The fireball was caused by a small asteroid hitting Earth's atmosphere at a shallow angle. Preliminary infrasound measurements place the energy of the blast at 20 tons of TNT (0.02 kton), with considerable uncertainty. Bill Cooke of NASA's Meteoroid Environment Office estimates that the space rock was about 1 meter wide and massed some 1260 kg. "Fireballs of this size are surprisingly common," he notes. "They hit Earth about 14 times a month, on average, although most go unnoticed because they appear during the day or over unpopulated areas."

Many readers have asked if fragments of the meteoroid might have reached Earth. The answer is "yes." Cooke advises looking directly underneath the fireball's debris trail, which was pinged by National Weather Service radars in Iowa.

Not a gamma Virginid: Contrary to some reports, this fireball was not a member of the gamma Virginid meteor shower, a minor shower that peaks in mid-April. The fireball's timing and trajectory do not match what would be expected for a gamma Virginid.

Fonte: spaceweather.com