Earth-grazing fireball

Frederic Edwin Church, "The Meteor of 1860". 150 years later in 2010 it was determined to be an Earth-grazing meteor procession.^[1]

An Earth-grazing fireball (or Earth-grazer)^[2] is a small solar system body (SSSB) that enters the Earth's atmosphere and leaves again. If it starts to break up in the atmosphere it can become an Earth-grazing meteor procession, and some fragments may impact the Earth and become a meteorite.^[1] Famous examples of this are the 1972 Great Daylight Fireball and the Meteor Procession of July 20, 1860.^[1][3][4]

Overview

As an Earth-grazer passes through the atmosphere its mass and velocity are changed, so that its orbit, as it re-enters space, will be different than its orbit as it encountered Earth's atmosphere.^[5][6][7]

There is no exact criterion for passing by outside of the atmosphere, except perhaps roughly 80 km (50 mi) up, or the Kármán line at 100 km (62 mi).^{[citation needed]} There is no agreed-upon end to the upper atmosphere, but rather incrementally thinner air from the stratosphere (~50 km), mesosphere (~85 km), and thermosphere (~690 km) up to the exosphere (~10,000) (see also thermopause). For example, a meteoroid can become a meteor at an altitude of 85–120 km above the Earth.

The term Earth-grazer or inner-grazer is also sometimes used for an asteroid or meteoroid whose orbit brings it close to Earth (such as within a Lunar distance).^{[citation needed]}

An SSSB with a grazing orbit does not necessarily make contact with the Earth's atmosphere, although it may be more likely to collide with it (see List of Earth-crossing minor planets and Outer-grazer).^{[citation needed]}

Known Earth-grazing fireballs

An Earth-grazing fireball is a rarely measured kind of fireball^[8] caused by a meteoroid that collides with the Earth but survives the collision by passing through, and exiting, the atmosphere. As of 2008 four grazers have been scientifically observed.^[9]

• Meteor procession of July 20, 1860 ^[1][3][4]
• Meteor procession of February 9, 1913 led to conclusions a temporary satellite capture of Earth had broken up^[10]
• 1972 Great Daylight Fireball, August 10, 1972, US19720810 at 15 km/s above United States and Canada (first scientific observation).
• October 13, 1990, a 40 kilogram, 41.5 km/s meteoroid passed at 97.9 km above Czechoslovakia^[7]
• March 29, 2006, fireball passed 18.8 km/s through the atmosphere 71.4 km above Japan^[11][12]
• August 7, 2007, EN070807 passed through the atmosphere over Europe with an orbit belonging to the rare Aten asteroid type^[8][13]

See also

• List of Earth-crossing minor planets
• List of asteroid close approaches to Earth
• Near-Earth object

References

External links

• Fireball of 1860 (painting)
• Fireball of 1972 (photo)

v t e Modern impact events Pre–2000 1490 Ch'ing-yang event 1783 Great Meteor 1860 Great Meteor 1908 Tunguska event 1913 Great Meteor Procession 1930 Curuçá River event 1947 Sikhote-Alin meteorite 1969 Murchison meteorite 1972 Great Daylight Fireball 1994 Cando event Post–2000 2002 Eastern Mediterranean event 2002 Vitim event 2007 Carancas impact event 2008 TC3 impact 2009 Sulawesi superbolide 2012 Sutter's Mill meteorite 2012 UK meteoroid 2013 Chelyabinsk meteor Chelyabinsk meteorite 2013 Montreal bolide 2014 AA impact Jupiter 1994 Comet Shoemaker–Levy 9 impact 2009 Jupiter impact event 2010 Jupiter impact event Lists List of meteor air bursts List of asteroid close approaches to Earth Lists of comets List of minor planets List of Earth-crossing minor planets Meteorite fall See also Asteroid impact avoidance B612 Foundation Bolide Earth-grazing fireball Meteor procession Meteor shower Meteorite Meteoroid Near-Earth object Potentially hazardous object Spaceguard

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