta can help decipher a comet’s secrets

After a 10-year journey, the space probe Rosetta is orbiting a comet. The spacecraft is slated to follow the comet for more than a year on its way toward the sun. Hari Sreenivasan talks to Mark McCaughrean, senior scientific advisor of the European Space Agency, about sifting through a cosmic “garbage pile” in hopes of learning about the building blocks of life.

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    It's taken 10 years and a journey of 4 billion miles, but, today, a spacecraft began orbiting a comet, a first in space history, and a mission that may tell us something about the origins of life itself.

    Hari Sreenivasan has our conversation, which was recorded as part of a Google Hangout earlier today.


    After a billion miles and 10 years in space, the Rosetta spacecraft, launched by the European Space Agency, it's finally near where it's supposed to be.

    That's flying right now to a comet at 35,000 miles per hour. It took an amazing feat of rocket science and precise maneuvering to get the satellite close. And it will take even more to perform the next part of the mission by November. That is to get close enough to send a probe that will land on the comet.

    The first images were sent back today.

    Mark McCaughrean is the senior science advisory with the European Space Agency. He joins me now.

    So, why do we want to send a satellite this close to a comet?

  • MARK MCCAUGHREAN, Senior Scientific Advisor, European Space Agency:

    That's a great question.

    There's many things we could do, but comets are the repository of information about the origin of our solar system. They're leftover bits and pieces, if you like, the garbage pile that is left over from when the planets were made. That material is pristine, primordial, pretty much untouched.

    And by rummaging through that garbage pile, if you like, we can start to learn about how our solar system is built, but not only that, because these comets have got a lot of water in them. And they perhaps hold the answer to a long — a mysterious question that has baffled people for a long time.

    If the Earth was really hot when it was first made, which it was, how did water stay on the planet? It would have boiled off? Maybe it came later or maybe it came from something like comets. So, the cup of coffee you had this morning, maybe you're actually drinking stuff that came from a comet.

    And on top on that, we know that comets are really dark. They're not snowballs. They're very, very black. And they have got stuff in them which is dust, but also organic, complex molecules, including amino acids, the buildings blocks of life. So comets could have also seeded the Earth with the raw materials for making who we are today. So there's — if you like, there's the loop.


    Now, we have gotten close to comets before, so why do we need to orbit one?


    All the other mission have been quick flybys, because it's actually easier — much easier — or, in terms of spaceflight, rocket science — to fly past a comet very quickly instead of work our way around the solar system using the other planets, using Earth and Mars to kind of bend our trajectory around to get to — actually slow down and get to the right speed to rendezvous.

    So we have learned things about comets, but just for a few minutes at a time. This time, we are going to watch this comet as it comes into the inner solar system, heats up, evolves, changes, gets dynamic. There is going to be so many unexpected surprises, but we will be able to then use that to link what we see from the comet close up to what we see from comets from distances, and use it as a — exactly what the name suggests, a Rosetta stone for understanding comets in general from being close up to this one.


    Let's talk a little bit about what this took to accomplish. We're talking a 10-year-long project, scientists and equipment from all over.


    In some ways, it's actually a lot longer than that, because, in 1986, the European Space Agency did a first. It was the first ever flyby of a comet, Comet Halley, on its famous passage back in 1986.

    And then there was the genesis of the idea to actually start, saying, flying by at 68 kilometers a second and seeing a few minutes' worth of data is good. But what would it be like to go there and stay there for a full year and maybe even land?

    So, that was then. By 1993, the mission had been approved. It took 10 years to build it. And then we had to launch it. We had a year's delay, not on our side, in the sense the mission was ready, but one of our rockets exploded and we had to then revisit that and try to work out what was wrong with that.

    And we lost the first comet we were supposed to be going to. It had moved on. We had to pick another one quickly. And now we have been in space for 10 years. And what I have been saying is, being in the cars for 10 years, the kids in the back being — getting a bit irritated. Are we there yet?

    And we're there now. We haven't got out of the car. We're looking out the window. And there's scientific Disneyland just waiting for us. It's the most astonishing project — comet to get to — sorry — right at the end. What an amazing place to land on. We couldn't have wished for better.


    You're going to try to land on the comet. I have even heard the word harpoon.


    Yes, literally, yes.

    You might think we would take a bit of time off now, having had a good rendezvous today, and have a glass of champagne, but we can't relax, because we're at the perfect time. We're at a Goldilocks time now. The comet is moving in from its orbit.

    Its most distant point from the sun is beyond the orbit of Jupiter. It's cold out there. There's not much sunlight. We couldn't power the spacecraft fully out there. But coming in, we have got enough power to power the spacecraft now. And the comet is not too active yet.

    But comet will be getting active soon. And we want to land before it gets too active to kind of lower the risk. And that means we have to land by November. We have three months now to pick a landing site, both technically, scientifically, risk-wise, and get the thing down on the surface, so it is going to be a frantic period, really exciting as well, though.


    So, what happens to that object after it lands? I have heard that they're both hurtling toward the sun.


    It's a little — I know. We all have these pictures of things going so close to the sun they break up and don't come back out again. Comet ISON last year was one such object.

    Kind of the dirty secret here is this comet never comes as close to the sun as the Earth even. It ends up — its closest to the sun is 184 million kilometers out, so somewhere between the Earth and Mars.

    It will have a tail. It will develop a big coma, the gas and dust blowing away. So, we will learn a lot. But it's never in danger of being so bad that we risk the mission.

    One of the interesting little side facts is, people will want to know where they can go and look and see the comet. Don't bother. You won't be able to see it naked eye. You will need a pretty big telescope to see it at all. But you don't have to worry. We have a ringside seat. We will show you it from close up.


    Mark McCaughrean with the European Space Agency, thanks so much.

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