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NASA prepares Mars orbiters for comet close encounter

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July 28, 2014

Comet C/2013 A1 will pass Mars ten times closer than any observed comet has passed the Ear...

Comet C/2013 A1 will pass Mars ten times closer than any observed comet has passed the Earth (Image: NASA/Swift/D. Bodewits (UMD), DSS)

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In October, Mars will encounter comet C/2013 A1 Siding Spring, which will come closer to the Red Planet than any recorded comet has passed to Earth. This spectacular event isn't just an astronomical curiosity, it’s also a potential hazard to NASA’s armada of orbiting explorers, so the space agency is taking steps to protect them from damage by the cosmic visitor.

Comet C/2013 A1 Siding Spring was discovered in 2013 by Robert H. McNaught at Siding Spring Observatory. It’s unusual because its orbit is so elongated that this is the first time it’s visited the inner solar system in several million years. That would be enough to peak astronomers’ interest, but early calculations indicated that it would pass so close to Mars that it could result in a once in a million years impact on the Red Planet.

As Siding Spring approached Mars, new observations and calculations proved that the comet wouldn't strike, but its nucleus would pass within 82,000 mi (132,000 km) of the planet at a relative speed of 35 mi/sec (56 km/sec, 126,000 mph, 200,000 km/h) on October 19. This is only a tenth of the distance of the closest observed comet encounter with Earth.

Diagram showing the passage of comet C/2013 A1 (Image: NASA/JPL-Caltech)

While the nucleus of the comet won’t hit, Mars will pass through its tail. This tail is made up of gas so tenuous that it’s almost a vacuum, but it also includes solid particles of various sizes down to 0.5 mm that could destroy one of the orbiters like a bullet going through a smartphone

NASA is now preparing its Mars Odyssey and Mars Reconnaissance Orbiter (MRO) orbiters for the encounter, as well as the approaching Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft, scheduled to arrive a month before Siding Spring, and its two surface rovers Opportunity and Curiosity. It’s also configuring the craft to take advantage of the event to take a closer look at the passing comet.

The agency solicited three computer models of the comet’s passing from the University of Maryland in College Park, the Planetary Science Institute in Tucson, Arizona, and the Jet Propulsion Laboratory (JPL) in Pasadena, California. These were used for calculating how best to protect the orbiters.

NASA is putting all three of the orbiters through course maneuvers that will place them on the opposite side of the planet during the most dangerous 20 minutes of the encounter, which will occur 90 minutes after Siding Spring makes its closest approach. It will be during this period that debris from the comet will reach Mars.

Comet C/2013 A1 as seen by the Hubble telescope (Image: NASA, ESA, and J.-Y. Li (Planetary...
Comet C/2013 A1 as seen by the Hubble telescope (Image: NASA, ESA, and J.-Y. Li (Planetary Science Institute) )

According to the space agency, the MRO made a course correction on July 2, and the Mars Odyssey will do the same on August 27. Meanwhile, MAVEN will arrive in Mars orbit on September 21, after which it will make a protective maneuver on October 9. Though the Martian atmosphere is extremely thin, NASA says that it’s thick enough to keep the two rovers out of danger by burning up any comet particles.

In a cosmic example of making lemonade out of unexpected lemons, NASA will use the instruments on the various spacecraft to observe Siding Spring’s passing and its effects on the Martian atmosphere as it encounters the tail. In addition, the rovers’ cameras will record the comet’s passing and any meteors burning up in the Martian atmosphere. NASA hopes that the very long orbit of the comet will provide new insights into the early history of the Solar System.

Source: NASA

About the Author
David Szondy David Szondy is a freelance writer based in Monroe, Washington. An award-winning playwright, he has contributed to Charged and iQ magazine and is the author of the website Tales of Future Past.   All articles by David Szondy
4 Comments

I really hope the rovers/orbiters will get some amazing shots of this event.

Brian Mcc
28th July, 2014 @ 07:37 pm PDT

If this comet had hit Mars it would have had some major effects on Mars climate. This may have been beneficial to human exploration and colonisation by temperature rises, melting of ice caps , thickening of atmosphere.

If we are planning on colonising Mars we should have plans to take advantage of comets like this, eg using lasers to cause the comet to hit.

Stephen Colbourne
28th July, 2014 @ 08:46 pm PDT

i had been tracking the reports about this comet ever since it was first announced.

within 6 weeks or so of its first public announcement they had refined their observations to be fairly certain it would not hit mars. i was sorely disspapointed.

had this object hit mars, it would have been the first major astronmical body to have been observed hitting a solid planet surface. martian atmosphere is thick enough to observe, but thin enough to be de-minimus.

furthermore , when it comes to the ONLY other major observed collision , that of shoe-maker levy, the telescopes and sattelites observing the collision were far less powerful and did not have the benefit of todays digital processors.

furthemore, most importantly, the shoemaker-levy hit jupiter---a gaseous liquid like atmosphere , which obscured most of the impacts affects under the depths of the opaque surface. nontheless, the results of this impact are still scrutinized for new information to this day.

we really have NO actual observed large impacts on a solid body to analogize to earth. while it is true that a large and fast hard impactor would hit earth most likely in the oceans, it COULD hit solid ground. furthermore, small impacts on places like the moon do not provide good analogies for what coudl happen to earth. on an asthetic level they are also less interesting, as mars has many dynamic geological and hydrological or carbonlogical processes on its surface and shallow subsurface. as a result, there would be far more dynamic processes to observe if something sizeable hit mars.

what a shame. it would have been the astonomical event of a lifetime. and people of my age---34, will probably never get to witness something like this extraodinarily rare potentially event.

perhaps if we are lucky, or able to steer a sizeable asteroid ( no easy task) something big will hit venus or mars in the future......

zevulon
28th July, 2014 @ 10:01 pm PDT

I wanted the impact event.

Slowburn
29th July, 2014 @ 09:57 am PDT
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