By news editor, on 11 September 2013
In February 2013 an entirely undetected asteroid entered the Earth’s atmosphere above Chelyabinsk, Russia at roughly 60 times the speed of sound and at a very shallow entry angle. The object, which was ‘only’ 17-20 metres across, exploded as it entered the atmosphere producing a bright flash, many small meteorites and a powerful shock wave damaging 7,200 buildings and injuring 1,500 people.
The light produced was brighter than the Sun, the heat from the fireball was felt by people on the ground and it released 20-30 times more energy than the atomic bomb detonated at Hiroshima. It also caused significant panic as the lack of detection meant no warning and no explanation!
So what if something 500 metres across was to come our way? Have you ever wondered if there were secret international committees discussing this?
The NEOShield project is being presented by Davide Perna from LESIA, Observatoire de Paris, at the 2013 European Planetary Science Congress (EPSC) 2013 at UCL this week. His work is analysing the realistic options for preventing the collision of a Near Earth Object (NEO) with the Earth.
The project is funded by the European Commission and as well as the European team that Perna works with, the project includes partners from the established space-faring nations outside of the EU as a realistic response would need a truly international agreement – no good deflecting the asteroid from Paris if it will then hit Nairobi.
The NEOShield project was commissioned in January 2012 with a budget of 5.8 million euros. The work is carried out by 11 institutes, including academics and space companies across six countries. Their work includes laboratory experiments and computer modelling of an NEO’s behaviour should we be forced to interfere with its orbit.
According to Perna, an actual demonstration mission is not feasible in the time or budget of the project, but the hope is that they will have a plan for a demo mission ready if governments are interested.
So what are our options? Perna explained in his talk at the EPSC that we would have three potential plans – a kinetic impactor would bump into the object; a gravity tractor could pull the object away from its earth-bound course without making contact; and finally, the mechanism used in all the films, the nuclear blast deflector.
It is becoming clearer through the work at NEOShield that a reconnaissance mission would be almost essential before deciding which strategy to take. This is because the outcome of any action would depend on the characteristics of the object – its size, water content, structure or porosity. For instance, a very porous object, like a sponge, may simply absorb the energy from a blast by collapsing its air pockets and not breaking up.
Furthermore, each scenario has its own problems. The gravity tractor may simply alter where the object hits the Earth, and with a limited level of accuracy – there won’t be a test run! And although it seems the nuclear blast scenario would be ideal for all cases – destroy the object and it can’t hit the Earth – the fragments it could produce may still hit us. Large fragments of a large object would hardly be less dangerous, and in a scenario where it is obliterated, a huge amount of dust in the atmosphere would also be a problem. As Perna explained: “We must also define the ‘successful outcome’ for the mission.”
So what do they suggest? Currently NEOShield are saying we need tens of years of warning for objects several hundred metres across. Furthermore, they are assuming that in this situation, money would be no object.
An immediate reconnaissance mission would be launched with state-of-the-art instruments aboard to get as much information about the target as possible. This would include cameras, a heat map, an X-ray to detect the density patterns within the structure and Radar Tomography to visualise the layout of the surface. At this point, the theory and models to be built over the next few years of this project would use such information to give our weary world-leader everything needed to take action.
And in the scenario where the object is more than a kilometre across, or where we are given less than two year’s warning? A nuclear blast becomes the only hope – cross your fingers and call Bruce Willis.