Once in million years: Comet buzzing Mars on Sun

October 16, 2014 by Marcia Dunn
This March 27, 2014 image provided by NASA, ESA, and J.-Y. Li shows comet C/2013 A1, also known as Siding Spring, as captured by Wide Field Camera 3 on NASA's Hubble Space Telescope. (AP Photo/NASA, ESA, J.-Y. Li)

(AP)—The heavens are hosting an event this weekend that occurs once in a million years or so.

A comet as hefty as a small mountain will pass mind-bogglingly close to Mars on Sunday, approaching within 87,000 miles (140,006 kilometers) at a speed of 126,000 mph (202,767 kph).

NASA's five robotic explorers at Mars—three orbiters and two rovers—are being repurposed to witness a comet named Siding Spring make its first known visit to the inner solar system. So are a European and an Indian spacecraft circling the red planet.

The orbiting craft will attempt to observe the incoming iceball, then hide behind Mars for protection from potentially dangerous dusty debris in the comet tail.

Shielded by the Martian atmosphere, the Opportunity and Curiosity rovers may well have the best seats in the house, although a dust storm on Mars could obscure the view.

"We certainly have fingers crossed for the first images of a comet from the surface of another world," said NASA program scientist Kelly Fast.

Spacecraft farther afield, including the Hubble Space Telescope, already are keeping a sharp lookout, as are ground observatories and research balloons.

"We're getting ready for a spectacular set of observations," said Jim Green, head of NASA's planetary science division.

Named for the Australian observatory used to detect it in January 2013, Siding Spring will approach Mars from beneath and zoom right in front Sunday afternoon, Eastern Time.

On Earth, the best viewing, via binoculars or telescope, will be from the Southern Hemisphere—South Africa and Australia will be in prime position. In the Northern Hemisphere, it will be difficult to see Siding Spring slide by Mars.

The comet—with a nucleus estimated to be at least a half mile (.8 kilometer) in diameter—hails from the Oort Cloud on the extreme fringe of the solar system. It formed during the first million or two years of the solar system's birth 4.6 billion years ago and, until now, ventured no closer to the sun than perhaps the orbits of Jupiter, Saturn, Uranus or Neptune. It comes around every one or more million years.

It will be the first Oort Cloud comet to be studied up close in detail.

For comparison, the flyby distance of 87,000 miles (140,006 kilometers) is about one-third of the way from here to the moon. Siding Spring's tail could extend from Earth all the way to our moon. Its gaseous coma, the fuzzy head surrounding the nucleus, might stretch halfway to the moon.

No comet has come anywhere near this close to Earth in recorded history.

"We can't get to an Oort Cloud comet with our current rockets ... so this comet is coming to us," said Carey Lisse, senior astrophysicist at Johns Hopkins University's applied physics laboratory.

By studying Siding Spring's composition and structure, scientists hope to learn more about how the planets formed, according to Lisse. Scientists also are keen to spot any changes to the comet or Mars due to the close approach. NASA's newly arrived Maven spacecraft, for instance, will compare the upper atmosphere before and after it passes.

"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."

Scientists initially worried the spacecraft orbiting Mars would be at considerable risk from the comet's massive trail of dust.

The nucleus itself poses no danger of impact. But the particles in the tail, hurtling through space at 126,000 mph (202,767 kph) could fry electronics, puncture fuel lines, or destroy computers, transmitters or other vital spacecraft parts.

As Siding Spring's path became clearer, the threat level was deemed minimal. Still, space agencies are taking no chances. They're employing the "duck and cover" strategy.

NASA's three orbiters—Mars Odyssey, Mars Reconnaissance Orbiter and newcomer Maven—will be behind the at the time of peak danger. That's a 20-minute-or-so period approximately 1½ hours after the closest approach by the 's nucleus.

The European Space Agency also shifted the orbit of its Mars Express as did India for its Mars Orbiter Mission, or MOM, the country's first interplanetary spacecraft that, like NASA's Maven, arrived last month.

The precautions are prudent, said University of Maryland senior research scientist Tony Farnham, who led a hazard-analysis team.

"Comets are complex beasts and don't always live up to our predictions," Farnham said in an email Wednesday. "If you don't want surprises, then don't study comets."

It will take at least a few days to obtain and analyze the best spacecraft data; but images made from Earth should be forthcoming pretty quickly.

Siding Spring should pass closest to the sun six days after its Mars flyby, then swing back out, bidding goodbye, for at least another million years.

Explore further: NASA prepares its science fleet for Oct. 19 Mars comet encounter

More information: mars.nasa.gov/comets/sidingspring/

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17 comments

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axemaster
5 / 5 (7) Oct 16, 2014
Just for anyone who's interested, 126,000 mph is 56km/s.
teslaberry
2.3 / 5 (9) Oct 16, 2014
this things velocity is so fast and it is so massive, that it would have made the most spectacular wedding with the martian surface. alas, the engagement was called off last year only weeks after the courtship began. you can imagine i was devastated when i heard that news. (to boot, sun approaching isohn provided no light show as it approached the sun, so much for teasing! )

so now , we watch these two lovers do their last dance and on they go.

i'm still hoping a major cosmological impact of mars mercury or venus or of any moon occurs before i die. shoemaker levy was big, but the fireworks were obscured by thousands of miles of cloud cover. but please lord of the asteroids, SPARE THE EARTH!
verkle
Oct 16, 2014
This comment has been removed by a moderator.
Vietvet
4.2 / 5 (10) Oct 16, 2014
If these such events are already recorded in the brief 50 year timespan that we have been viewing planets in detail, I would venture to suggest that they happen much more often than every 1 million years.


Your comment is based on your "the world is 6,000 years old" beliefs.
Steve 200mph Cruiz
4.5 / 5 (8) Oct 16, 2014
If these such events are already recorded in the brief 50 year timespan that we have been viewing planets in detail, I would venture to suggest that they happen much more often than every 1 million years.


It's statistics Verkle, they've had your mundane questions figured out decades ago.
cantdrive85
1.5 / 5 (8) Oct 16, 2014
"Comets are complex beasts and don't always live up to our predictions," Farnham said in an email Wednesday. "If you don't want surprises, then don't study comets."


Sounds like a new theory is justified.
Steve 200mph Cruiz
4.5 / 5 (8) Oct 16, 2014
"Comets are complex beasts and don't always live up to our predictions," Farnham said in an email Wednesday. "If you don't want surprises, then don't study comets."


Sounds like a new theory is justified.


Comets are real, they are surprising in that they are analogous to finding an Egyptian artifact: Its archeology of the solar system. History in Chemistry, our understanding of fusion in stars explains how our solar system formed. As our understanding or our solar system helps explain the fusions of stars.

yep
1.6 / 5 (7) Oct 16, 2014
This video on Rosetta is a great history lesson, as well as primer for a modern understanding of solar system theory, and Phys.org gives a nice cameo appearance!
http://www.youtub...osK4tWYA
HannesAlfven
1.6 / 5 (7) Oct 16, 2014
Re: "If you don't want surprises, then don't study comets."

The repeated surprise is repeatedly surprising.
Vietvet
5 / 5 (4) Oct 17, 2014
"This video on Rosetta is a great history lesson, as well as primer for a modern understanding of solar system theory,----"

Great for some belly laughs!
antialias_physorg
5 / 5 (5) Oct 17, 2014
For comparison, the flyby distance of 87,000 miles (140,006 kilometers) is about one-third of the way from here to the moon.

For comparison: Phobos (the closer one of Mars' moons) has an average distance of 6000km to the surface.
verkle
Oct 17, 2014
This comment has been removed by a moderator.
Scroofinator
1 / 5 (4) Oct 17, 2014
that it would have made the most spectacular wedding with the martian surface


I don't think it can still be ruled out. According to my theory the comet will come closer then GR based orbital mechanics says it will.

Also, I wonder if there will be an added drag effect from the coma interacting with the Martian atmosphere? It's supposed to double the hydrogen content of the atmosphere for hours.

"The coma of the comet is projected to more than double the amount of hydrogen in the high atmosphere for a period of several tens of hours and to slightly warm it by about 30 K for a few hrs"
http://en.wikiped.../2013_A1
Vietvet
5 / 5 (5) Oct 17, 2014
Vietvet, everyone's comments are shaped by their worldviews. Why do you have to continually make personal attacks who doesn't subscribe to your worldview?

Grow up!



My world view is based on evidence, your's is based on faith. Just admit it.
OZGuy
5 / 5 (2) Oct 18, 2014
@ verkle
Hypocrite .. you malign anyone that presents any evidence that contradicts creationism.
Bob Osaka
not rated yet Oct 20, 2014
And just like Hyakutake , C2013 A1 Siding Spring came out of the darkness with little to no warning. Hyakutake's closest pass to Earth coming just two months after its discovery. Can't really say the space agencies have sprung into action on this one either, all advertising to the contrary. No stardust collection, no impactor missions, no landings attempted and everyone acknowledges this is an Oort cloud object, a once in a million year chance. Budget constraints, maybe next time.
antialias_physorg
not rated yet Oct 20, 2014
a once in a million year chance.

Since they do 'come out of the darkness' on occasion it's a bit better than a one-in-a-million-year chance.
Yes: it would be nice to have a mission to each and every one of these. But there are many more objects out there than we can afford to visit. Unless and until we initiate our own von Neumann probes (more correctly "Astrochickens") I don't see us getting a full picture of every rock that's out there.

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