NASA should extend its search for near-Earth objects to smaller asteroids, a team of experts has warned. The panel compared the added cost of tracking smaller asteroids with the benefits of knowing what risk they pose, and concludes that it "justifies substantial investment".
Since 1998, NASA has been tracking asteroids larger than a kilometre across that come within 45 million kilometres of Earth's orbit. These big rocks are the easiest to find, and the programme is on track to meet its 2008 goal of finding 90 per cent of the 1000 or so such objects thought to exist. Yet while such an asteroid could cause global devastation, an impact is extremely unlikely.
In contrast, half a million or so objects larger than 50 to 100 metres across come within seven million kilometres of the planet. A strike is likely roughly once every millennium, causing regional devastation. The panel compared the ...
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