The potential threat from near-Earth asteroids can sometimes seem purely theoretical, an academic exercise in how orbits are calculated and refined. But when we start quantifying possible damage from an asteroid strike, the issue becomes a little more vivid. Modeling potential impact points all over the planet, a University of Southampton (UK) team has worked out some stark numbers. The University’s Nick Bailey presented the results at the recent Planetary Defense Conference in Washington.

The researchers put a software package called NEOimpactor to work on asteroids under one kilometer in diameter and assumed an impact speed of 20 kilometers per second. Obviously, larger objects are out there and the impact velocity is arbitary, but asteroids in this size range seem to hit the Earth every 10,000 years, frequent enough that the next one that does hit will probably fit this description. Says Bailey:

‘The consequences for human populations and infrastructure as a result of an impact are enormous. 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.’

Indeed, while a 100 meter asteroid could cause relatively localized damage across several countries, doubling the object to 200 meters causes tsunamis on a global scale, assuming an oceanic hit. In terms of casualties, the study sees China, Indonesia, India, Japan and the US as the most vulnerable, though obviously a direct hit on any heavily populated area would be catastrophic.

Asteroid infrastructure damage

Economically speaking, where the infrastructure is tells much of the tale. Put dense development along the coastlines of economically prosperous areas and you open yourself to the threat of tsunamis and earthquakes emmanating from a wide variety of impact areas. Sweden’s long coastline thus places it in high danger economically, while an impact in the north Atlantic could send devastating tsunamis into both Europe and America. Severe economic effects would clearly result from a strike involving China or Japan.

Image: The areas of maximum infrastructure vulnerability following an asteroid impact. Credit: Nick Bailey/University of Southampton.

Although we’re currently engaged through projects like the Spaceguard survey in cataloguing NEOs larger than one kilometer in diameter, the smaller objects represented in the Southampton study are largely undetected. The risk of being blindsided by such an object emphasizes our need to develop a space-based observation platform for tracking asteroids of this size, along with providing more accurate information about the movements of larger Earth crossers. Bailey again: “The threat of the Earth being hit by an asteroid is increasingly being accepted as the single greatest natural disaster hazard faced by humanity.”