The Russian Meteor That Blew Out Windows Across Six Hundred Square Kilometres in 2013

At 09:20 local time on the morning of 15 February 2013, a 20-metre stony asteroid weighing approximately 12,000 tonnes entered Earth’s atmosphere from the east-southeast at a velocity of approximately 19 kilometres per second. It travelled obliquely across the southern Russian Urals on a shallow trajectory of about 18 degrees from horizontal, reached approximately 30 kilometres altitude over the city of Chelyabinsk, and exploded with the energy of approximately 440 kilotons of TNT — about 26 times the energy of the Hiroshima bomb. The visible fireball was approximately as bright as the sun at the moment of peak luminosity.

It was the largest atmospheric impact event since the Tunguska explosion of 1908 — about a thirtieth the size of Tunguska, but in this case directly above a major city of approximately 1.1 million people. It injured approximately 1,500 people, mostly from flying glass when the shockwave reached the ground. It was captured on approximately 400 separate Russian car-dashboard cameras and surveillance cameras, producing the most thoroughly-documented atmospheric impact event in human history.

The trajectory

The asteroid’s pre-impact orbit has been substantially reconstructed from the camera-network and seismic data. It was a member of the Apollo asteroid family — a group of near-Earth asteroids on orbits that cross Earth’s orbit — and had probably split off from a larger parent body approximately 1.2 million years before the impact. Its specific orbital characteristics suggest substantial gravitational interaction with Mercury and Venus during the preceding several centuries; the precise approach orbit that brought it to Earth had not been gravitationally predictable more than a few decades in advance with the surveillance technology available before 2013.

The asteroid was not detected by any pre-impact surveillance system. The standard near-Earth-asteroid monitoring infrastructure (the NASA Near-Earth Object Program, the European Space Agency’s parallel programs, the various amateur astronomical contributions) had detected approximately 90% of the >1 km near-Earth asteroids by 2013 but only approximately 1% of the 20-50 m population to which the Chelyabinsk impactor belonged. The Chelyabinsk size class is the most consequential single category of currently-monitored impact threat: the >1 km category includes potentially civilization-ending objects but is now well-mapped (with no currently-known imminent threats); the 20-50 m category includes objects that would each substantially damage a major city if they impacted in the wrong place and is substantially un-monitored.

The blast

The atmospheric airburst at 30 km altitude was substantially the standard physics of a high-altitude bolide. The asteroid’s velocity at atmospheric entry exceeded the local sound speed by a factor of approximately 60, producing a shockwave that compressed and heated the surrounding atmosphere to several thousand degrees. The asteroid’s internal stress at the peak compression exceeded its tensile strength; the object substantially shattered at approximately 25-30 km altitude and converted its remaining kinetic energy into thermal radiation and atmospheric shockwave over approximately a second.

The thermal pulse was sufficient to substantially raise the surface temperature in the Chelyabinsk metropolitan area for several seconds — substantial enough that an observer noted his face had been mildly sunburned by the light from inside a passing tram. The visible fireball persisted for approximately 16 seconds.

The acoustic shockwave reached the surface approximately 90 seconds after the visible flash (the standard travel time for the 30 km altitude difference at sound speed). The peak overpressure at ground level in the Chelyabinsk metropolitan area was approximately 3 kPa — sufficient to break double-glazed windows over an area of approximately 6,000 square kilometres. Approximately 7,200 buildings were damaged, almost entirely from broken glass. The 1,500 injured persons were substantially treated for lacerations from flying glass; approximately 100 were hospitalised; no immediate deaths were directly attributed to the impact.

A substantial fragment of the asteroid — approximately 650 kilograms, the largest single recovered piece — survived the airburst and impacted Lake Chebarkul (approximately 70 km west of Chelyabinsk) at approximately 09:21 local time. The lake was frozen; the impactor punched a hole approximately 8 metres across in the ice and sank into the lakebed. The fragment was recovered by Russian divers in October 2013 and is now displayed at the Chelyabinsk State Museum of Local History. Approximately 100 additional substantially smaller fragments — totalling perhaps 700 kilograms — have been recovered from the area between Chelyabinsk and Chebarkul by amateur meteorite-hunters and academic teams.

What it changed

The Chelyabinsk event substantially changed the institutional politics of near-Earth-object surveillance. NASA had been operating the Near-Earth Object Observations Program since 1998 with a substantially-modest annual budget; the program’s funding tripled in the years following Chelyabinsk and the program was reorganised as the Planetary Defense Coordination Office in 2016. The European Space Agency established a parallel Planetary Defense Office in 2014. The international International Asteroid Warning Network — a coordinating body for substantially independent national NEO-monitoring programs — was founded in 2013, with the Chelyabinsk event as its formative justification.

The substantive surveillance gap that Chelyabinsk exposed — the 20-50 m near-Earth-asteroid population that current ground-based optical telescopes cannot reliably detect — remains largely unmapped. The proposed NEO Surveyor infrared space telescope, designed substantially to address the 30-50 m detection gap, was approved by NASA in 2019 and is currently scheduled for launch in 2027 (subject to budget renegotiations). The NEO Surveyor’s projected operational capability would detect approximately 90% of the 20-50 m near-Earth asteroid population within a decade of operation.

The first successful kinetic-impact asteroid-deflection test — NASA’s DART (Double Asteroid Redirection Test) mission, which deliberately collided with the small moonlet Dimorphos around the asteroid Didymos on 26 September 2022 — was institutionally driven substantially by the post-Chelyabinsk political momentum for active planetary-defence capabilities. The DART impact altered Dimorphos’s orbit by approximately 32 minutes, demonstrating proof-of-concept for kinetic asteroid deflection at the small-asteroid scale.

The Chelyabinsk event killed nobody. It exposed the scale of the contemporary atmospheric-impact threat in a way that no theoretical analysis had been able to do. The video evidence — the bright fireball over a snow-covered Russian morning, the car dashboards continuing to record the trip to work, the shockwave breaking glass in slow-motion footage — substantially changed the public perception of asteroid risk from a theoretical concern to a concrete observational fact. The next Tunguska-scale event — predicted to occur approximately once every 100-300 years on average — will probably not be a surprise on the same scale.