Number of Near-Earth Asteroids Lower Than Expected

According to a comprehensive series of observations published by the team managing the Wide-field Infrared Survey Explorer (WISE) spacecraft, it would appear that the number of near-Earth asteroids coming within less than 200 million kilometers (124 million miles) of Earth's orbit was overstated.

WISE – a NASA mission – was uniquely equipped to conduct such investigations, since it carried four of the most advanced infrared sensors ever built. While it was able to find many previously-unknown objects, the satellite also learned that the total number is still a lot lower than expected.

It established that fewer than 20,000 near-Earth asteroids exist in a very specific range. Experts were particularly interested in objects between 100 meters and 1 kilometer (328 feet to 0.62 miles) in diameter. This class of asteroids would have the worst effects, were they to hit us.

Previously, scientists hypothesized that as many as 35,000 such objects may exist, but the new studies cut down these numbers by a wide margin. One of these space rocks is credited with killing off the dinosaurs, nearly 65.5 million years ago, ScienceNOW reports.