Could Comet C/2013 A1 impact Mars in 2014?

[Ghostrider]

I bow to your superior LOTR knowledge.

My friends... You bow to no one.

 

[RGClark]

Assuming it is to miss Mars by 37,000 km what would be the delta-V needed to nudge it to impact Mars?

Bob Clark

 

[MaverickSawyer]

Depends on how far in advance you nudge it.

 

[dgatsoulis]

:hesaid:

A few numbers:

Today = 3 m/s
In one year = 16 m/s
One month before periareion = 111 m/s
One day before periareion = 3325 m/s
6 hours before periareion = 13300 m/s

Source: Orbiter

 

[RGClark]

:hesaid:

A few numbers:

Today = 3 m/s
In one year = 16 m/s
One month before periareion = 111 m/s
One day before periareion = 3325 m/s
6 hours before periareion = 13300 m/s

Source: Orbiter

Thanks for that. This might not be purely of academic interest. Already we've seen two Earth encounters whose likelihood together was one in hundreds of millions.

This comet to make a close encounter to Mars is huge. To put it perspective it dwarfs the asteroid that destroyed the dinosaurs. Such close encounters to any of the terrestrial planets must be very rare.

For instance the puny, in comparison, asteroid 2012 DA14 would be expected to get so close to the Earth once in 40 years. That such a large comet would get so close to Mars must be much rarer than this. So the chance is less than 1 in 40 in a year. Say it happens for either of two planets; that's a chance of less than 1 in 20 in a year. Say then it happens within a 2 year period; that's 1 chance in 10.

Now the chance of the three encounters occurring within such a close time span is greater than one in several billion. The unlikelihoods begin piling up greater and greater.

Then we are left with the disturbing possibility there is a physical phenomenon causing these large, close encounters. And the possibility arises there is another large, close encounter to the Earth that may be upcoming.

It would really become important to know then not what's the delta-v needed to turn a close miss to an impact, but in fact the reverse.


Bob Clark

 

[BruceJohnJennerLawso]

Thanks for that. This might not be purely of academic interest. Already we've seen two Earth encounters whose likelihood together was one in hundreds of millions.

This comet to make a close encounter to Mars is huge. To put it perspective it dwarfs the asteroid that destroyed the dinosaurs. Such close encounters to any of the terrestrial planets must be very rare.

For instance the puny, in comparison, asteroid 2012 DA14 would be expected to get so close to the Earth once in 40 years. That such a large comet would get so close to Mars must be much rarer than this. So the chance is less than 1 in 40 in a year. Say it happens for either of two planets; that's a chance of less than 1 in 20 in a year. Say then it happens within a 2 year period; that's 1 chance in 10.

Now the chance of the three encounters occurring within such a close time span is greater than one in several billion. The unlikelihoods begin piling up greater and greater.

Then we are left with the disturbing possibility there is a physical phenomenon causing these large, close encounters. And the possibility arises there is another large, close encounter to the Earth that may be upcoming.

It would really become important to know then not what's the delta-v needed to turn a close miss to an impact, but in fact the reverse.


Bob Clark

I dont know, I really doubt the statistics are any higher than usual for near misses. Its more likely to be a product of humanity paying more attention than asteroid flybys increasing.

 

[Urwumpe]

I consider 1:1250 a pretty good chance for an impact, on Earth, we already freak out for less.

 

[statickid]

"The unlikelyhoods keep piling up greater and greater"

oh no! Watch out! You're treading into the territory of the dreaded gambler's fallacy!

 

[RGClark]

...
For instance the puny, in comparison, asteroid 2012 DA14 would be expected to get so close to the Earth once in 40 years. That such a large comet would get so close to Mars must be much rarer than this. So the chance is less than 1 in 40 in a year. Say it happens for either of two planets; that's a chance of less than 1 in 20 in a year. Say then it happens within a 2 year period; that's 1 chance in 10.
Now the chance of the three encounters occurring within such a close time span is greater than one in several billion. The unlikelihoods begin piling up greater and greater.
...

Another recent comet came unusually close to the Earth in 2010:

Comet and Earth to Have Rare Close Encounter.
by Joe Rao, SPACE.com Skywatching Columnist Date: 01 October 2010 Time: 08:41 AM ET

Rare close encounter
This fall, Comet Hartley 2 will again be passing through the inner solar system, reaching its closest point to the sun (called perihelion) on Oct. 28 at a distance of 98.4 million miles (158.4 million km).
And while en route to the sun, it will also make a very close approach to the Earth. In fact, at 3 p.m. ET on Oct. 20, the comet will be at its closest point to our planet at a distance of 11.2 million miles (18 million km).
It's quite unusual for any comet to approach this close to Earth. Such an event only happens on average perhaps three or four times a century.
http://www.space.com/9240-comet-earth-rare-close-encounter.html

So in a year the chance of a comet getting this close is between 1 in 33 to 1 in 25. Then over a 3 year period about 1 chance in 10. Now the chance of all these rare events occurring within the same short time frame is in the range of tens of billions to one.

Additionally we have the unusual comet coming up in November this year, Comet ISON, expected to be one of the brightest in history:

The 9 Most Brilliant Comets Ever Seen.
by Joe Rao, SPACE.com Skywatching Columnist Date: 05 October 2012 Time: 12:24 PM ET

Comets that are visible to the naked eye during the daytime are rare, but such cases are not unique. In the last 332 years, it has happened only nine other times. Here is a listing of past comets that have achieved this amazing feat.
http://www.space.com/17918-9-most-brilliant-great-comets.html

Now based on this rarity, the combination of unlikely events happening on such a short time scale raises to an unlikelihood of hundreds of billions to one.

This comet also will get unusually close to Mars at 0.07 AU, 10 million km:

Comet C/2012 S1 (ISON) is on its way to skirt around the Sun in November 2013. Will Comet ISON achieve Great Comet status? I summarize what we know about this promising comet and what it might become.
Earth and Mars Close Approaches

Comet ISON makes two interesting close approaches. The first, in October 2013, we will watch the comet pass by Mars at the small distance of only 0.07 AU. This distance is small on the grand scale of the Solar System, but it is still 10 million kilometers. The close encounter may make comet ISON observable to NASA and ESA's spacecraft orbiting Mars. Maybe we can even hope to see a picture of ISON from NASA's Curiosity rover?
Although there is no possibility of such a close approach between the Earth and comet, the second close approach I want to bring up will be between the comet's orbit and the Earth. In January 2014, the Earth will swing past a part of space that Comet ISON already traveled through, at a small distance of only 0.03 AU. This encounter brings up the possibility of a meteor shower on Earth. Meteor showers from Oort Cloud comets are rare events indeed. Stay tuned while astronomers consider this possibility.
http://www.astro.umd.edu/~msk/blog/articles/comet-ison-jan13

Assuming comets get so close as a small fraction of an AU to Mars as rarely as they do to Earth, then on that basis we would also conclude, aside from the brightness issue, that this comet adds another order of magnitude to the unlikelihood of all the events occurring on such a short time frame. (This consideration does not tack on another factor of ten since this comet is already counted. It just offers another way to draw the same conclusion.)

Note also the unlikelihood is almost certainly actually trillions to one because the case of a comet the size of Comet C/2013 A1 (Siding Spring) getting within just thousands of kilometers of a terrestrial planet has to be extremely rare, much worse than the 40 to 1 I estimated previously.

This comet remember dwarfs the size of the asteroid that wiped out the dinosaurs and would cause an even worse global extinction level event if one of such size were to impact Earth.

Now note that trillions to one odds are such that we would not expect it to happen during the entire age of the Solar System.


Bob Clark

 

[RisingFury]

You seem to have a thing for odds, so let me endolge you:

Take a small rock with a volume of 1 cubic centimeter. That's about 3 grams of material. That rock contains about 10^25 atoms.

The probability that the first atom is in the first slot of the rock is therefore 1 in 10^25.

The probability that the second atom is in second slot and not the first is (10^25) - 1, so the probability of these two atoms taking the first two slots in the rock is therefore

1 in 10^25 * (10^25 - 1) = roughly = 1 in 10^50

Ok. Let's add another atom. The probability of that atom being there is 10^25 - 2, so the total odds are

1 in 10^25 * (10^25 - 1) * (10^25 - 2) = roughly = 1 in 10^75

You can continue doing this calculation for the remaining atoms in the rock and you'll end up with a number so big, you won't even be able to write it in paper. So what's the conclusion here? That rocks in the state that they are in, are impossible?

 

[Screamer7]

Maybe it is just coincidence.
But the real reason so many space objects are discovered is the fact that the observations get so much better.
Maybe in the past there was also a lot of space objects and comets that was not detected, but had close encounters with planets like Mars, Earth or even Venus.

I don't think the odds are not that great if you consider the fact that there is a lot of space debris floating around.

 

[garyw]

Note also the unlikelihood is almost certainly actually trillions to one because the case of a comet the size of Comet C/2013 A1 (Siding Spring) getting within just thousands of kilometers of a terrestrial planet has to be extremely rare, much worse than the 40 to 1 I estimated previously.

This comet remember dwarfs the size of the asteroid that wiped out the dinosaurs and would cause an even worse global extinction level event if one of such size were to impact Earth.

Now note that trillions to one odds are such that we would not expect it to happen during the entire age of the Solar System.

Shoemaker-levy 9?

 

[Quick_Nick]

Hehe, pretty relevent on odds:
http://www.facebook.com/photo.php?f...04376056.98921.367116489976035&type=1&theater

 

[RGClark]

Here are some suggested physical phenomena that could cause periodic cometary impacts that were proposed to explain the periodic extinctions that have been observed in Earth's fossil record:

Extinction event.
Patterns in frequency
http://en.wikipedia.org/wiki/Extinction_event#Patterns_in_frequency

It is notable that one of them suggests such an increase in comets should be occurring geologically "soon":

CAMBRIDGE CONFERENCE DIGEST, 02/02/98
http://abob.libs.uga.edu/bobk/ccc/cc020298.html

Another perhaps more benign explanation is a theory proposed in 2007 there should be an increase in the number of sun grazing comets the next few years:

Kreutz Sungrazers
"Several members of the Kreutz family have become Great Comets, occasionally visible near the Sun in the daytime sky. The most recent of these was Comet Ikeya–Seki in 1965, which may have been one of the brightest comets in the last millennium.[1] It has been suggested that another cluster of bright Kreutz system comets may begin to arrive in the inner Solar System in the next few years to decades.[2]"
[ame="http://en.wikipedia.org/wiki/Kreutz_Sungrazers"]Kreutz Sungrazers - Wikipedia, the free encyclopedia[/ame]

This appears to have been validated:

"Suicide" Comet Storm Hits Sun—Bigger Sun-Kisser Coming?
Andrew Fazekas
for National Geographic News
Published January 17, 2011

A recent storm of small comets that pelted the sun could herald the coming a much bigger icy visitor, astronomers say.
Since its launch in 1995, NASA's Solar and Heliospheric Observatory, or SOHO, orbiter has captured pictures of 2,000 comets as they've flown past the sun.
Most of these comets are so-called sungrazers, relatively tiny comets whose orbits bring them so near the sun that they are often vaporized within hours of discovery.
The sun-watching telescope usually picks up one sungrazer every few days. But between December 13 and 22, SOHO saw more than two dozen sungrazers appear and disintegrate.
Seeing "25 comets in just ten days, that's unprecedented," Karl Battams, of the United States Naval Research Laboratory in Washington, D.C., said in a statement. "It was crazy!"
According to Battams and colleagues, the comet swarm could be forerunner fragments from a much larger parent comet that may be headed along a similar path. And such a large icy body coming so near the sun would result in a spectacular sky show.

http://news.nationalgeographic.com/...storm-sun-soho-nasa-sungrazing-science-space/

It's interesting this prediction of the SOHO scientists appears to be confirmed by the discovery of the sungrazing Comet ISON in September, 2012, expected to be one of the brightest comets in history.

In any case an increase of sun grazers could also correspond to an increase in close flybys of comets by the terrestrial planets. A problem though is this increase could itself be due to a disruption of the comets in the Oort Cloud.


Bob Clark

 

[Urwumpe]

Ah yes, the "We have detected patterns in extinctions" theory... or better: Claim.

Claim because it isn't based on the actual data, but rather on wishful thinking. If you have just about one dozen extinction events, a standard deviation of about 30 million years is statistically no problem and proves the claim, right?

(It is way more interesting that the plot has similarities to stock exchange index numbers over time)

Also this annoying misunderstanding of statistics, that many people here already tried to correct in you: We are not overdue for ANYTHING.

Roll a dice. There is always a 1/6 chance for you rolling a 1. So, the stupid person thinks: I had a 1 five rolls ago, so the next one must be a 1. It isn't a 1. Now he thinks he is overdue for a 1. But that is still wrong. He could now roll for days, weeks, even years, without ever seeing a 1 again. It is unluckily to happen, but it has a non-zero chance. Every roll has the same 1/6 chance that a 1 is rolled. Regardless how many rolls without a 1 you had.

The same applies to volcanic erutions (Example of the error: "this volcano erupted about every 750,000 years, so we are now overdue for the next eruption"), meteor impacts, supertsunamis, Moai stampedes and the non-zero chance that all atoms of the underwear of your wife suddenly move 1 meter to the right.

 

[RGClark]

The gambler's fallacy is that if there is a string of events of one result then the next event must be the reverse "to even things out". That is not the case if the events really are independent.
But you can still multiply those chances together to get the chance of them all occurring together assuming they are independent. For example, you can calculate the chance with a fair dice of getting sixteen consecutive 7's as 1 chance in 6^16, which is 1 in several trillion. Still even if there were fifteen consecutive rolls of sevens, if the dice is fair the chance of getting some number other than 7 is not increased on the next roll.
In reality though if you did observe that string of dice rolls that had trillions to one odds against it, you'd assume the dice was loaded. That assuming the dice is loaded means you are looking for a physical explanation.


Bob Clark

 

[Urwumpe]

Still, the chance of having an eight dice is still the same as for all the other rolls. Regardless how unlikely and rare it is to have 90 dice in a row - it can happen. And it can happen to you. And it might even happen even if you switch dices to prevent a slight inbalance (not the intentional loading... many extremely decorated dices are badly balanced).

I remember how one player had been unable to hit anything, despite having to roll just a 4+ with 2D6 (two six-sided dices added together). The chance to hit this is 11/12. And he still failed, rolling snake eyes and threes in a long chain, switching dices, cursing. On another match, he was hitting anything that was in sight. Chance works that way.

The application in such "We are overdue situations": There is no contract between us and the event. We have no prediction. Just a chance. A volcano could have stopped erupting completely. Or the last eruption was so massive, that it changed the eruption pattern completely. We don't know it.

 

[Screamer7]

I did some research on this comet.
It looks like Venus and Mercury are also in for a close flyby by this comet as it hurtled inwards towards the Sun. Especially the Mercury flyby is a close encounter.
What bothered me the most is that comet is discovered so late.
It was discovered in January 2013.
For an object so large, it should have discovered sooner, IMHO.
Imagine the hysteria if a object due to an close encounter with Earth was discovered only a few months in advance!

 

[garyw]

Comets are dark until they develop a coma so very hard to detect, also detection generally involves watching for apparent motion across the sky. Depending on the location of the comet, the apparent motion and a few other things they can be very hard to see.

 

[Screamer7]

Comets are dark until they develop a coma so very hard to detect, also detection generally involves watching for apparent motion across the sky. Depending on the location of the comet, the apparent motion and a few other things they can be very hard to see.

Thanks Gary, I never thought about that fact.