NASA report: 4,700 asteroids pose impact hazard to Earth

Posted on May 18, 2012


About 4,700 asteroids of 100 meters diameter and larger represent significant threat to

Asteroid (4179) Toutatis

Earth in case of orbit intersection, a recent NASA report suggests. And only 30 per cent of them have been located so far, while the rest remain under the radar.

­Potentially hazardous asteroids (PHAs) are those massive enough to pass through Earth’s atmosphere without burning to dust and smash to the ground, causing widespread damage.

Intersection of a PHA’s orbit with Earth’s could potentially lead to a destructive collision, the scale of which depends solely on the size of space rock and its composition (considering that we rule out the possibility of Armageddon movie-style Earth-saving scenario).

Detection of such PHAs and estimates of the treat they pose is one of the main parts of NASA’s WISE mission.

The orbits of almost 5,000 PHAs (give or take 1,500) were discovered to lie within a relatively small 8-billion-kilometer range from our planet. Using the infrared light spectrum, the WISE space telescope was able to detect both light and dark objects, estimate the objects’ real size and make predictions about their structure.

The new estimate is much more credible than NASA’s previous rough results. However, so far only about 30 per cent of PHA objects have been discovered. The rest exist only on paper, though their possible orbits have been calculated.


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