Abolide is normally taken to mean an exceptionally brightmeteor, but the term is subject to more than one definition, according to context. It may refer to any largecrater-forming body, or to one that explodes in theatmosphere. It can be a synonym for afireball, sometimes specific to those with anapparent magnitude of −4 or brighter.
Bolide from the French astronomy bookLe Ciel; Notions 'Elémentaires d'Astronomie Physique (1877)
The wordbolide (/ˈboʊlaɪd/; fromItalian viaLatin, from Ancient Greekβολίς (bolís)'missile'[2][3]) may refer to somewhat different phenomena depending on the context in which the word appears, and readers may need to make inferences to determine which meaning is intended in a particular publication.[4] An early usage occurs inNatural History, where Pliny the Elder describes two types ofprodigies, "those which are called lampades and those which are called bolides".[5] At least one of the prodigies described by Pliny (a "spark" that fell, grew to the "size of the moon", and "returned into the heavens"[6]) has been interpreted by astronomers as a bolide in the modern sense.[7] His description of an object coming near the earth and continuing back into the sky matches the expected trajectory of a fireball crossing above an observer.[8] A 1771 fireball that burst aboveMelun, France, was widely discussed by contemporary astronomers as a "bolide" and was the subject of an officialFrench Academy of Sciences investigation led byJean-Baptiste Le Roy.[9] In 1794,Ernst Chladni published a book proposing that meteors were small objects that fell to Earth from space and that small bodies existed in space beyond the moon. Though initially ridiculed, Chladni's book became the starting point for the modern field ofmeteoritics.[10]
Astronomers use the word to describe any extremely brightmeteor (or fireball), especially one that explodes in the atmosphere.[4] Some astronomical definitions specify anapparent magnitude of −4 or brighter.[11] A superbolide reaches an apparent magnitude of −17 or brighter,[11][12] which is about 51 times brighter than the full moon. Recent examples of superbolides include theSutter's Mill meteorite in California and theChelyabinsk meteor in Russia.
Geologists use the word to describe a very largeimpact event.[4] The geological definition covers any generic largecrater-forming impacting body whose composition (for example, whether it is a rocky or metallicasteroid, or an icycomet) is unknown.[13]
TheIAU has no official definition of "bolide", and generally considers the term synonymous withfireball, a brighter-than-usualmeteor; however, the term generally applies to fireballs reaching anapparent magnitude −4 or brighter.[11] Astronomers tend to usebolide to identify an exceptionally bright fireball, particularly one that explodes (sometimes called a detonating fireball).[14] It may also be used to mean afireball that is audible.
Geologists use the termbolide differently fromastronomers. Ingeology, it indicates a very largeimpactor. For example, theWoods Hole Coastal and Marine Science Center of theUSGS usesbolide for any large crater-forming impacting body whose origin and composition is unknown, as, for example, whether it was astony ormetallic asteroid, or a less dense, icy comet made ofvolatiles, such as water, ammonia, and methane.[13]
The most notable example is the bolide that caused theChicxulub crater in Mexico, 66 million years ago. Scientific consensus agrees that this event directly led to the extinction of all non-aviandinosaurs, and it is evidenced by a thin layer ofiridium found at that geological layer marking theK–Pg boundary.
^Pliny the Elder, The Natural History, BOOK II.We have an account of a spark falling from a star, and increasing as it approached the earth, until it became of the size of the moon, shining as through a cloud; it afterwards returned into the heavens and was converted into a lampas; this occurred in the consulship of Cn. Octavius and C. Scri- bonius. It was seen by Silanus, the proconsul, and his attendants.
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