Last month's flyby of Earth by asteroid 2012 KT42 was the sixth-closest asteroid encounter on record. It whizzed by inside the orbital distance of Earth geosynchronous satellites.
Asteroid KT42 was discovered by the Catalina Sky Survey project in Tucson, Ariz., which spotted the object a scant 23 hours before its closest approach on May 29.
The object's color signature indicates it has a carbon-rich composition, perhaps analogous to carbonaceous chondrite meteorites found on Earth, from which a moderately dark reflectivity (albedo) is inferred.
By knowing both the reflectivity and visible brightness of the object, the deduced size of asteroid KT42 is about 7 meters (23 feet) across, about the size of a duck boat.
Had 2012 KT42 actually entered the Earth's atmosphere, its relatively small size and likely weak structure probably would have caused it to be destroyed before it had a chance to cause damage on the surface. Perhaps only a few fragments would have reached the ground as meteorites.