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Histogram of close approach distances

L. Elenin

L. Elenin

The histogram shows the distribution of close approach distances to Mars, based on recent calculations. The column width is equal to the radius of Mars. “Red zone” – collision with planet, orange – the number of virtual particles into the Roche limit, which was calculated for comets.

Probability of collision with Mars – 0.08%

L. Elenin

L. Elenin

Initially the calculation was based on the recent observations known for me, including observations by ISON-NM observatory (Feb. 27), Martin Mašek (Feb. 27) and Tomas Vorobjov (March 1). Estimation was made on a sample of 1,000 virtual particles (clones), calculated by the Monte-Carlo method and based on the nominal orbit solution. Calculation shown what only 2 of 1,000 clones will collide with Mars, i.e. 0.2%.

Late at night, we received information what found two another archival observations (October 4, 2012) by Pan-STARRS. Now, arc of observations increased to 148 days! Based on the new data, calculations was restarted again. The collision probability decreased in 2.5 times. Neither clone from a sample of 1,000 virtual particles not collided with Mars. Final calculation is based on a sample of 10,000 clones! It shown that only 8 virtual objects will be collide with the Red Planet, i.e. probability of this event fell from 0.2% to 0.08%, but still high enough for the events of such scale. Minimal distance of close approach, according nominal orbit solution is 0.00039 AU or ~58,000 km.

Close approach to Mars. Up-to-date analysis

After adding the recent measurements, taken by Tomas Vorobjov at Kitt Peak Observatory (March 1, 2013), the distance of closest approach increased to 0.00047 AU (70 500 km). CA time is October 19, 2014, 19:09:24.48 UT. I think what we can fairly accurately estimate these parameters, before the temporary pause in the observations of this comet, due to it’s low elongation. Thanks to Tomas!

If anyone have recent measurements of this comet, I will appreciate if you will send it to me. TIA!

New data concerning the close approach of comet C/2013 A1 to Mars

Chris Smith / NASA

As I wrote previously, the recently discovered comet C/2013 A1 (Siding Spring) will make a extremal close approach to Mars on 19 October 2014. A collision scenario isn’t ruled out either. Today, at the ISON-NM observatory, new astrometric measurements were received for this comet. Based on the existing measurements, more accurate orbital elements were calculated. The results of the second calculation for the close approach show that the comet might pass just 41,000 km (0.000276 a.u.) from the planet’s centre, that is less than 37,000 km from its surface!

Considering the size of the coma, which should exceed 100,000 km near the perihelion of its orbit, it can be said with 100% certainty that the planet will pass through the gaseous envelope of the comet C/2013 A1. Having a very tenuous atmosphere, the surface of the red planet will be subject to intensive bombardments by microparticles which, among other things, might cause malfunction of the space probes currently there.

Observations continue, and will be stopped only in late spring due to small elongation of the comet. In the second half of summer observations will be resumed and we will continue to specify the parametres of the close approach of the comet C/2013 A1 (Siding Spring) and Mars.

Special thanks to Maksim Kakitsev for translation.

Comet C/2013 A1 (Siding Spring) – a possible collision with Mars

L. Elenin

There is a chance that the comet C/2013 A1 (Siding Spring), discovered in the beginning of 2013, might collide with Mars. At the moment, based on the observation arc of 74 days, the nominal close approach distance between the red planet and the comet might be as little as 0.00073 AU, that is approximately 109,200 km! Distance to Mars’ natural satellite Deimos will be smaller by 6000 km, making it 103,000 km. On the 19th October 2014, the comet might reach apparent magnitude of -8…-8.5, as seen from Mars! Perhaps it will be possible to accuire high-resolution images from the Mars Reconnaissance Orbiter (MRO).

Since C/2013 A1 is a hyperbolic comet and moves in a retrograde orbit, its velocity with respect to the planet will be very high, approximately 56 km/s. With the current estimate of the absolute magnitude of the nucleus M2 = 10.3, which might indicate the diameter from 10 to 50 km, the energy of impact might reach the equivalent of staggering 2×10¹º megatonnes! This kind of event can leave a crater 500 km across and 2 km deep. Such an event would overshadow even the famous bombardment of Jupiter by the disintegrated comet Shoemaker–Levy 9 in July 1994, which by some estimates was originally 15 km in diameter.

All that is said above is based on the current measurements, and will of course be refined as more data comes in. In any case, even now we can say that the close approach will happen. The current orbit uncertainty allows for a collision scenario, but the possibility of this is small. Astronomers keep watching this interesting comet, and I will keep you up to date with the news.

Nominal orbital elements were taken from JPL NASA website, calculations were done in Mercury package.

Translated by Maksim Kakitsev.

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