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  #41  
Old 08-03-2013, 10:48 PM
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Kal (Andrew)
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Fascinating.

Imagine the drama we would be facing if this was coming this close to earth instead of mars.

*goes to watch armageddon*
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  #42  
Old 11-03-2013, 06:22 AM
carl37 (Carl)
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New orbit out from JPL.

Using 183 observations over 154 days, they've revised the nominal approach distance to 0.000736 AU, with a maximum distance of 0.0023 AU.

In lay terms, that's 110,000km and 350,000km respectively. A bit further away than the last estimate.
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  #43  
Old 11-03-2013, 03:48 PM
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TheAstroChannel (Sean)
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Some good news!
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  #44  
Old 11-03-2013, 03:54 PM
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Straight up I'll admit to being probably wrong, so let me know if I am, but, I seem to recall the famous Antarctic meteorite which was ejected from Mars after a collision with whatever it was that collided with Mars to cause said ejection. This meteorite supposedly showed evidence of life on Mars, I'm sure you all know the one I'm referring to. It was apparently estimated that it took some million/s of years from being ejected from Mars to landing in Antarctica. Given the same time span for ejecta from the possible up-coming comet/Mars collision, that out not to be a problem for us.

Or could this be a case of KE on impact being far greater than the impact that led to the meteorite landing in Antarctica, and thus a greatly shortened time span from Mars to Earth.

Stuart
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  #45  
Old 11-03-2013, 06:40 PM
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tonybarry (Tony)
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Hi Stuart,

Think of a game of billiards when the first player breaks the triangle. The balls go everywhere. In the same way, C/2013 A1 impacting Mars would scatter stuff widely.

THe difference between billiards and the comet impact is that space is vast and the ejecta (even though millions of tonnes in weight) is tiny by comparison.

What this would do is increase the risk of impact (by micrometeors) to space vehicles. The obvious question is ... by how much ? but to that I have as yet no answer. Gut feelings say ... considerably increased risk. But guts are notoriously inaccurate calculators.

Regards,
Tony Barry
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  #46  
Old 18-03-2013, 07:28 PM
moozoo (Michael)
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Quote:
Originally Posted by mithrandir View Post
Unfortunately find_orb won't generate an ephemeris with the necessary number of digits of precision to generate the graph. Trying those MPEC numbers in Starry Night it generates closest approach at 2014-10-19 23:21 UTC and 348526 km.
I tried find_orb first as well.

If you import the 183 observations from MPC into Exorb (http://chemistry.unina.it/~alvitagl/solex/) and then load that into Solex and run a close encounters scan, you will end up with almost exactly the same result as is displayed on the jpl site. i.e. 0.0007 au.
You can also use Exorb to generate a large number of Monty Carlo data fits and then run them all though Solex to generate a histogram of close approaches.
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  #47  
Old 19-03-2013, 11:03 AM
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Quote:
Originally Posted by moozoo View Post
I tried find_orb first as well.

If you import the 183 observations from MPC into Exorb (http://chemistry.unina.it/~alvitagl/solex/) and then load that into Solex and run a close encounters scan, you will end up with almost exactly the same result as is displayed on the jpl site. i.e. 0.0007 au.
You can also use Exorb to generate a large number of Monty Carlo data fits and then run them all though Solex to generate a histogram of close approaches.
Do you need the full version of SOLEX or will the Lite version work?

There are now 213 observations in MPEC, and after find_orb discarded 4 outliers, SNP now predicts 64822Km at altitude 65° from a Abalos Undae, Mars (81N, 83W) at 18:37 UTC on 2014-10-19. With a bit of hunting I might find where it will be nearer to the zenith at closest approach.
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  #48  
Old 20-03-2013, 09:52 PM
moozoo (Michael)
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Originally Posted by mithrandir View Post
Do you need the full version of SOLEX or will the Lite version work?
From memory the Lite version will work fine. The full version is postcard ware and includes alot more stars and asteroids.

Solex is a very accurate numerical intergrator, comparable to the jpl one.
The documentation give a large number of graphs showing the errors between solex and jpl's DE421 and DE406 over 10000+ years.

I've attached a histogram generated from 1256 monty carlo generated fits to the observations. I didn't remove any outliers. I have since worked out how in EXORB to find and remove the 4 you mentioned. It didn't make much of a difference to the best fit. So I doubt the histogram will be very different either.

http://moozoo.dyndns.org/misc/MINDIST.jpg
I also posted this at http://cosmoquest.org/forum/showthre...ith-Mars/page5
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  #49  
Old 20-03-2013, 10:38 PM
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Originally Posted by moozoo View Post
From memory the Lite version will work fine. The full version is postcard ware and includes alot more stars and asteroids.
I've tried exorb7 with the MPEC data I have today and I must be doing something wrong because the elements it generates are nothing like what I get out of find_orb with the same data, or the values from MPC or JPL. Maybe we could take this offline.
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  #50  
Old 27-03-2013, 11:34 AM
moozoo (Michael)
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Video of computing comet close approach using exorb and solex http://moozoo.dyndns.org/C2013A1/C2013A1Solex.mp4

Using the Extras option (!) you can increase the order of the intergration and enable the use of 80bit floats. It doesn't make much of a difference.

To use findorb to compute the orbit and then use solex to do the intergration you need to use findorb's "Make Ephemeris"
http://moozoo.dyndns.org/C2013A1/findorb.jpg
Take a copy of the C2013A1.SLX file and edit in the findorb values.
To convert to the units used by solex
Take the 1st number and replace the first line in the .slx file with it
Take the 2nd,3rd and 4th numbers and multiply by 149597870.691/1000000 and replace the 3rd line in the .slx file with it
Take the 5th,6th and 7th numbers and multiply by 149597870.691/(24*60*60) and replace the 4th line in the .slx file with it

The 149597870.691 is the AU_TO_KM constant in the findorb source
The result
--------------
2456205.093440
0 0 0 0.0000000E+00 C2013A1
1.3102997512433800E+02 1.1404778167143200E+03 -2.9852251770828400E+02
3.1353047253305100E+00 -1.4621796132689200E+01 -5.2773661621146100E-01
0.00000000E+00 0.00000000E+00 0.00000000E+00 1.11000000E-01
--------------------------------

Solex using a filtered (residuals over 1.5 removed) findorb orbit gave a close approach of 145614 km at 18:25
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  #51  
Old 27-03-2013, 02:28 PM
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Quote:
Originally Posted by moozoo View Post
Solex using a filtered (residuals over 1.5 removed) findorb orbit gave a close approach of 145614 km at 18:25
With the current 220 (less 4) observations, find_orb predicts 125997 km at 18:39 UTC.

If I set find_orb's std dev filter to 1.5 it eliminates 8 observations and the closest approach increases to 133002 km.

If I follow your steps exactly I get the same values from EXORB/SOLEX. I have all the MPEC K12 and K13 files and while extracting all the K13A010 records should give something identical to the file you get from the DB query it doesn't seem to do so.

Last edited by mithrandir; 27-03-2013 at 04:46 PM.
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  #52  
Old 09-04-2013, 02:16 PM
starchild (Guillaume)
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Originally Posted by mccann73 View Post
If by some remote chance this comet does impact, as well any possible effects on earth, it would be interesting to see the long term effects on Mars, apart from the obvious destruction at the impact zone, wouldn’t the amount of dust and material thrown into the atmosphere have an impact on global temperature (atmosphere and land), depending on the location would the impact zone melt large amounts of permafrost, increasing the atmospheric pressure, possibly even enough for running water?


Cheers
Andrew
I agree with you on that Andrew! I wonder if it would change the global temperature...

Cheers,
guillaume
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  #53  
Old 09-04-2013, 11:43 PM
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mithrandir (Andrew)
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With every additional set of observations from the MPC (now 247 less 4 outliers) a hit seem less likely.

Today's projected close approach is 135741 km.
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  #54  
Old 13-04-2013, 03:21 PM
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tonybarry (Tony)
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Universe Today posts an article on C/2013 A1 - effectively ruling out a cometary impact on Mars.

http://www.universetoday.com/101437/...4/#more-101437

Odds are less than 1 to 1e5 against.

Regards,
Tony Barry

Last edited by tonybarry; 13-04-2013 at 03:21 PM. Reason: typo
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