The Chelyabinsk asteroid over Russia on February 15, 2013 was a “small asteroid” estimated at 20 meters across. Small, yet credited with shattering windows in 7,200 buildings over 6 cities, and injuring 1,500 people.
On November 14, 2014 NASA released a map produced by the Near Earth Object (NEO) program showing 556 small asteroid atmosphere “hits” from 1994-2013. Almost all of them “burned up”, and were classified as “fireballs”. Fireballs or bright meteors are known by the term “bolide”. The map below illustrates bolide events as universal – the orange dots are day, and blue night. Size difference in dots pertain to “optical radiant energy”. I’m no scientist, and fear my explanation of the term might fall flat – the link below is helpful in that respect.
NASA announced the Asteroid Redirect Mission (ARM) in June 2014, a ambitious program aimed to identify, capture, and redirect potentially hazardous asteroids to an orbit around the Moon. See link below…
On a grander scale, all objects greater than 100 meters and orbiting or likely to orbit Earth within 100 Lunar Distance (LD) – 1 LD being the distance from Earth to the Moon, are called Potentially Hazardous Asteroids (PHA) – as of today 1512 of these objects are being monitored.
View larger | Bolide events, 1994-2013. A bolide is what most people would call a fireball or very bright meteor. Map shows location of atmospheric impacts from small asteroids about 1 meter (3 feet) to almost 20 meters (60 feet) in size. It shows 556 separate events in a 20-year period. Orange dots indicate daytime events; blue dots indicate nighttime events. Sizes of dots are proportional to the optical radiated energy of events. Image via Planetary Science