The sensor record of airbursts
How satellites and microphones keep a running tally of space rocks exploding in our sky.
Key facts
- When
- 1988 to the present
- Where
- Worldwide
- What hit
- most about 1 to 10 m across
- Era
- The sensor age, 2000 onwards
Most from a tenth of a kiloton to a few kilotons; roughly every year or two one of several kilotons; rarely, tens to hundreds.
Earth is hit by small asteroids far more often than most people realise.
What happened
Since 1988, US government satellites designed to watch for missile launches and nuclear explosions have also recorded bright fireballs, and their timings, positions, speeds and energies are released to scientists. More than a thousand events have been listed. A worldwide network of infrasound stations, built to check that countries keep to the nuclear test-ban treaty, hears many of the same blasts.
Some of the largest in the record are the Chelyabinsk airburst of 2013 (about 440 to 500 kilotons), the Bering Sea blast of 2018 (about 173 kilotons), the Bone airburst in Indonesia in 2009 (about 30 to 50 kilotons), an explosion east of Japan on Christmas Day 2010 (about 33 kilotons), the Eastern Mediterranean event of 2002 (about 12 to 26 kilotons), and one over the Southern Ocean off Antarctica in 2004 (about 12 kilotons), whose dust trail was photographed from space.
Before satellites, the record relies on infrasound and eyewitnesses, as with the 1963 blast in the southern Indian Ocean, and on physical traces, as at Tunguska in 1908.
Effects
Nearly all happen over the oceans, which cover most of the planet, or over empty land, and cause no harm. Chelyabinsk is the exception that shows what a blast of a few hundred kilotons can do near a city.
The evidence
Satellite detections of the flash, infrasound records, and camera networks for smaller events.
Did you know?
Before the sensor record, Chelyabinsk-sized airbursts were thought to happen about once a century; the record suggests they may be several times more common.
One of the fastest fireballs in the record, over China in 2015, hit the atmosphere at about 49 km per second.
Related pages
How is impact energy measured? See energy explained, or try the impact calculator.