Talk:C/2013 A1 (Siding Spring)

Chance of impact

A back-of-the-envelope calculation suggests there's currently about a 1:73k chance of the comet hitting Mars.
—WWoods (talk) 18:40, 28 February 2013 (UTC)

The best estimate I have seen suggests roughly a 1 in 7075 chance. -- Kheider (talk) 00:00, 1 March 2013 (UTC)

mAU

Do we really want to use mAU in the table? I am concerned that the average reader will just be further confused by it. -- Kheider (talk) 11:49, 1 March 2013 (UTC)

Point. But I don't like AU in this context; it's the wrong scale unit, so you have to count the zeros to see the difference between 0.007 and 0.0007. What about converting to Mm?

—WWoods (talk) 19:30, 1 March 2013 (UTC)

For now I have gone back to using standard AUs to better match the JPL Database source and to hopefully prevent confusion for casual readers. Hopefully adding in the spaces "&nbsp ;" will help align the columns better. -- Kheider (talk) 20:43, 1 March 2013 (UTC)

Eccentricity

JPL Horizons heliocentric eccentricity before and after Mars perturbation

Observation arc (in days)	Nominal distance (AU)	Nominal passage time (UT)	Epoch 19 Oct 2014 eccentricity	Epoch 20 Oct 2014 eccentricity	Epoch 2050 Barycentric Orbital period
74	0.00070	21:00	1.0005	1.001
148	0.00035	19:28	1.0008	0.99974
154	0.00073	18:50	1.0008	1.00038
162	0.00079	18:45	1.0009	1.00044
171	0.00080	18:44	1.0009	1.00044	424,000
185	0.00076	18:51	1.0009	1.00041	358,000
201	0.00080	18:45	1.0009	1.00045	432,000
211	0.00079	18:45	1.0009	1.00044	418,000
244	0.00082	18:41	1.0009	1.00046	478,000
293	0.00082	18:41	1.0009	1.00046	482,000
341	0.00089	18:32	1.0009	1.00051	725,000
360	0.00089	18:32	1.0009	1.00051	736,000
428	0.00096	18:25	1.0009	1.00056	1,195,000
465	0.00092	18:28	1.0009	1.00054	906,000
612	0.00088	18:32	1.0009	1.00049	621,000
662	0.00088	18:33	1.0009	1.00048	565,000
694	0.00093	18:28	1.0009	1.00050	737,000
733	0.00093	18:28	1.0009	1.00051	1,200,000

With an observation arc of 74 days, the nominal comet makes a backside pass of Mars (21:00), increasing orbital energy. With an arc of 148 days, the nominal comet makes a front-side pass of Mars (19:28), decreasing orbital energy. Looking at Aldo Vitagliano's magenta impactor, impact scenarios seem to occur around 20:00 to 20:30. -- Kheider (talk) 18:00, 3 March 2013 (UTC)

Inbound the comet had an orbital period of millions of years (Barycentric Epoch 1950 = 11 million years). -- Kheider (talk) 13:44, 17 January 2014 (UTC)

Date

I believe the first line in that section should read: "The comet will pass extremely close to Mars on or around 19 October 2014". Not the current, "The comet will pass extremely close to Mars on 19 October 2014." Does anyone agree with me? – AJL^talk 07:23, 6 March 2013 (UTC)

The closest approach will occur at 2014-Oct-19 19:28 (± 01 hr 03 min). Even the 44 day observation arc had a closet approach of 2014-Oct-19 10:26 (± 10 hr 05min). The orbit is well determined. What is not determined is whether it will impact Mars since Mars is inside the 310,000km uncertainty region. -- Kheider (talk) 10:49, 6 March 2013 (UTC)

Fair enough. I hadn't read the reference attached to that statement before posting. Thanks for the pleasant reply. :) – AJL^talk 01:18, 14 March 2013 (UTC)

impact

Is all of the discussion about the impact results needed, since now an impact is essentially ruled out? Bubba73 ^{You talkin' to me?} 02:54, 16 April 2013 (UTC)

I see only two sentences discussing impact results ("The resulting upper limit energy of impact could reach 20 billion megatons.", "The diameter of an impact crater would be roughly ten times the diameter of the comet's nucleus.") plus the table, which seem reasonable to keep IMO, since much of the notability of the comet came from the potential impact. --Roentgenium111 (talk) 12:55, 16 April 2013 (UTC)

sortable table

There is no need for the first table to be sortable. It is already in order by the only thing that matters - the length of the observation arc. There is no need for the reader to sort it on any of the other columns. Bubba73 ^{You talkin' to me?} 14:59, 16 April 2013 (UTC)

Someone might want to sort it by nominal passage time. -- Kheider (talk) 17:42, 16 April 2013 (UTC)

million Mt

Table titled "Comet impact at 56 km/s into sedimentary rock" - please, use Megatons, Gigatons (preferably with scientific number notation or teratons/petatons) of TNT for Kinetic energy. 100 million Mega Tons (cause I guess that's what "100 million Mt" is suppose to mean) is very confusing making recalculations and comparisons more difficult than needed. SkywalkerPL (talk) 10:30, 18 November 2013 (UTC)

Mt stands for Megatons. I believe using a single unit makes it easier for the layperson as I find scientific notation often loses the layperson. For better or worse most asteroid impacts are estimated using Mt. -- Kheider (talk) 17:43, 18 November 2013 (UTC)

nucleus vs coma

Since we're talking about 10s of thousands of miles can we get specific about distances with respect to what? I mean the coma of the comet might be tens of thousands of miles wide while the nucleus of the comet might be a mile or less. Using "Comet" for the distances involved is too vague. --Smkolins (talk) 20:18, 9 December 2013 (UTC)

Speculation on Martian Meteor Shower

The article currently states that a "spectacular meteor shower" on Mars is unlikely, reference Emily Lakdawalla's blog from March. Here's a NewScientist article that quotes other experts that aren't so sure. http://www.newscientist.com/article/dn24715-fiercest-meteor-shower-on-record-to-hit-mars-via-comet.html#.UqdOEidQVeE The journal paper in Icarus is already cited as a reference in the article, minus the meteor storm. Geogene (talk) 17:30, 10 December 2013 (UTC)

Comet Siding Spring #

How many "Comet Siding Spring"s are there? Which one is this comet? --JorisvS (talk) 18:47, 28 December 2013 (UTC)

There are 12 comets and 1 asteroid by that name. -- Kheider (talk) 18:59, 28 December 2013 (UTC)

So this one would be like ... Siding Spring 12? --JorisvS (talk) 22:25, 28 December 2013 (UTC)

Odds of impact

Yes, the odds for impact are very low. However, if you want to report the April 2013 odds, why do it in 3 separate entries? Cheers, BatteryIncluded (talk) 18:27, 17 April 2014 (UTC)

All of those estimates are more than a year old. Removing the dates from the estimates makes them appear as if they are still current. Every time the observation arc became longer the odds dropped. There is no longer ANY chance of a direct impact by the comet nucleus. -- Kheider (talk) 19:35, 17 April 2014 (UTC)

Once more: I know there is a negligible chance of impact; I do not contest the data/models, but the format and prominence given. You reverted my edit when I merged 3 separate entries starting with "As of April X the odds of impact are...". As far as I know, this is not a timeline where you can have an argument in favor of outdated chronological estimates. Being that we agree that the odds impact are nil, we must update the article accordingly by giving proper weight (little) to the old estimates. That is what I did; a one-liner is enough; add the dates if you will. Do you still think it is better the way it was before? Why? CHeers, BatteryIncluded (talk) 23:45, 17 April 2014 (UTC)

This edit was bad because it gave the suggestion that the odds of impact from March 2013 were more recent than the odds from April 2013. -- Kheider (talk) 00:06, 18 April 2014 (UTC)

Note that there is a gambling site now taking anonymous bets on the distance at the Mars encounter; see http://bitbet.us/bet/820/comet-2013-a1-will-pass-within-100-000-kilometers/ . It should be expected that people will attempt to change the information on the wiki page in order to influence the betting odds. Because anyone can be a better, there is no one who is free of potential conflict of interest in editing the page. Should it be locked? — Preceding unsigned comment added by 173.228.13.5 (talk) 20:53, 3 May 2014 (UTC)

Archive.ph

• JPL solution #5 with a 58 day observation arc (2013-Feb-11)
• JPL solution #17 with a 244 day observation arc (2013-Jun-08)
• JPL solution #27 with a 394 day observation arc (2013-Nov-02)
• JPL solution #42 with a 502 day observation arc (2014-Feb-20)
• JPL solution #46 with a 516 day observation arc (Davide Farnocchia 2014-Mar-14 cad=0)
• JPL solution #47 with a 612 day observation arc (Davide Farnocchia 2014-Jun-10)
• JPL solution #53 with a 662 day observation arc (Davide Farnocchia 2014-Jul-29)
• JPL solution #56 with a 676 day observation arc (2014-Aug-13)
• JPL solution #58 with a 687 day observation arc (Davide Farnocchia 2014-Aug-25)
• JPL solution #67 with a 694 day observation arc (Davide Farnocchia 2014-Sep-12)
• JPL solution #97 with a 733 day observation arc (Davide Farnocchia 2014-Oct-07)

NASA TV (Thurs, 9 October 2014@2pm/et/usa) - Comet Flyby of Mars - Discussion.

NASA TV (Thurs, 10/09/2014@2pm/et/usa) - Enjoy! :) Drbogdan (talk) 12:17, 7 October 2014 (UTC)

FOLLOWUP - NASA VIDEO REPLAY (56:15/9 October 2014) - Space Experts Discuss "Comet Siding Spring/Mars Flyby - 19 October 2014 - Flyby" - Enjoy! :) Drbogdan (talk) 01:17, 10 October 2014 (UTC)

MER PanCam photos

[1][2][3] So, this is what the comet looks like from the surface of Mars -- 67.70.35.44 (talk) 05:52, 21 October 2014 (UTC)

Removed image

closest approach distances don't match the description in the text:

Closest approach of Comet Siding Spring to Mars - maximum and minimum distances noted

correction: I see, the closest distance to the comet's orbit is separate from closest approach. image put back. the image might be clearer if it had an added line indicating closest approach of the comet's orbit to mars, 100min after the closest approach of the comet body.

Malronius (talk) 15:31, 24 October 2014 (UTC)

NASA-TV/ustream (Friday, 11/07/2014@12pm/et/usa) - C/2013 A1 Flyby of Mars - Telecon.

NASA-TV/ustream (Friday, November 7, 2014@12pm/et/usa) - experts provide initial science observations of comet C/2013 A1 close flyby of Mars on October 19, 2014 and the Martian atmosphere. - Enjoy! :) Drbogdan (talk) 03:12, 6 November 2014 (UTC)

FOLLOWUP - Space Experts Discuss the Effects on the Martian atmosphere of the Comet C/2013 A1 Flyby of Mars on October 19, 2014 - Archived Discussion => Audio (with visuals; 60:21) - Enjoy! :) Drbogdan (talk) 19:41, 7 November 2014 (UTC)

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Apparent magnitude from Mars

In the article is mentioned that As seen from Mars, C/2013 A1 peaked at approximately apparent magnitude −6 with the source being a twitter post from two months before the closest encounter. I really doubt that the comet actually reached that magnitude, as it appears much, much fainter in the Mars rovers photos [4][5][6]. We need a reliable source after the flyby for the apparent magnitude, not a prediction that could be way off reality. C messier (talk) 07:38, 12 March 2023 (UTC)