An Earth-grazing fireball (or Earth grazer) is a fireball, a very bright meteor that enters Earth’s atmosphere and leaves again. Some fragments may impact Earth as meteorites, if the meteor starts to break up or explodes in mid-air. These phenomena are then called Earth-grazing meteor processions and bolides. Famous examples of Earth-grazers are the 1972 Great Daylight Fireball and the Meteor Procession of July 20, 1860.
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 from its orbit as it encountered Earth's atmosphere.
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.
Known Earth-grazing fireballs
An Earth-grazing fireball is a rarely measured kind of fireball caused by a meteoroid that collides with the Earth but survives the collision by passing through, and exiting, the atmosphere. As of 2008[update] four grazers have been scientifically observed.
- Meteor procession of July 20, 1860
- Meteor procession of February 9, 1913 led to conclusions a temporary satellite capture of Earth had broken up
- 1972 Great Daylight Fireball, August 10, 1972, US19720810 at 15 km/s above United States and Canada (first scientific observation). It was estimated to have lost about half its mass, and 8 km/s of velocity during the encounter.
- October 13, 1990, a 40 kilogram, 41.5 km/s meteoroid passed at 97.9 km above Czechoslovakia (first orbit calculation based on photographic records from two distant places).
- March 29, 2006, fireball passed 18.8 km/s through the atmosphere 71.4 km above Japan
- August 7, 2007, EN070807 passed through the atmosphere over Europe with an orbit belonging to the rare Aten asteroid type
- June 10, 2012, an Earth-grazing fireball from the Daytime ζ-Perseid shower passed over Spain, travelling 510 km in the atmosphere. It was the faintest Earth-grazing meteor reported in the scientific literature and the first one belonging to a meteor shower.
- December 24, 2014, a slow moving Christmas Eve fireball SPMN241214 passed over north Africa, Spain, and Portugal, travelling about 1,200 km in the atmosphere.
- July 7, 2017, the Desert Fireball Network observed a grazing fireball that traveled over 1300 km through the atmosphere above Western Australia and South Australia. The closest approach was about 58.5km, and the initial mass is estimated to be a minimum of ~60 kg. The meteoroid came from an Apollo-type orbit, and due to the close encounter with the Earth, it was sent onto a Jupiter-family comet-like orbit.
- List of asteroid close approaches to Earth
- List of Earth-crossing minor planets
- Asteroid impact prediction
- "Texas State astronomers solve Walt Whitman meteor mystery : University News Service : Texas State University". Archived from the original on 2011-10-19. Retrieved 2013-10-19.. Txstate.edu (2010-05-28). Retrieved on 2013-10-19.
- Nemiroff, R.; Bonnell, J., eds. (2 March 2009). "Earthgrazer: The Great Daylight Fireball of 1972". Astronomy Picture of the Day. NASA. Retrieved 2013-10-19. Cite has empty unknown parameter:
- "Images of Harper's Weekly front page story". Archived from the original on 2014-04-28. Retrieved 2017-08-26.
- 150-year-old meteor mystery solved
- US19720810 (Daylight Earth grazer) Archived March 7, 2004, at the Wayback Machine Global Superbolic Network Archive, 2000, 'Size: 5 to 10 m' Cite error: The named reference "gsna" was defined multiple times with different content (see the help page).
- Daylight Fireball of August 10, 1972 C. Kronberg, Munich Astro Archive, archived summary by Gary W. Kronk of early analysis and of Zdeněk Ceplecha's paper for Astronomy and Astrophysics in 1994, '3 meters, if a carbonaceous chondrite, or as large as 14 meters, if composed of cometary materials', 'post-encounter ... 2 or 10 meters'
- Spurný, P.; Ceplecha, Z.; Borovicka, J. Earth-grazing fireball: Czechoslovakia, Poland, October 13, 1990, 03h27m16sUT. WGN, Vol. 19, Nr. 1, p. 13; (aphelion of its orbit changed from 2.80 AU to 1.80 AU)
- Spurný, P. Spurný; J. Borovička; Z. Ceplecha; L. Shrbený (2008). "Precise Multi-instrument Data on 45 Fireballs Recorded over Central Europe in the Period 2006-2008" (PDF). Asteroids, Comets, Meteors. Czech Republic: Astronomical Institute of the Academy of Sciences, Fričova 298, CZ-251 65 Ondřejov Observatory. 1405: 8217. Bibcode:2008LPICo1405.8217S. Archived (PDF) from the original on 2016-03-03. Retrieved 2008-07-06.
EN070807 fireball ... very rare Earth-grazing fireball ... Aten type
- Although other grazers have been seen and, rarely, photographed, without specialised scientific observations their orbits cannot be determined. An example is the Leonid grazer over Hawaii on 2001-11-18 -Abe 2006 (PDF)
- O'Keefe, John A. 1959. A Probable Natural Satellite: The Meteor procession of February 9, 1913. Journal of the Royal Astronomical Society of Canada, Vol. 53, p.59. Code 1959JRASC..53...59O. Retrieved 2008-07-07
- Abe 2006 (abstract)
- Abe 2006 (PDF) approximately 100 kg, orbit aphelion reaches Jupiter
- EN indicates the European Fireball Network
- Madiedo, José M.; Espartero, Francisco; Castro-Tirado, Alberto J.; Pastor, Sensi; de los Reyes, José A. (2016). "An Earth-grazing fireball from the Daytime ζ-Perseid shower observed over Spain on 2012 June 10" (PDF). Monthly Notices of the Royal Astronomical Society. 460 (1): 917–922. arXiv:1604.08380. Bibcode:2016MNRAS.460..917M. doi:10.1093/mnras/stw1020.
- Moreno, A.; Madiedo, J. M.; Zamorano, J.; et al. (March 2016). "Preliminary Spectroscopic and Dynamical Analysis of an Earth-Grazer Fireball Observed on December 24, 2014" (PDF). 47th Lunar and Planetary Science Conference, held March 21-25, 2016 at The Woodlands, Texas. p. 1088. Bibcode:2016LPI....47.1088M. Archived (PDF) from the original on November 28, 2016. Retrieved November 27, 2016.
The dictionary definition of Earth-grazing at Wiktionary