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Project NEOShield arose from these considerations. In
2011 the European Commission selected an international group
of scientists and engineers under its Seventh Framework Pro-
gramme for Research and Technological Development (2007-
2013) to investigate methods of defence against asteroids. The
primary goal of the resulting project, NEOShield, is to produce
detailed designs of space missions to test the effectiveness of
promising asteroid deflection techniques. A consortium of 13
partners, under the aegis of DLR, is being funded for a period of
three-and-a-half-years from January 2012, supplementing the 4
million euros of European Commission support with 1.8 million
euros of their own resources.
On 15 February 2013, an asteroid 17 metres in size and weighing some 10,000 tons entered Earth’s atmosphere at
around 64,000 kilometres per hour, exploding over Chelyabinsk in Russia. The energy released was equivalent to 500
kilotons of TNT, about 30 times that of the Hiroshima atomic bomb. The resulting blast wave damaged buildings and
caused injuries to around 1200 people through flying debris and glass splinters. On the very same day, asteroid 2012
DA14, 45 metres in diameter, passed only 28,000 kilometres from Earth, beneath the orbits of TV and communications
satellites. Despite the dramatic combination of the two unrelated events, the collision of a large asteroid or comet with
Earth is actually a very rare event. But if such an impact were to occur it could trigger the worst natural catastrophe our
civilisation has ever experienced. It is worth repeating to be absolutely clear: what we are talking about here is a minus-
cule risk, but one linked to potentially devastating consequences. Ignoring this risk is socially, politically and also
economically very dangerous; it is a subject in which global thinking and acting is vital.
NEOShield – international defence against asteroids
By Alan Harris
When things get too
close for comfort
An asteroid approaches Earth. The
NEOShield project is working towards
preventing a potential asteroid impact.
A near-Earth object, or NEO, is an asteroid or comet with
an elliptical orbit around the Sun that comes nearer than 50
million kilometres to Earth’s orbit. By comparison, the Moon
orbits Earth at a distance of around 400,000 kilometres, and
at opposition, Mars is around 60 million kilometres from Earth.
NEOs can endanger Earth. To date, there are nearly 10,000
known NEOs, ranging in size from a few metres up to 40 kilo-
metres in diameter.
An impact of an object with a diameter of just one kilo-
metre could have global effects; the reason is the enormously
high speed – several tens of thousands of kilometres per hour –
at which the object would enter Earth’s atmosphere. Even so, it
is somewhat reassuring that, thanks to a few, mainly US, obser-
vatories constantly scanning the night sky for NEOs, almost
every object of more than one kilometre in diameter is known
and is being tracked. DLR and the European Asteroid Research
Node, EARN, are contributing to cataloguing the asteroid popu-
lation in the Solar System. No large NEO that could threaten our
civilisation in the next 100 years or so has been discovered to
date.
When Siberia shook 100 years ago…
But how dangerous could smaller NEOs be? There are an
estimated one million objects with diameters between 30 and
50 metres, but only a fraction of these have been discovered to
date. An object of this size is thought to be responsible for the
Tunguska event in Siberia in 1908, when more than 80 million
trees over an area of 2000 square kilometres – about twice the
size of Berlin – were snapped and felled like matchsticks. The
devastation was probably caused by an object that entered the
atmosphere at 50,000 kilometres per hour and exploded at an
altitude of five to 10 kilometres with a blast equivalent to 10
megatons of TNT. Another example of the devastating effects
of a small NEO is Barringer Crater in Arizona, also known as
Meteor Crater. The 50,000-year-old crater remains well
Alan Harris and Line Drube, a postdoctoral researcher at the DLR
Institute of Planetary Research, discuss the physics of NEO defence
methods.
Image components: NASA/JHUAPL und NASA
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