Researchers at the University of Southampton have developed a software package for modelling asteroid impacts that enables them to assess the potential human and economic consequences across the globe.

The software, called NEOimpactor, has been specifically developed for measuring the impact of 'small' asteroids under one kilometre in diameter, and early results indicate that the ten countries most at risk are China, Indonesia, India, Japan, the United States, the Philippines, Italy, the United Kingdom, Brazil and Nigeria.

'The threat of the Earth being hit by an asteroid is increasingly being accepted as the single greatest natural disaster hazard faced by humanity,' comments Nick Bailey of the University of Southampton's School of Engineering Sciences, who developed the software with University colleague Dr Graham Swinerd, and Dr Richard Crowther of the Rutherford Appleton Laboratory .

'Since 1998 the international Spaceguard survey has been cataloguing all near earth asteroids (NEA) larger than one kilometre in diameter. However, small asteroids, under one kilometre in diameter, remain predominantly undetected. While the direct consequences might not be quite as extreme, these small objects exist in far greater numbers and therefore will impact more frequently. It is on these sub-kilometre asteroid impacts that we have been focusing to assess the consequences for both humans and for infrastructure across the globe.'

Initial investigations have examined how the consequences of an impact change with increasing impact energy. Taking a spherical stony asteroid travelling at 12,000 miles per second and varying the diameter to increase kinetic energy, the results indicate that a 100 metre diameter asteroid will predominantly cause localised casualties and damage across a few countries when impacting on either land or ocean. However, the consequences of a 200 metre diameter asteroid hitting the ocean increase significantly, with the generated tsunamis reaching a global scale. At 500 metres in diameter, almost any ocean impact will generate significant casualties and economic cost across the world.

The team used the raw data from the multiple impact simulations to rank each country based on the number of times and how severely they would be affected by each impact. Early results show that in terms of population lost, China, Indonesia, India, Japan and the United States face the greatest overall threat; while the United States, China, Sweden, Canada and Japan face the most severe economic effects due to the infrastructure destroyed.

In both rankings, the United Kingdom appears eighth in the list of countries most affected. Of the top twenty for each ranking, over half the countries appear in both lists.

'The consequences for human populations and infrastructure as a result of an impact are enormous,' continues Nick Bailey. 'Nearly one hundred years ago a remote region near the Tunguska River witnessed the largest asteroid impact event in living memory when a relatively small object (approximately 50 metres in diameter) exploded in mid-air. While it only flattened unpopulated forest, had it exploded over London it could have devastated everything within the M25.

'Our results highlight those countries that face the greatest risk from this most global of natural hazards and thus indicate which nations need to be involved in mitigating the threat.'