[no sound] [no sound] >>Interviewer: Mars is facing a close call on Sunday, October 19th when a rare comet will pass by at an extremely close distance, and here to tell us more about Comet Siding Spring is NASA scientist Dr. Jared Espley. Thank you for joining us. >>JARED: Good morning. >>INTERVIEWER: So what is a comet and why do we study them? >>JARED: Most people when they think of comets, think of these objects that they can look up into the night sky, these beautiful objects that have these long, arching tails that come out behind them. From our modern observations, we actually know that these are chunks of ice and rock, dirty snowballs, that are the leftovers of the beginnings of the solar system. They are ancient relics of the beginnings of the planets, and potentially the beginnings of life. So generally, they reside in the outer reaches of the solar system, and occasionally something nudges them into the inner solar system, where they start to heat up, and they get this cloud of gas that is around the comet, and that's what you can see when you look up at the night sky. >>INTERVIEWER: What makes Comet Siding Spring so special, and will we be able to see it? >>JARED: Comet Siding Spring, like most of its siblings, resided in the outer reaches of the solar system. But about a million years ago, it started to drift slowly and invisibly, at first, into the inner solar system. When we humans first noticed it about a year ago, we realized it was on a near direct collision course with Mars. And so that nucleus, that central chunk of ice and rock would just barely miss the planet. But the gas cloud will in fact envelop the planet. And so that will give us a fantastic opportunity to do science when the comet comes by, and swallows Mars on Sunday for a few hours. >>INTERVIEWER: How will NASA study Comet Siding Spring from Mars? >>JARED: NASA's going to use a variety of telescopes on the ground observatories to look up, and also telescopes in orbit at Earth like Hubble, but most especially are going to use the spacecraft at Mars. The rovers that are on the surface to look up at the night sky, the Martian night sky, and also the spacecraft that are in orbit around the planet. And in particular I'm really excited about a mission called MAVEN that by really good luck is going to arrive at Mars, just, has just arrived, and so it is there in perfect opportunity to be able to study the comet and how it will be potentially heating up and potentially temporarily blowing away the Martian atmosphere, which is what MAVEN is designed to do, so it's a fantastic opportunity for science. >>INTERVIEWER: Is the comet dangerous, and will the satellites orbiting Mars be damaged? >>JARED: So the dust, which is distinct from the gas cloud that I mentioned before, the dust is moving at about a hundred thousand miles per hour. And so yes, if that were to hit a spacecraft at Mars, that would be a really sad day for that spacecraft. However, we very carefully modeled the dust, and we think that it's going to just barely miss the planet, and therefore the satellites that are in orbit around the planet. Nonetheless, we're going to try to time the orbit of our spacecraft so that we're hiding behind the planet when the dust tail comes by, so that we'll be protected by the planet from the dust. And so, we'll be able to avoid all the danger, and be able to do all the awesome science that are a result. >>INTERVIEWER: Sounds good, where can we learn more? >>JARED: You can learn more at mars.nasa.gov, there you can learn about all the Mars program missions there, and also about the Comet Siding Spring encounter specifically. >>INTERVIEWER: Dr. Jared Espley from NASA Goddard Space Flight Center, thank you very much. >>JARED: Thank you. [beep beep...] [beep beep... beep beep... beep beep...]