It may not happen within our lifetime, or even for many centuries to come. But one day, almost inevitably, the human race will face the very real threat of extinction from an extra-terrestrial object from above. The issue of whether or not our governments and international agencies are adequately prepared, and technologically equipped, to avert this potentially cataclysmic event could ultimately decide the fate of humanity.
The prospect of an asteroid hitting Earth and wiping out civilisation has long engaged the imagination of Hollywood film directors. This doomsday scenario is also occupying the minds of researchers at The Open University’s Department of Physical Sciences (DPS) in Milton Keynes.
The team are key partners in the pan-European NEOShield project, which is formulating detailed blueprints for critical space missions that could be initiated should a large asteroid be identified as being on a collision course with Earth.
The project also considers the key inter-governmental decisions that would need to be reached in order to initiate an effective global response to an imminent disaster.
Similar events are not unprecedented. In recent decades, NASA and other space agencies have monitored thousands of near-Earth objects (NEOs) that have passed alongside our planet. The majority that encroach the Earth’s atmosphere are small and disintegrate at high altitudes, with only small fragments ever making impact with the ground. But their size and frequency remain unpredictable.
The probable consequences of a major asteroid impact are chilling. The mass extinction of the dinosaurs has been attributed to an asteroid 10km-15km in diameter which hit Mexico’s Yucatan Peninsula some 65 million years ago. Major strikes have continued to happen right up to the present day.
In June 1908, an asteroid measuring around 30m-50m across exploded in the skies over Tunguska in the largely uninhabited Siberian Plateau, Russia, obliterating 2,000 square kilometres of forest.
Trees were knocked down and burned over hundreds of square kilometres by the Tunguska meteoroid impact. This image is cropped from the original, taken in May 1929 during the Leonid Kulik expedition. The largely uninhabited nature of Siberia meant that trees, rather than people, took the brunt of the impact.
“If an object of that size had struck a densely populated city then the result would have been thousands or even millions of deaths, and major destabilisation of our political and socio-economic systems,” explains Dr Tim Ringrose, Project Officer at The Open University’s Department of Physical Sciences.
The NEOShield project employs a global and multidisciplinary approach to disaster mitigation, drawing on the expertise of several world-leading European research institutes, together with leading US and Russian space research agencies. It is co-ordinated by the German Aerospace Center’s Institute of Planetary Research.
The OU’s Hypervelocity Impact Laboratory, based in the Department of Physical Sciences (DPS) at Milton Keynes, and led by Dr Manish Patel, has been conducting detailed research surrounding one potential mitigation scenario.
This would entail directing a spacecraft into the asteroid, striking it at such velocity that the sheer force of impact would deflect the asteroid out of its orbital path and away from the Earth – effectively averting Armageddon.
Central to DPS’ research is the All-Axis Light Gas Gun, a unique piece of equipment capable of firing small projectiles into a range of materials at immense velocities. The impact is sufficiently devastating to cause many metals to become molten in the instant they are blasted by the tiny steel ball bearings that are unleashed by the Gas Gun at 7 kilometres per second. Slow motion cameras capture the destruction in the blink of an eye.
The Light Gas Gun is one of a handful of its kind in the UK, but the apparatus is unique in that it can be configured to fire vertically as well as horizontally, enabling researchers to study impact forces upon liquids and loose materials as well as solids.
Researchers measure the momentum transfer resulting from impacts into a range of materials that replicate the variously dense, rocky, metallic or icy constituent materials of interstellar asteroids. The data collected is crucial in enabling their German counterparts in the NEOShield initiative to enhance the computer-generated models that simulate the consequences of a spacecraft slamming into an asteroid.
Dr Ringrose, who oversees the operation of the Light Gas Gun, is convinced that a multinational approach to disaster mitigation is essential:
“The aim of our investigations involving the Light Gas Gun is to prove that our concepts for mitigating against an extinction-level event are scientifically sound and technologically viable. The multinational approaches being undertaken through the NEOShield project are significant. Individual governments are understandably reluctant to invest billions in a space programme designed to counter what would only ever be a small and theoretical probability of an incoming asteroid landing within a populated area under their jurisdiction. They would point out that some 70% of the planet is covered by oceans and so, if an imminent impact was identified, an asteroid would be likely to land in an unpopulated region anyway.”
The deployment of a successful mission to deflect or destroy an incoming asteroid would also involve a preliminary reconnaissance mission, whereby a space probe would conduct a detailed analysis of the size and composition of the celestial body prior to a particular mitigation scenario being green-lit by NASA.
The deflection scenario advocated by CEPSAR (the OU’s research centre for physical and environmental sciences) researchers could be effective on asteroids of up to 300m in diameter, sizeable enough to cause an extinction-level event on Earth. However, for larger bodies, alternative mitigation techniques would have to be considered.
Other institutes within the NEOShield consortium are exploring a range of alternative scenarios, from the detonation of a nuclear device on the surface of the asteroid, to exerting a gravitational force on the asteroid in order to divert its course.
Dr Ringrose, though, cautions that governments and international agencies are currently too complacent towards the threat posed from Near Earth Objects (NEOs), stressing: “We would need to plan these missions many years in advance. However, by the time we were able to ascertain the precise landing site of an approaching asteroid, it would already be too late to mobilise a spacecraft to destroy it.”
Prior to the NEOShield initiative, the Light Gas Gun had been engaged in studies investigating the potentially disastorous consequences of interplanetary particles colliding with spacecraft. A similar scenario was recently portrayed in the Oscar-nominated Hollywood blockbuster “Gravity,” which saw Sandra Bullock battling to survive after her spacecraft was torn to shreds by space debris orbiting the Earth.
“At extremely high velocities, even particles as tiny as a grain of sand become deadly projectiles,” explains Dr Ringrose. “An impact with a manned spacecraft could be catastrophic, destroying scientific instruments on board and, worse, causing sudden depressurisation of the spacecraft, killing everyone on board.”
He remains confident that DPS’ research is vital to the successful resolution of the NEOShield project, and could benefit future generations of scientists enormously:
“We can only hope that our civilisation will not be threatened by a near-earth object (NEO) for many generations to come. But carrying out the research groundwork now will leave us better prepared to mobilise a successful space mission when the time comes.”
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