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NASA ScienceCasts - Colliding Atmospheres - Mars vs Comet Siding Spring

NASA's Martian fleet gears up for comet encounter of a lifetime

Scott Sutherland
Meteorologist/Science Writer

Thursday, October 9, 2014, 4:56 PM - On October 19th, NASA's fleet of spacecraft orbiting around Mars, and its robot rovers on the surface, will be rewarded for all their hard work with a rare treat. They will have the planetary equivalent of a front-row seat for when Comet 2013 A1 (Siding Spring) makes an extremely close flyby past Mars!

Comet 2013 A1, or Comet Siding Spring, was discovered on January 1st, 2013, by astronomers working at the Siding Spring Observatory in Australia. As they tracked the path of the comet, two things became clear to the astronomers: 1) 2013 A1 was very likely a first-time visitor to the inner solar system, meaning that it has spent most of its time far, far out in the Oort Cloud that surrounds the solar system, and it likely contains materials that have been untouched since the solar system formed, and 2) this comet was going to come very close to the planet Mars.

In fact, for the first few months of observations, astronomers couldn't rule out the possibility that the comet may actually hit Mars!

Now, after over 21 months of observations, they are confident that the comet's nucleus - the mass of ice and rock and dust at the centre of the coma - is going to fly by at less than 140,000 kilometres away (a little over one-third the distance between the Earth and the Moon). So, that's going to be a clean miss for the nucleus, but maybe not for other parts of the comet.

"The hazard is not an impact of the comet nucleus itself, but the trail of debris coming from it," said Rich Zurek, Mars Exploration Program chief scientist at NASA's Jet Propulsion Laboratory (JPL), according to a NASA statement. "Using constraints provided by Earth-based observations, the modeling results indicate that the hazard is not as great as first anticipated. Mars will be right at the edge of the debris cloud, so it might encounter some of the particles - or it might not."

If particles from the comet do interact with Mars' atmosphere, it could produce meteor showers visible from both space and the surface, and it could spark auroras over those spots on the planet where Mars' weak, regional magnetic fields pierce through the surface. Also, just to be safe, the spacecraft in orbit of the planet will be performing a 'duck & cover' maneuver to keep the planet between them and the comet during the most dangerous point of the flyby. This is just to prevent these spacecraft from being 'sandblasted' by cometary debris particles.

Credit: NASA/JPL-Caltech

NASA is really pulling out all the stops for this once-in-a-lifetime event, too.

16 different NASA missions will be watching closely. Some, like Hubble, Spitzer, SOHO, Kepler, NeoWISE, Chandra and Swift will watch from here in Earth's neighborhood. Others will be observing from nearly on the other side of the Sun from us. The front-row seats will be occupied by the Mars Reconnaissance Orbiter (MRO), Mars Odyssey, MAVEN and Mars Express, in orbit of the planet, and the Curiosity and Opportunity rovers on the surface. They will not only capture the best images of the comet, but the latest one to arrive - MAVEN - is uniquely equipped to get the best look at the interaction between the coma and Mars' atmosphere.

Credit: NASA

"This is a cosmic science gift that could potentially keep on giving, and the agency’s diverse science missions will be in full receive mode," John Grunsfeld, astronaut and associate administrator for NASA’s Science Mission Directorate, said in a NASA statement about the Comet Siding Spring flyby. "This particular comet has never before entered the inner solar system, so it will provide a fresh source of clues to our solar system's earliest days."

As a prelude to this encounter, NASA is hosting a special social media gathering at the Jet Propulsion Laboratory in Pasadena, Calif., on Monday, October 13, and The Weather Network will be on-hand to report live from the event. 50 attendees will be giving a special, behind-the-scenes tour of JPL, to see portions of the facility that are typically closed to the public, and to interact with mission specialists and scientists. This includes a special speaker presentation to discuss not only Siding Spring, but another comet mission - the Rosetta spacecraft and its plan to put a lander (Philae) on the surface of Comet 67/P Churyumov-Gerasimenko on November 12. Follow @ScottWx_TWN on twitter for live-tweets from JPL's public Open House over the weekend and the NASA Social event on Monday, and tune in to NASA TV at 2 pm Pacific (5 pm Eastern) on Monday, Oct 13 to watch the presentation live.

Ahead of that, though, NASA held a press conference on Thursday, to describe their preparations for the Siding Spring encounter and to answer questions from the public and the media. This is presented in the video below:

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