NASA said on Thursday it identified upwards of 90 percent of giant near-Earth asteroids, including ones that are as big as the one which was said to have killed the last generation of dinosaurs eons ago. Amy Mainzer of the NASA Jet Propulsion Laboratory said:
“We know now where most of them are and where most of them are going. That really has reduced our risk…Fewer does not mean none…There are still tens of thousands out there that are left to find.”
The fresh census comes from data from NASA’s sky-mapping spacecraft called Wide-field Infrared Survey Explorer, or WISE, that launched in 2009 to seek out near-Earth objects, stars, galaxies and other cosmic targets.
Unlike sky surveys that have come before, WISE has extremely sensitive instruments which can pick out both light and dark objects, allowing it to receive the most accurate count yet of near-Earth asteroids. The spacecraft only takes a small sample of asteroids of different sizes before estimating how great the population would end up being.
For the very largest asteroids – greater than 3,300 feet across – NASA says 911 of the 981 that are said to exist have been found.
Former estimates put the number of medium-sized asteroids at 35,000, however WISE data indicate there are some 19,500 between 330 and 3,300 feet wide. Only about 5,200 were found and scientists said that there still is tons of work left to identify the potentially hazardous ones.
Alas, WISE isn’t yet totally equipped to detect the more than a million smallest asteroids which could cause damage should they impact planet Earth.
By locating the majority of the giant asteroids, NASA has gone ahead and fulfilled a goal that was set by Congress in 1998. More recently however, the space agency was asked to find 90 percent of asteroids which are at least 460 feet in diameter – just a little smaller than the Superdome in New Orleans – come the year 2020.