A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or moon. When the object enters the atmosphere, various factors such as friction and chemical interactions with the atmospheric gases cause it to heat up and radiate that energy, it becomes a meteor and forms a fireball known as a shooting star or falling star. Meteorites vary in size. For geologists, a bolide is a meteorite large enough to create an impact crater. Meteorites that are recovered after being observed as they transit the atmosphere and impact the Earth are called meteorite falls. All others are known as meteorite finds; as of August 2018, there were about 1,412 witnessed falls that have specimens in the world's collections. As of 2018, there are more than 59,200 well-documented meteorite finds. Meteorites have traditionally been divided into three broad categories: stony meteorites that are rocks composed of silicate minerals.
Modern classification schemes divide meteorites into groups according to their structure and isotopic composition and mineralogy. Meteorites smaller than 2 mm are classified as micrometeorites. Extraterrestrial meteorites are such objects that have impacted other celestial bodies, whether or not they have passed through an atmosphere, they have been found on the Mars. Meteorites are always named for the places they were found a nearby town or geographic feature. In cases where many meteorites were found in one place, the name may be followed by a number or letter; the name designated by the Meteoritical Society is used by scientists and most collectors. Most meteoroids disintegrate. Five to ten a year are observed to fall and are subsequently recovered and made known to scientists. Few meteorites are large enough to create large impact craters. Instead, they arrive at the surface at their terminal velocity and, at most, create a small pit. Large meteoroids may strike the earth with a significant fraction of their escape velocity, leaving behind a hypervelocity impact crater.
The kind of crater will depend on the size, degree of fragmentation, incoming angle of the impactor. The force of such collisions has the potential to cause widespread destruction; the most frequent hypervelocity cratering events on the Earth are caused by iron meteoroids, which are most able to transit the atmosphere intact. Examples of craters caused by iron meteoroids include Barringer Meteor Crater, Odessa Meteor Crater, Wabar craters, Wolfe Creek crater. In contrast relatively large stony or icy bodies like small comets or asteroids, up to millions of tons, are disrupted in the atmosphere, do not make impact craters. Although such disruption events are uncommon, they can cause a considerable concussion to occur. Large stony objects, hundreds of meters in diameter or more, weighing tens of millions of tons or more, can reach the surface and cause large craters, but are rare; such events are so energetic that the impactor is destroyed, leaving no meteorites. Several phenomena are well documented during witnessed meteorite falls too small to produce hypervelocity craters.
The fireball that occurs as the meteoroid passes through the atmosphere can appear to be bright, rivaling the sun in intensity, although most are far dimmer and may not be noticed during daytime. Various colors have been reported, including yellow and red. Flashes and bursts of light can occur. Explosions and rumblings are heard during meteorite falls, which can be caused by sonic booms as well as shock waves resulting from major fragmentation events; these sounds can be heard with a radius of a hundred or more kilometers. Whistling and hissing sounds are sometimes heard, but are poorly understood. Following passage of the fireball, it is not unusual for a dust trail to linger in the atmosphere for several minutes; as meteoroids are heated during atmospheric entry, their surfaces experience ablation. They can be sculpted into various shapes during this process, sometimes resulting in shallow thumbprint-like indentations on their surfaces called regmaglypts. If the meteoroid maintains a fixed orientation for some time, without tumbling, it may develop a conical "nose cone" or "heat shield" shape.
As it decelerates the molten surface layer solidifies into a thin fusion crust, which on most meteorites is black. On stony meteorites, the heat-affected zone is at most a few mm deep. Reports vary. Meteorites from multiple falls, such as Bjurbole, Tagish Lake, Buzzard Coulee, have been found having fallen on lake and sea ice suggesting that they were not hot when they
The Vesta family is a family of asteroids. The cratering family is located in the inner asteroid belt in the vicinity of its namesake and principal body, 4 Vesta, it is one of the largest asteroid families with more than 15,000 known members and consists of bright V-type asteroids, so-called "vestoids". The Vestian asteroids consist of 4 Vesta, the second-most-massive of all asteroids, many small asteroids below 10 km diameter; the brightest of these, 1929 Kollaa and 2045 Peking, have an absolute magnitude of 12.2, which would give them a radius of about 7.5 km assuming the same high albedo as 4 Vesta. The family originated from an impact on asteroid 4 Vesta, with the giant south-polar crater the impact site; the family are thought to be the source of the HED meteorites. The Vesta family includes a few J-type asteroids, which are thought to have come from the deeper layers of Vesta's crust, are similar to the diogenite meteorites A HCM numerical analysis determined a large group of'core' family members, whose proper orbital elements lie in the approximate ranges This gives the approximate boundaries of the family.
At the present epoch, the range of osculating orbital elements of these core members is The Zappala 1995 analysis found 235 core members. A search of a recent proper-element database for 96944 minor planets in 2005 yielded 6051 objects lying within the Vesta-family region as per the first table above. Spectroscopic analyses have shown, they have similar orbital elements by coincidence. These include 306 Unitas, 442 Eichsfeldia, 1697 Koskenniemi, 1781 Van Biesbroeck, 2024 McLaughlin, 2029 Binomi, 2086 Newell, 2346 Lilio, others.. Zappalà, Vincenzo. 158, p. 106. Data set online here. AstDys site. Proper elements for 96944 numbered minor planets
Glossary of meteoritics
This is a glossary of terms used in meteoritics, the science of meteorites. 2 Pallas – an asteroid from the asteroid belt and one of the parent bodies of the CR meteorites. 4 Vesta – second-largest asteroid in the asteroid belt and source of the HED meteorites. 221 Eos – an asteroid from the asteroid belt and one of the parent bodies of the CO meteorites. 289 Nenetta – an asteroid from the asteroid belt and one of the parent bodies of the angrites. 3103 Eger – an asteroid from the asteroid belt and one of the parent bodies of the aubrites. 3819 Robinson – an asteroid from the asteroid belt and one of the parent bodies of the angrites. IA meteorite – an iron meteorite group now part of the IAB group/complex. IAB meteorite – an iron meteorite and primitive achondrite of the IAB group/complex. IB meteorite – an iron meteorite group now part of the IAB group/complex. IC meteorite – an iron meteorite, part of the IC group. Ablation – the process of a meteorite losing mass during the passage through the atmosphere.
Acapulcoite – a group of primitive achondrites. Accretion – the process in which matter of the protoplanetary disk coalesces to form planetesimals. Achondrite – a differentiated meteorite. Aerolite – an old term for stony meteorites. ALH – an abbreviation used for meteorites from Allan Hills. Allan Hills – a mountain chain in Antarctica where meteorites are concentrated by ice movements and can be spotted in the snow. Allan Hills 84001 – is an exotic meteorite from Mars that does not fit into any of the SNC groups and was thought to contain evidence for life on Mars. Allende meteorite – is the largest carbonaceous chondrite found on Earth. Amphoterite – an obsolete classification of chondritic meteorites that are now classified as LL. Angrite – a basaltic meteorite. Anomalous – meteorites that have properties that are unusual for their group or grouplet. ANSMET – the ANtarctic Search for METeorites is scientific program that looks for meteorites in the Transantarctic Mountains. Asteroidal achondrite – an achondrite that differentiated on an asteroid or planetesimal Asteroid spectral types – classification of asteroids according to their spectra.
Ataxite – an iron meteorite that has no visible structures when etched. Basaltic achondrite – a grouping of basalt meteorites Brachinite – either a primitive achondrite or an asteroidal achondrite C – can refer to carbonaceous chondrite or to an iron meteorite designation. Carbonaceous chondrite CAI – an abbreviation of Calcium-aluminium-rich inclusion Calcium-aluminium-rich inclusion Chassignite Chondrite – stony meteorites unmodified by melting or differentiation of the parent body Chondrule – millimetre-scale round grains found in chondrites Clan – meteorites that are not similar enough to form a group, but are not too different from each other to be put in separate classes. Class – two or more groups that have a similar chemistry and oxygen isotope ratios. Compositional type – a classification based on overall composition, for example stony, stony-iron. Can refer to the composition deduced from spectroscopy of asteroids. Condensation – the process of chemicals changing from the gaseous to the solid phase during the cooling of the protoplanetary disk.
Condensation sequence – the sequence of minerals that changes from the gaseous to the solid state while the protoplanetary disk cools. Cosmic dust – small interplanetary and interstellar particles that are similar to meteorites. Cosmochemistry – the science of the chemistry of the Solar System, based in part on the chemistry of meteorites. Dar al Gani – a meteorite field in the Libyan Sahara. Desert glass – natural glass found in deserts formed from the silica in sand as a result of lightning strikes or meteor impacts. Differentiated – a meteorite that has undergone igneous differentiation. Differentiation – the process of a planetesimal forming an iron core and silicate mantle. Duo – a grouping of two meteorites that share similar characteristics. E -- can refer to an iron meteorite designation. Eagle Station grouplet – a set of pallasite meteorite specimen that don't fit into any of the defined pallasite groups. Electrophonic bolide – a meteoroid which produces a measurable discharge of electromagnetic energy during its passage through the atmosphere.
Enstatite achondrite – a meteorite, composed of enstatite. Part of the aubrite group. Enstatite chondrite – a rare form of meteorite thought to comprise only 2% of chondrites. Fall – a meteorite, seen while it fell to Earth and found. Find – a meteorite, found without seeing it fall. Fossil meteorite - a meteorite, buried under layers of sediment before the start of the Quaternary period; some or all of the original cosmic material has been replaced by diagenetic minerals.. Fragment – a part of a meteorite that broke during passage through the atmosphere. Fragmentation – the process in which a meteorite breaks while falling through the atmosphere. Fusion crust – a coating on meteorites that forms during their passage through the atmosphere. Group – a collection of more than 5 meteorites sharing similar characteristics. Grouplet – a collection of less than 5 meteorites sharing similar characteristics. HED – abbreviation for three basaltic achondrite groups howardite and diogenite. HED meteorite – a clan of basaltic achondrites.
Hexahedrite – a structural class of iron meteorites having a low nickel content Hunter – a person who searches for meteorites. Impact breccia – rock composed of fragm
Earth is the third planet from the Sun and the only astronomical object known to harbor life. According to radiometric dating and other sources of evidence, Earth formed over 4.5 billion years ago. Earth's gravity interacts with other objects in space the Sun and the Moon, Earth's only natural satellite. Earth revolves around the Sun in a period known as an Earth year. During this time, Earth rotates about its axis about 366.26 times. Earth's axis of rotation is tilted with respect to its orbital plane; the gravitational interaction between Earth and the Moon causes ocean tides, stabilizes Earth's orientation on its axis, slows its rotation. Earth is the largest of the four terrestrial planets. Earth's lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. About 71% of Earth's surface is covered with water by oceans; the remaining 29% is land consisting of continents and islands that together have many lakes and other sources of water that contribute to the hydrosphere.
The majority of Earth's polar regions are covered in ice, including the Antarctic ice sheet and the sea ice of the Arctic ice pack. Earth's interior remains active with a solid iron inner core, a liquid outer core that generates the Earth's magnetic field, a convecting mantle that drives plate tectonics. Within the first billion years of Earth's history, life appeared in the oceans and began to affect the Earth's atmosphere and surface, leading to the proliferation of aerobic and anaerobic organisms; some geological evidence indicates. Since the combination of Earth's distance from the Sun, physical properties, geological history have allowed life to evolve and thrive. In the history of the Earth, biodiversity has gone through long periods of expansion punctuated by mass extinction events. Over 99% of all species that lived on Earth are extinct. Estimates of the number of species on Earth today vary widely. Over 7.6 billion humans live on Earth and depend on its biosphere and natural resources for their survival.
Humans have developed diverse cultures. The modern English word Earth developed from a wide variety of Middle English forms, which derived from an Old English noun most spelled eorðe, it has cognates in every Germanic language, their proto-Germanic root has been reconstructed as *erþō. In its earliest appearances, eorðe was being used to translate the many senses of Latin terra and Greek γῆ: the ground, its soil, dry land, the human world, the surface of the world, the globe itself; as with Terra and Gaia, Earth was a personified goddess in Germanic paganism: the Angles were listed by Tacitus as among the devotees of Nerthus, Norse mythology included Jörð, a giantess given as the mother of Thor. Earth was written in lowercase, from early Middle English, its definite sense as "the globe" was expressed as the earth. By Early Modern English, many nouns were capitalized, the earth became the Earth when referenced along with other heavenly bodies. More the name is sometimes given as Earth, by analogy with the names of the other planets.
House styles now vary: Oxford spelling recognizes the lowercase form as the most common, with the capitalized form an acceptable variant. Another convention capitalizes "Earth" when appearing as a name but writes it in lowercase when preceded by the, it always appears in lowercase in colloquial expressions such as "what on earth are you doing?" The oldest material found in the Solar System is dated to 4.5672±0.0006 billion years ago. By 4.54±0.04 Bya the primordial Earth had formed. The bodies in the Solar System evolved with the Sun. In theory, a solar nebula partitions a volume out of a molecular cloud by gravitational collapse, which begins to spin and flatten into a circumstellar disk, the planets grow out of that disk with the Sun. A nebula contains gas, ice grains, dust. According to nebular theory, planetesimals formed by accretion, with the primordial Earth taking 10–20 million years to form. A subject of research is the formation of some 4.53 Bya. A leading hypothesis is that it was formed by accretion from material loosed from Earth after a Mars-sized object, named Theia, hit Earth.
In this view, the mass of Theia was 10 percent of Earth, it hit Earth with a glancing blow and some of its mass merged with Earth. Between 4.1 and 3.8 Bya, numerous asteroid impacts during the Late Heavy Bombardment caused significant changes to the greater surface environment of the Moon and, by inference, to that of Earth. Earth's atmosphere and oceans were formed by volcanic outgassing. Water vapor from these sources condensed into the oceans, augmented by water and ice from asteroids and comets. In this model, atmospheric "greenhouse gases" kept the oceans from freezing when the newly forming Sun had only 70% of its current luminosity. By 3.5 Bya, Earth's magnetic field was established, which helped prevent the atmosphere from being stripped away by the solar wind. A crust formed; the two models that explain land mass propose either a steady growth to the present-day forms or, more a rapid growth early in Earth history followed by a long-term steady continental area. Continents formed by plate tectonics
Diogenites are a group of the HED meteorite clan, a type of achondritic stony meteorites. Diogenites are believed to originate from deep within the crust of the asteroid 4 Vesta, as such are part of the HED meteorite clan. There are about 40 distinct members known. Diogenites are composed of igneous rocks of plutonic origin, having solidified enough deep within Vesta's crust to form crystals which are larger than in the eucrites; these crystals are magnesium-rich orthopyroxene, with small amounts of plagioclase and olivine. Diogenites are named for Diogenes of Apollonia, an ancient Greek philosopher, the first to suggest an outer space origin for meteorites. Glossary of meteoritics Vesta family Diogenite images - Meteorites Australia
An achondrite is a stony meteorite that does not contain chondrules. It consists of material similar to terrestrial basalts or plutonic rocks and has been differentiated and reprocessed to a lesser or greater degree due to melting and recrystallization on or within meteorite parent bodies; as a result, achondrites have distinct mineralogies indicative of igneous processes. Achondrites account for about 8% of meteorites overall, the majority of them are HED meteorites originating from the crust of asteroid 4 Vesta. Other types include Martian and several types thought to originate from as-yet unidentified asteroids; these groups have been determined on the basis of e.g. the Fe/Mn chemical ratio and the 17O/18O oxygen isotope ratios, thought to be characteristic "fingerprints" for each parent body. Achondrites are classified into the following groups: Primitive achondrites Asteroidal achondrites Lunar meteorites Martian meteorites Primitive achondrites called PAC group, are called in this way because their chemical composition is primitive in the sense that it is similar to the composition of chondrites, but their texture is igneous, indicative of melting processes.
To this group belong: Acapulcoites Lodranites Winonaites Ureilites Brachinites Asteroidal achondrites called evolved achondrites, are called in this way because have been differentiated on a parent body. This means that their mineralogical and chemical composition was changed by melting and crystallization processes, they are divided several groups: HED meteorites. They may have originated on the asteroid 4 Vesta, because their reflection spectra are similar, they are named after the initial letters of the three subgroups: Howardites Eucrites Diogenites Angrites Aubrites Lunar meteorites are meteorites that originated from the Moon. Martian meteorites are meteorites, they are divided into three main groups, with two exceptions: Shergottites Nakhlites Chassignites OPX martian meteorites Regolith/Soil samples Glossary of meteoritics Achondrite Images from Meteorites Australia
Cosmic rays are high-energy radiation originating outside the Solar System and from distant galaxies. Upon impact with the Earth's atmosphere, cosmic rays can produce showers of secondary particles that sometimes reach the surface. Composed of high-energy protons and atomic nuclei, they are originated either from the sun or from outside of our solar system. Data from the Fermi Space Telescope have been interpreted as evidence that a significant fraction of primary cosmic rays originate from the supernova explosions of stars. Active galactic nuclei appear to produce cosmic rays, based on observations of neutrinos and gamma rays from blazar TXS 0506+056 in 2018; the term ray is somewhat of a misnomer due to a historical accident, as cosmic rays were at first, wrongly, thought to be electromagnetic radiation. In common scientific usage, high-energy particles with intrinsic mass are known as "cosmic" rays, while photons, which are quanta of electromagnetic radiation are known by their common names, such as gamma rays or X-rays, depending on their photon energy.
In current usage, the term cosmic ray exclusively refers to massive particles – those that have rest mass – as opposed to photons, which have no rest mass, neutrinos, which have negligible rest mass. Massive particles have additional, mass-energy when they are moving, due to relativistic effects. Through this process, some particles acquire tremendously high mass-energies; these are higher than the photon energy of the highest-energy photons detected to date. The energy of the massless photon depends on frequency, not speed, as photons always travel at the same speed. At the higher end of the energy spectrum, relativistic kinetic energy is the main source of the mass-energy of cosmic rays; the highest-energy fermionic cosmic rays detected to date, such as the Oh-My-God particle, had an energy of about 3×1020 eV, while the highest-energy gamma rays to be observed, very-high-energy gamma rays, are photons with energies of up to 1014 eV, the highest energy neutrinos detected so far have energies of several 1015 eV.
Hence, the highest-energy detected fermionic cosmic rays are about 3×106 times as energetic as the highest-energy detected cosmic photons. Of primary cosmic rays, which originate outside of Earth's atmosphere, about 99% are the nuclei of well-known atoms, about 1% are solitary electrons. Of the nuclei, about 90% are simple protons; these fractions vary over the energy range of cosmic rays. A small fraction are stable particles of antimatter, such as positrons or antiprotons; the precise nature of this remaining fraction is an area of active research. An active search from Earth orbit for anti-alpha particles has failed to detect them. Cosmic rays attract great interest due to the damage they inflict on microelectronics and life outside the protection of an atmosphere and magnetic field, scientifically, because the energies of the most energetic ultra-high-energy cosmic rays have been observed to approach 3 × 1020 eV, about 40 million times the energy of particles accelerated by the Large Hadron Collider.
One can show that such enormous energies might be achieved by means of the centrifugal mechanism of acceleration in active galactic nuclei. At 50 J, the highest-energy ultra-high-energy cosmic rays have energies comparable to the kinetic energy of a 90-kilometre-per-hour baseball; as a result of these discoveries, there has been interest in investigating cosmic rays of greater energies. Most cosmic rays, however, do not have such extreme energies. After the discovery of radioactivity by Henri Becquerel in 1896, it was believed that atmospheric electricity, ionization of the air, was caused only by radiation from radioactive elements in the ground or the radioactive gases or isotopes of radon they produce. Measurements of increasing ionization rates at increasing heights above the ground during the decade from 1900 to 1910 could be explained as due to absorption of the ionizing radiation by the intervening air. In 1909, Theodor Wulf developed an electrometer, a device to measure the rate of ion production inside a hermetically sealed container, used it to show higher levels of radiation at the top of the Eiffel Tower than at its base.
However, his paper published in Physikalische Zeitschrift was not accepted. In 1911, Domenico Pacini observed simultaneous variations of the rate of ionization over a lake, over the sea, at a depth of 3 metres from the surface. Pacini concluded from the decrease of radioactivity underwater that a certain part of the ionization must be due to sources other than the radioactivity of the Earth. In 1912, Victor Hess carried three enhanced-accuracy Wulf electrometers to an altitude of 5,300 metres in a free balloon flight, he found the ionization rate increased fourfold over the rate at ground level. Hess ruled out the Sun as the radiation's source by making a balloon ascent during a near-total eclipse. With the moon blocking much of the Sun's visible radiation, Hess still measured rising radiation at rising altitudes, he concluded that "The results of the observations seem most to be explained by the assumption that radiation of high penetrating power enters from above into our atmosphere." In 1913–1914, Werner Kolhörster confirmed Victor Hess's earlier results by measuring the increased ionization enthalpy rate at an altitude of 9 km.
Hess received the Nobel Prize in Physics in 1936