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[no sound] >>Interviewer: Mars is facing a close call

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

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an extremely close distance, and here to tell us more about Comet

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Siding Spring is NASA scientist Dr. Jared Espley. Thank you for joining us.

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>>JARED: Good morning. >>INTERVIEWER: So what is a comet and why do we study them?

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>>JARED: Most people when they think of comets, think of these objects that they can

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look up into the night sky, these beautiful objects that have these long, arching

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tails that come out behind them. From our modern observations, we actually

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know that these are chunks of ice and rock, dirty snowballs,

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that are the leftovers of the beginnings of the solar system. They are

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ancient relics of the beginnings of the planets, and potentially the beginnings of life.

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So generally, they reside in the outer reaches of the solar system, and occasionally something

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nudges them into the inner solar system, where they start to heat up, and they get this cloud of

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gas that is around the comet, and that's what you can see when you

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look up at the night sky. >>INTERVIEWER: What makes Comet Siding Spring

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so special, and will we be able to see it? >>JARED: Comet

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Siding Spring, like most of its siblings, resided in the outer reaches

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of the solar system. But about a million years ago, it started to drift slowly

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and invisibly, at first, into the inner solar system.

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When we humans first noticed it about a year ago, we realized it was on a near direct collision course

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with Mars. And so that nucleus, that central chunk of ice and rock

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would just barely miss the planet. But the gas cloud will in fact envelop

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the planet. And so that will give us a fantastic opportunity to do science when

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the comet comes by, and swallows Mars on Sunday for a few

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hours. >>INTERVIEWER: How will NASA study Comet Siding Spring from Mars?

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>>JARED: NASA's going to use a variety of telescopes on

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the ground observatories to look up, and also telescopes in orbit at Earth

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like Hubble, but most especially are going to use the spacecraft at Mars.

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The rovers that are on the surface to look up at the night sky, the Martian night sky,

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and also the spacecraft that are in orbit around the planet. And in particular

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I'm really excited about a mission called MAVEN that by really good luck is

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going to arrive at Mars, just, has just arrived, and so it is there

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in perfect opportunity to be able to study the comet and how it

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will be potentially heating up and potentially temporarily blowing away the Martian

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atmosphere, which is what MAVEN is designed to do, so it's a fantastic opportunity for science.

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

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Mars be damaged? >>JARED: So the dust, which is

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distinct from the gas cloud that I mentioned before, the dust is moving at about a hundred thousand

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miles per hour. And so yes, if that were to hit a spacecraft

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at Mars, that would be a really sad day for that spacecraft. However, we

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very carefully modeled the dust, and we think that it's going to just barely miss the planet,

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and therefore the satellites that are in orbit around the planet. Nonetheless, we're

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going to try to time the orbit of our spacecraft so that we're hiding behind the planet

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when the dust tail comes by, so that we'll be protected by the planet

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from the dust. And so, we'll be able to avoid all the danger, and be able to do all

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the awesome science that are a result. >>INTERVIEWER: Sounds good, where can we

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learn more? >>JARED: You can learn more at mars.nasa.gov,

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there you can learn about all the Mars program missions there, and also

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about the Comet Siding Spring encounter specifically.

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>>INTERVIEWER: Dr. Jared Espley from NASA Goddard Space Flight Center, thank you very much.

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>>JARED: Thank you. [beep beep...]

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