Scientists who hunt down asteroids and comets that pose an impact threat to Earth should focus on even smaller space rocks and add a British telescope facility in the Southern Hemisphere, according to a report released Monday.

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NASA search programs currently focus on finding asteroids more than 1 kilometer (0.62 mile or 1,091 yards) in diameter, but the British government report recommends giving priority to finding near-Earth asteroids (NEA) as small as 300 yards (275 meters) in diameter.

The report, which describes the devastating effects of an asteroid or comet impact with Earth and the inadequacy of current international efforts to detect them, also made the following points:

• Impacts by asteroids and comets present a real and significant risk to humans and other life on Earth.
• Means now exist to avoid or reduce the fatalities caused by such impacts but only if the threatening objects are detected well in advance of the collision.
• Earth-based telescope systems can carry out most of the necessary detection and follow-up work but they will need to be larger than those of current NEA-detection systems.

These are the main conclusions of a report released today by the British Government. The report describes the devastating effects of an asteroid or comet impact with Earth and the inadequacy of current international efforts to detect these deadly objects.

The report was prepared by three eminent British scientists and was released on the internet by Science Minister Lord Sainsbury.

The task force reviewed the latest information about the impact risk and met with scientists from the United States and Europe. The potential death toll from an impact is much higher than any known artificial or natural disaster. For example an asteroid 1 mile (1.6 kilometers) across could explode with the force of more than 25,000 H-bombs. It would blanket the Earth in a dark dust cloud for months and cause freezing conditions and crop failures. One-quarter of the human population could die in the resulting global famine.

Astronomer Duncan Steel commented on the report, saying that by the safety guidelines normally used for hazardous industries, a massive asteroid impact is "super-intolerable -- the government must act."

Similarly, Alain Maury, a French astronomer who works at an observatory in Chile, told SPACE.com: "We have learned that sometimes, rarely, Mother Nature behaves like a terrorist, dropping 400-megaton bombs on us, and clearly we need to know her intentions for the coming century. In France today, nobody dares to think that looking for asteroids is useful. Reminds me of a time when nobody in the same country cared for Quebec or Louisiana."

Current search efforts are dominated by the U.S. This effort will be boosted in October by the new Japan Spaceguard 40-inch (1-meter) telescope at Bisei. However, the Japanese contribution is unlikely to be enough to reach the 2009 target.