On Sunday, a "once in a million years" event will dazzle the inner solar system. Comet Siding Spring will make a heart-stopping close flyby of the Red Planet, giving our Martian armada of robotic explorers a ring-side view of the spectacle.
NEWS: Mars Missions Preparing for Thrilling Comet Close Shave
C/2013 A1 (Siding Spring) was discovered on Jan. 3, 2013, by Robert McNaught at the Siding Spring Observatory in Australia and, originally, astronomers were excited for the possibility that the half mile-wide lump of ice and rock might actually hit Mars. But since its orbital trajectory was tracked and forecast, astronomers realized that it would miss - but only by a hair's breadth (cosmically speaking).
If the comet did hit, NASA's Mars rovers Curiosity and Opportunity would be at risk by the impact, but the opportunity of seeing a planetary impact of this magnitude would have been historic and scientifically profound. But rather than preparing for the bittersweet eventuality of a cometary impact, the world's space agencies are now preparing for the mother of all remote observation campaigns when Siding Spring swings past the planet at a close approach of less than 87,000 miles.
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There are no less than 7 missions currently in orbit around and roving on Mars: NASA's Mars Reconnaissance Orbiter (MRO), Mars Odyssey and the Mars Atmosphere and Volatile Evolution (MAVEN), the European Space Agency's Mars Express (MEX) and Indian Mars Orbiter Mission (MOM) are all in orbit. NASA's Curiosity and Opportunity rovers are on the Martian surface. For months, the missions' science teams have been preparing for this close encounter.
For example, while optimizing the time they will image the comet, NASA has altered the orbits of their trio of satellites so they will be shielded behind Mars when exposure to high-velocity comet particles could pose a risk.
"The hazard is not an impact of the comet nucleus, but the trail of debris coming from it," said Rich Zurek, chief scientist for the Mars Exploration Program at NASA's Jet Propulsion Laboratory in Pasadena, Calif.. "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."
On the other hand, according to a European Space Agency news release today (Oct. 17), Mars Express will be operating "substantially normally," since assessments of cometary activity have lowered the risk of orbital hardware getting damaged.
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"We designed a special mode for Mars Express that would minimize any risk due to impacts with cometary particles," said MEX Spacecraft Operations Manager Michel Denis. "This included turning off all instruments and non-essential onboard systems, and turning the spacecraft so as to use the large high-gain antenna as a shield."
As Siding Spring approaches, it seems ESA will not be using this contingency plan and instead opting for "normal" operations to use the orbiter to capture some dazzling high-resolution imagery of the comet's nucleus.
"Most interestingly, we may also obtain images of cometary particles - meteors - burning up in the Martian atmosphere, allowing an in-depth comparison of meteor science between Earth and Mars," said MEX project scientist Håkan Svedhem.
Our Martian explorers will also be getting some help from an observation campaign on Earth, too. The Hubble Space Telescope, which is in Earth Orbit, will be staring Mars-ward on Sunday, as will a set of balloon-borne telescopes.
PHOTO: Hubble Zooms-in on Mars-Buzzing Comet Siding Spring
"We're getting ready for a spectacular set of observations," said Jim Green, head of NASA's planetary science division.
This is thought to be Siding Spring's first foray into the inner solar system. Originating from the Oort Cloud -- a hypothetical ‘shell' surrounding our solar system around a light-year distant full of primordial chunks of ice left over from the formation of our sun and planets -- the comet will make its first ‘deep dive' close to the sun. And it just so happens that the comet will fly past the second most populated planet in the solar system - albeit populated by robots.
"The best estimate of the maximum distance of Siding Spring is 60,000 times Earth's distance from the sun - almost exactly a light-year," said Håkan. "This makes it an extraordinary comet. It has most likely never been close to the sun before."
"We can't get to an Oort Cloud comet with our current rockets ... so this comet is coming to us," astrophysicist Carey Lisse, at Johns Hopkins University's Applied Physics Laboratory, told the Associated Press. "Think about a comet that started its travel probably at the dawn of man and it's just coming in close now," Lisse said. "And the reason we can actually observe it is because we have built satellites and rovers. We've now got outposts around Mars."
Our insatiable desire to explore comets is motivated by our need to understand where we came from. These ancient icy bodies contain not only information about the chemicals that built our sun and planets, they also hold the key to where life may have come from. The prebiotic compounds comets contain and the conditions in which they were formed provide us with a time capsule to the solar system's deep past... and it just so happens the Cosmos is delivering a time capsule, packaged nearly 5 billion years ago, that will be opened by our Mars robot emissaries on Sunday.
Sources: ESA, NASA, AP