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[Centaur]

Hyperbolic Comet C/2013 A1 (Siding Spring) may be as wide as 50 km. There is a possibility of it crashing into Mars on 2014 OCT 19, according to Russian comet hunter Leonid Elenin in this article: spaceobs.org/en/news/

The comet will approach closest to Earth on 2014 SEP 05. Its maximum brilliance is expected on 2014 SEP 10 and is estimated at magnitude +7.7.

I’ve created a diagram with an “overhead” view of the comet, Mars, Earth and Sun. It’s for the months surrounding the comet’s encounter with Mars. It can be viewed from the bottom of my comets webpage: CurtRenz.com/asteroids.html

[Paulie pchris00]

The comet is going backwards.

And it must have a pretty steep inclination to the ecliptic if closest Earth approach is September 5?

[Centaur]

Feb 26, 2013 21:17:09 GMT -6 Paulie pchris00 said:

The comet is going backwards.

And it must have a pretty steep inclination to the ecliptic if closest Earth approach is September 5?

Indeed, Paulie, that’s an astute observation. Comets are equally likely to come from any direction. The 129° inclination posted on my chart is equivalent to 51° but retrograde. So the comet is sweeping toward Mars from south of the ecliptic plane, while revolving around the Sun in a direction generally opposed to that of the planets.

[Chicago Astronomer - Astro Joe]

If there is a contact hit, looks like we will miss the event and have to wait until the morning after for groundbased scopes.

[Paulie pchris00]

If there is an impact, it will be awfully tough for ground based telescopes to observe, given our distance from Mars in October 2014, but I bet a handful of dedicated "amateurs" get some images worth seeing, if in fact, there is something to see.

And we have orbiters that can possibly catch any impact up close, and maybe even as it happens. It will be interesting to see how this comet's orbit is refined.

[Chicago Astronomer - Astro Joe]

At an estimated -8 from the Mars perspective, I think Earthscopes could pick it up quite easily. Perhaps not the debris ejecta, but the comet tail pointed at the surface.

Martian doomsday.

[Centaur]

I’ve been in contact with Aldo Vitagliano, the creator of the Solex astronomical numerical integration program. He developed 50,000 clones of the comet that fit within the possible error range of the still quite preliminary data. After running them through Solex he got 6 hits or 0.0012%. So a collision appears extremely unlikely, though still possible. Aldo hopes to know more tomorrow. If so, he’ll send me a file with a thousand clones including a few impactors to input into my copy of Solex. That may cause me to fine tune my chart: www.CurtRenz.com/comets

[Centaur]

Due to the latest (March 1) observational data for comet C/2013 A1 (Siding Spring), today Aldo Vitagliano provided me with initial conditions for 2000 clones to be entered into his Solex numerical integrator. The clones represent deviations from the nominal solution within the range of reasonable error. He has upgraded the probability of collision with Mars to 1 / 333 from his previous figure of 1 / 8333.

In response, I have updated my diagram illustrating an “overhead” (north of ecliptic) view of the encounter with output from what Aldo considers to be the nominal solution. Under the nominal solution during closest approach to Mars the comet’s heliocentric eccentricity switches from hyperbolic to elliptical. The closest approach between the centers of Mars and the comet utilizing the nominal solution is 50,586 km (81,410 mi) on 2014 OCT 19 at 19:21:24 UT. My diagram can be found at: www.CurtRenz.com/comets

[Centaur]

I’ve added an equatorial finder chart. It may give you a better idea regarding the relative movements of Mars and the comet: www.CurtRenz.com/comets