Mars Awaits Visit From Comet Siding Spring On Sunday

Chuck Bednar for redOrbit.com – Your Universe Online
A mountain-sized comet called C/2013 A1 will pass within 87,000 miles of Mars on Sunday afternoon, bringing it closer to the Red Planet than the Earth is to the moon and nearer than any comet in the past one million years.
C/2013 A1, also known as Comet Siding Spring in honor of the Australian observatory where it was first discovered in January 2013, is expected to come closest to Mars at 2:27pm EDT Sunday afternoon, said ABC News reporter Alyssa Newcomb. At that time, it will be traveling at speeds of approximately 34 miles per second, she added.
“We’re going to observe an event that happens maybe once every million years,” Jim Green, director of NASA’s planetary science division, said earlier this month, according to NBC News. “This is an absolutely spectacular event.”
The nucleus of the comet is believed to be between one-half a mile and five miles wide, and the gas cloud that surrounds the nucleus is approximately 12,000 miles across, said Deborah Netburn of the Los Angeles Times. Experts report that C/2013 A1 most likely originated in the Oort Cloud, a giant swarm of icy material believed to have been left over from the formation of the solar system, more than 4.5 billion years ago.

Scientists note that the comet’s flyby will be best observed using binoculars or telescopes by people living in the Southern Hemisphere – especially residents of South Africa and Australia. For the rest of us, NASA satellites and spacecraft will be keeping a close eye on Sunday’s events, capturing images of and data about the comet and the planet as it is soaring past.
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Among the things that scientists with the US space agency will be looking for is whether or not the comet’s particles will have any impact on the thin atmosphere of Mars, and whether or not its tail will damage any of the spacecraft currently orbiting the Red Planet, according to Los Angeles Times and NBC News reports.
“In all, a dozen spacecraft and the Curiosity and Opportunity rovers on Mars will have a chance to observe and document Siding Spring’s visit,” said CNET’s Eric Mack. “NASA’s Mars Odyssey orbiter, Mars Reconnaissance Orbiter (MRO) and Mars Atmosphere and Volatile EvolutioN (MAVEN) are taking measures to hide behind the far side of the Red Planet as Siding Spring passes, enveloping Mars in a cloud of potentially dangerous dust and particles traveling at high enough speeds to act like a bullet should they impact part of an orbiter.”
NASA reported earlier this month that the period of greatest risk to the MRO, MAVEN and the other spacecraft in the area would begin approximately 90 minutes before the closest approach of the comet’s nucleus and would only last for roughly 20 minutes, during which time the planet would come closest to its widening dust trail.

“The hazard is not an impact of the comet nucleus itself, but the trail of debris coming from it,” said Rich Zurek, chief scientist for the Mars Exploration Program at NASA’s Jet Propulsion Laboratory (JPL). “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.”
Before, during and after C/2013 A1’s flyby, the Opportunity, Curiosity and the Mars orbiters will gather data about the size, rotation and activity of the comet’s nucleus, as well as the gas composition and variability of the coma surrounding the nucleus and the size and distribution of dust particles in the comet’s tail, NASA said. MAVEN is expected to have an especially good chance to study the comet and how it interacts with Mars’ upper atmosphere.
In addition, both Earth and space-based telescopes (including Hubble) and NASA space observatories (such as Kepler, Swift, Spitzer and Chandra) will be tracking the event, and the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) has been and will continue to be imaging the comet over the weekend. The agency said that updates and images would be posted at their website both prior to and following the flyby event.
“Think about a comet that started its travel probably at the dawn of man and it’s just coming in close now,” Carey Lisse, a senior astrophysicist at the Johns Hopkins University Applied Physics Laboratory, said during a NASA news briefing about Comet Siding Spring several days ago, according to CNET. “And the reason we can actually observe it is because we have built satellites and rovers. We’ve now got outposts around Mars.”
“If we study the comet – its composition, its structure – it will tell us a lot about how we think maybe the planets were formed,” he added, according to NBC News and Space.com. “We can’t get to an Oort Cloud comet with our current rockets. These orbits are very long and extended – and at very great velocities… It’s a free flyby, if you will, and that’s a very fantastic event for us to study.”
Officials at the European Space Agency are also prepared for the comet’s close approach to the Red Planet. According to an official statement, the Mars Express orbiter “will have a frontrow seat on Sunday when Comet Siding Spring grazes the Red Planet, skimming past at a little more than a third of the Moon’s distance from Earth.”

Image Above Credit: NASA/JPL-Caltech
Related Reading:
> NASA Prepares its Science Fleet for Oct. 19 Mars Comet Encounter
> VIDEO: Comet Siding Spring: A Close Encounter With Mars
> VIDEO: ScienceCasts: Colliding Atmospheres – Mars Vs Comet Siding Spring
> Atmospheres Of Mars And Comet Siding Spring May Collide In October
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