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[no sound] >>INTERVIEWER: Mars is facing a

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close call on Sunday, October 19th, when a rare comet will pass by

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at an extremely close distance. And here to tell us more about Comet

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Siding Spring, out of NASA's Goddard Space Flight Center in Greenbelt,

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Maryland, is Planetary Science Division Director Dr. Jim Green.

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Thank you for joining us. >>JIM: Thank you. >>INTERVIEWER: What is a comet and why

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do we study them? >>JIM: Well comets have been looked at for

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millions of years here on Earth by humans and they're just beautiful

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objects. They're bright with long tails. And

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when we look inside them, we see that the nucleus is a dirty snowball,

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made up of ices and rock, that as it gets close to the Sun,

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produces these long, beautiful tails. These comets were

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actually born in the early part of our solar system. They're

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older than the planet Earth. And interactions with the Earth,

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they're throwing these comets out for millions of miles, and now

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we have a wonderful opportunity to see Siding Spring come by

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into the inner solar system. >>INTERVIEWER: So what makes Comet Siding

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Spring so special, and will we be able to see it here from Earth?

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>>JIM: Well Siding Spring is very special because it's coming in from

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the far reaches of our solar system. It's going to pass right

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in front of Mars. Mars will be bathed

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in cometary material. Now what's really great about

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the comet is we'll have assets like Opportunity

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and Curiosity on the surface observing the comet.

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In addition to that, we're going to have our spacecraft, like MAVEN,

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and Mars Reconnaissance Orbiter, and Mars Odyssey, making

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observations of the comet as it flies by.

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>>INTERVIEWER: Is this comet dangerous, and will the satellites orbiting Mars

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be damaged? >>JIM: The comet is not dangerous, in the sense

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that our spacecraft will be on the other side of the

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planet Mars when the dust tail goes by. So we've

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phased them just right so that they're out of danger. And this

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is very important because it also enables them to observe the comet

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before, during, and after this fabulous encounter.

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>>INTERVIEWER: Sounds great. Where can we learn more? >>JIM: For more

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information, please go to mars.nasa.gov.

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>>INTERVIEWER: Great, thank you very much, Dr. Jim Green. >>JIM: You're welcome, thank you.

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