Friday, September 30, 2011

Good news: Astronomers find there are far fewer killer asteroids than we feared Bad news: There are still a million we haven't seen - 30th Sept 2011

That's a relief - there are many fewer 'mid-sized' Asteroids near Earth than was previously thought. There are roughly 19,500 -- not 35,000.

But while the risk of impact is smaller, according to NASA, the majority of them remain to be found.

Mid-sized, by the way, isn't small - it refers to asteroids in a size range between 330 and 3,300 feet wide, which could destroy a city-sized area were they to hit Earth.

NASA's latest scan used the Wide-field Infrared Survey Explorer, or WISE and took two infrared scans of the entire celestial sky, scanning the entire sky twice in a series of infrared photos between January 2010 and February 2011. The scan aimed to find asteroids 'near Earth' - ie within 120 million miles.

NASA's scientists were cautious about the result, saying only that the risk to Earth could be 'somewhat less' than previously thought. Scientists also admit there could be 'up to a million' smaller asteroids that have not yet been detected - which could 'cause damage' if they hit Earth.

What is definitely good news is that the likelihood of a 'planet-killer' - the mountain-sized asteroids in the 'large-sized' range, above 3,300ft - appears to have fallen more significantly.

There are only 981 of these objects near Earth according to the latest estimates, and NASA has found 911 of them. Read More