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.
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.
On 12 October 2012, 5:30 UTC, an asteroid 2012 TC4 (which I discussed earlier) made a close approach at 95 000 km from Earth. Its photometric observations were conducted at out observatory 24 hours before the closest approach. During the observations, the asteroid got closer to our planet from 583 400 to 508 600 kilometers. Accuired data allowed to estimate its rotational period, which is 12.2 minutes. More detailed data, as well as the magnitude graph, will be published in the Minor Planet Bulletin. Fast rotation of such small cosmic bodies that come close to Earth is common, and serves as proof of their origin from collisions. I should note that the period of 12.2 minutes isn’t the shortest among asteroids observed at ISON-NM observatory. For example, rotation period of another asteroid – 2012 KP24 is just 2.5 minutes! Absolute record at the moment belongs to the asteroid 2010 TD54, it makes a full rotation in just 42 seconds!
The analysis of evolution of the orbit of asteroid 2012 TC4 during its close approach to Earth shows that its orbit was affected by the gravitational influence of the Earth-Moon system. In the XY plane (in this case the ecliptic plane), the asteroid’s orbit was deflected by ~13 degrees from its original direction. The orbital period of 2012 TC4 around the Sun increased by 20%, from 1.45 to 1.74 years. The graph below shows this. The next close approach of this asteroid with Earth will happen in 5 years.
Translation by Maksim Kakitsev.