Asteroid hunters and astronomers have recently discovered a comet, named C/2013 A1 (Siding Spring), which is expected to whizz past Mars in October 2014.
According to calculations by the Catalina Sky Survey based at the University of Arizona, it could miss the Red Planet by a mere 100,000 kilometres, Slate.com reports. On the intergalactic scale, 100,000 kms is a very close shave.
More recent calculations by other astronomers predict an even closer encounter, as close as 37,000 km to the surface of the Red Planet. In comparison, all geostationary satellites orbit Earth at an altitude of 35,786km.
Given the short distance, Mars could even pass right through the cloud of gas and material – or coma – around the core, or nucleus, of the comet which is thought to be several hundred kilometres across. As a result, Mars would be bombarded by debris from the coma of C/2013 A1 (Siding Spring), creating heavy meteor showers.
Phil Plait, who runs the Bad Astronomy blog on Slate.com, writes that comets’ orbits are slightly irregular, due to gas jets coming out of the icy nucleus, when ice heats up near stars and sublimates. These jets can modify the trajectory of the spatial body the same way rockets are used in space flights.
He notes that “we won’t know [the orbit] for sure until at least late summer 2013, when more observations are possible” as the comet is “about to get too close to the Sun from our viewpoint here on Earth to observe”.
Brace for a billion megaton impact
It is possible, albeit highly unlikely, that the orbit of the nucleus may be changed enough for it to cross Mars’ path and hit the planet. The consequences would be dramatic: the nucleus is estimated to be between 15km to 50km wide, and impact with the Red Planet could reach a speed of about 55km/s (more than 193,000 km per hour).
According to Plait, in the unlikely event of an impact: “Doing a rough calculation, I get an explosive yield of roughly one billion megatons: That’s one million billion tons of TNT exploding. Or, if you prefer, an explosion about 25 million times larger than the largest nuclear weapon ever tested on Earth. (…) The crater left behind would be hundreds of kilometres across, and be the largest impact Mars has seen in a long, long time.”
All human robotic probes on the surface of the planet will almost certainly be lost by the impact itself or the debris it would eject. “Even a near miss may prove dangerous for the probes,” Plait writes, because of the meteor showers.
It could be an intergalactic firework show that is out of this world.