Enstatite chondrites are a rare form of meteorite thought to comprise only about 2% of the chondrites that fall on Earth. Only about 200 E-Type chondrites are known. E-type chondrites are among the most chemically reduced rocks known, with most of their iron taking the form of metal or sulfide rather than an oxide, they tend to be high in the mineral enstatite. Based on spectral analysis, it has been suggested that the asteroid 16 Psyche may be the common parent for this type of meteorite. Unlike most other chondrites, the minerals in enstatite chondrites contain no iron oxide, they are the driest objects in the solar system, consisting of only 0.01% water. Metallic Fe-Ni and Fe-bearing sulfide minerals contain nearly all of the iron in this type of meteorite. Enstatite chondrites contain a variety of unusual minerals that can only form in reducing conditions, including oldhamite, niningerite and alkali sulfides. All enstatite chondrites are dominantly composed of enstatite-rich chondrules plus abundant grains of metal and sulfide minerals.
Dusty matrix material is uncommon and refractory inclusions are rare. Chemically, enstatite chondrites are low in refractory lithophile elements, their oxygen isotopic compositions are intermediate between ordinary and carbonaceous chondrites, are similar to rocks found on the Earth and Moon. Their lack of oxygen content may mean that they were formed near the center of the solar nebula that created the solar system within the orbit of Mercury. Most enstatite chondrites have experienced thermal metamorphism on the parent asteroids, they are divided into two groups: EH chondrites contain small chondrules and high ratios of siderophile elements to silicon. Somewhat more than 10% of the rock is composed of metal grains. A diagnostic feature of EH chondrites is. EL chondrites contain larger chondrules, low ratios of siderophile elements to silicon. Fe-Ni metal contains ~1 wt% Silicon; the largest known recorded E-type chondrite fall happened in the town of Abee, in Alberta in 1952. The 107 kilograms stone fell in a farmer's wheat field, creating an impact pit 0.7 m in diameter and 1.5 m deep.
Based on estimates of its velocity and inclination, it is thought to have arrived on a low-speed, low-inclination orbit that had a perihelion near 0.95 AU and an aphelion close to 2.74 AU. It is classified as being a shock-melted breccia, its minerals having recrystallized after the impact that knocked it off of its parent body; the meteorite was acquired by the Geological Survey of Canada, a large sample of it is on display at the Royal Ontario Museum. The largest known E-type chondrite in the asteroid belt may be 21 Lutetia, with a diameter of 100 kilometres, based on observations from the Rosetta spacecraft, ESO's New Technology Telescope, NASA Infrared Telescope Facility, the Spitzer Space Telescope. Glossary of meteoritics Chondrite Meteorite
Arkansas is a state in the southern region of the United States, home to over 3 million people as of 2018. Its name is of Siouan derivation from the language of the Osage denoting their related kin, the Quapaw Indians; the state's diverse geography ranges from the mountainous regions of the Ozark and the Ouachita Mountains, which make up the U. S. Interior Highlands, to the densely forested land in the south known as the Arkansas Timberlands, to the eastern lowlands along the Mississippi River and the Arkansas Delta. Arkansas is the 33rd most populous of the 50 United States; the capital and most populous city is Little Rock, located in the central portion of the state, a hub for transportation, business and government. The northwestern corner of the state, such as the Fayetteville–Springdale–Rogers Metropolitan Area and Fort Smith metropolitan area, is a population and economic center; the largest city in the state's eastern part is Jonesboro. The largest city in the state's southeastern part is Pine Bluff.
The Territory of Arkansas was admitted to the Union as the 25th state on June 15, 1836. In 1861, Arkansas withdrew from the United States and joined the Confederate States of America during the Civil War. On returning to the Union in 1868, the state continued to suffer due to its earlier reliance on slavery and the plantation economy, causing the state to fall behind economically and socially. White rural interests continued to dominate the state's politics until the civil rights movement. Arkansas began to diversify its economy following World War II and relies on its service industry, poultry, tourism and rice; the culture of Arkansas is observable in museums, novels, television shows and athletic venues across the state. People such as politician and educational advocate William Fulbright; the name Arkansas was applied to the Arkansas River and derives from a French term, the plural term for Quapaws, a Dhegiha Siouan-speaking Native American people who settled in Arkansas around the 13th century.
This comes from an Algonquian term, /akansa/, for the Quapaws, is also the root term for Kansas. The name has been spelled in a variety of fashions. In 1881, the pronunciation of Arkansas with the final "s" being silent was made official by an act of the state legislature after a dispute arose between Arkansas's two U. S. senators as one favored the pronunciation as AR-kən-saw while the other favored ar-KAN-zəs. In 2007, the state legislature passed a non-binding resolution declaring that the possessive form of the state's name is Arkansas's, followed by the state government. Arkansas borders Louisiana to the south, Texas to the southwest, Oklahoma to the west, Missouri to the north, Tennessee and Mississippi to the east; the United States Census Bureau classifies Arkansas as a southern state, sub-categorized among the West South Central States. The Mississippi River forms most of Arkansas's eastern border, except in Clay and Greene, counties where the St. Francis River forms the western boundary of the Missouri Bootheel, in many places where the channel of the Mississippi has meandered from its original 1836 course.
Arkansas can be split into two halves, the highlands in the northwest half and the lowlands of the southeastern half. The highlands are part of the Southern Interior Highlands, including The Ozarks and the Ouachita Mountains; the southern lowlands include the Arkansas Delta. This dual split can yield to general regions named northwest, northeast, southeast, or central Arkansas; these directionally named regions are broad and not defined along county lines. Arkansas has seven distinct natural regions: the Ozark Mountains, Ouachita Mountains, Arkansas River Valley, Gulf Coastal Plain, Crowley's Ridge, the Arkansas Delta, with Central Arkansas sometimes included as a blend of multiple regions; the southeastern part of Arkansas along the Mississippi Alluvial Plain is sometimes called the Arkansas Delta. This region is a flat landscape of rich alluvial soils formed by repeated flooding of the adjacent Mississippi. Farther away from the river, in the southeast portion of the state, the Grand Prairie consists of a more undulating landscape.
Both are fertile agricultural areas. The Delta region is bisected by a geological formation known as Crowley's Ridge. A narrow band of rolling hills, Crowley's Ridge rises from 250 to 500 feet above the surrounding alluvial plain and underlies many of the major towns of eastern Arkansas. Northwest Arkansas is part of the Ozark Plateau including the Ozark Mountains, to the south are the Ouachita Mountains, these regions are divided by the Arkansas River; these mountain ranges are part of the U. S. Interior Highlands region, the only major mountainous region between the Rocky Mountains and the Appalachian Mountains; the highest point in the state is Mount Magazine in the Ouachita Mountains, which rises to 2,753 feet above sea level. Arkansas has many rivers and reservoirs within or along its borders. Major tributaries of the Mississippi River include the Arkansas River, the White River, the St. Francis River; the Arkansas is fed by the Mulberry River and the Fou
Lodranites are a small group of primitive achondrite meteorites that consists of meteoric iron and silicate minerals. Olivine and pyroxene make up most of the silicate minerals. Like all primitive achondrites lodranites share similarities with achondrites; the lodranite group is named after Lodhran, where the type specimen fell on 1 October 1868 at 14:00. Eyewitnesses of the fall reported a loud bang accompanied by a rising dust cloud to the east of the city, which led to the discovery and retrieval of the meteorite; the "meteorite from Lodran" was first described by Gustav Tschermak in 1870. He described the meteorite being "apart from the nickel-iron it is an olivine-bronzite aggregates of such outstanding sort, that has never been found in a meteorite before only similar to the terrestrial olivine rock". George Thurland Prior was the first to classify the lodran meteorite as the only member of the lodranite group, he saw close similarities to the ureilites. Lodranites are primitve achondrites.
They are coarser grained than acapulcoites. The main mineral phases are low calcium pyroxene and olivine with minor amounts of plagioclase and troilite; because of their composition they are related to H class chondrites. Lodranites can be described as chondrites that were heated to the point where FeNi and FeS reach an eutectic point. At this point partial melting occurred and some of the metal- and silica melt was removed; the Lodran meteorite is described as having equal amounts of metal and pyroxene which make up most of the volume. Other minerals include sulphide, chromite and chrome-diopside; the lodranites and acapulcoites share the same parent body, similar to an S-type asteroid. The lodranites are coarser grained and yield higher temperatures with isotopic methods and are therefore thought to be from greater depths within the parent body; the cooling path of the parent body can be reconstructed by using radiometric dating. The Hf-W system in high-Ca pyroxenes has a closing temperature in between 975 and 1025 °C.
The parent body cooled under this temperature between 4562.6 million years ago. This means. Trace elements indicate that the parent body had a complex geologic history with partial melting, melt migration and metasomatism. Glossary of meteoritics
IAB meteorites are a group of iron meteorites according to their overall composition and a group of primitive achondrites because of silicate inclusions that show a strong affinity to winonaites and chondrites. The IAB meteorites are composed of meteoric silicate inclusions. Structurally they can be hexahedrites, fine to coarse octahedrites, or ataxites. Most of them are octahedrite with medium to coarse taenite-lamella and distinct Widmanstätten patterning; the silicate inclusions are composed of low-Ca pyroxene, high-Ca pyroxene, plagioclase, graphite, different phosphates, meteoric iron and traces of daubréelite and chromite. This composition is similar to the composition of winonaites and it is therefore argued that the two groups share the same parent body. There are similarities with the IIICD meteorites, but it is not yet clear if they are part of that parent body; the IAB group was created from IB groups. Some authors prefer to call it IAB complex. There are numerous subdivisions of the IAB group: Most scientist believe that the winonaites, the IAB meteorites share the same parent body.
It is not yet understood if the IIICD meteorites belong to that body. Canyon Diablo Pitts meteorite Udei station meteorite Goose Lake Meteorite Nantan meteorite Glossary of meteoritics
Field Museum of Natural History
The Field Museum of Natural History known as The Field Museum, is a natural history museum in Chicago, is one of the largest such museums in the world. The museum maintains its status as a premier natural-history museum through the size and quality of its educational and scientific programs, as well as due to its extensive scientific-specimen and artifact collections; the diverse, high-quality permanent exhibitions, which attract up to two million visitors annually, range from the earliest fossils to past and current cultures from around the world to interactive programming demonstrating today's urgent conservation needs. The museum is named in honor of its first major benefactor, the department-store magnate Marshall Field; the museum and its collections originated from the 1893 World’s Columbian Exposition and the artifacts displayed at the fair. The museum maintains a temporary exhibition program of traveling shows as well as in-house produced topical exhibitions; the professional staff maintains collections of over 24 million specimens and objects that provide the basis for the museum’s scientific-research programs.
These collections include the full range of existing biodiversity, meteorites and rich anthropological collections and cultural artifacts from around the globe. The museum's library, which contains over 275,000 books and photo archives focused on biological systematics, evolutionary biology, archaeology and material culture, supports the museum’s academic-research faculty and exhibit development; the academic faculty and scientific staff engage in field expeditions, in biodiversity and cultural research on every continent, in local and foreign student training, in stewardship of the rich specimen and artifact collections. They work in close collaboration with public programming exhibitions and education initiatives; the Field Museum and its collections originated from the 1893 World’s Columbian Exposition and the artifacts displayed at the fair. In order to house for future generations the exhibits and collections assembled for the Exposition, Edward Ayer convinced the merchant Marshall Field to fund the establishment of a museum.
Titled the Columbian Museum of Chicago in honor of its origins, the Field Museum was incorporated by the State of Illinois on September 16, 1893, for the purpose of the "accumulation and dissemination of knowledge, the preservation and exhibition of artifacts illustrating art, archaeology and history." The Columbian Museum of Chicago occupied the only building remaining from the World's Columbian Exposition in Jackson Park, the Palace of Fine Arts. It is now home to the Chicago Museum of Industry. In 1905, the museum's name was changed to the Field Museum of Natural History to honor its first major benefactor and to reflect its focus on the natural sciences. During the period from 1943 to 1966, the museum was known as the Chicago Natural History Museum. In 1921, the Museum moved from its original location in Jackson Park to its present site on Chicago Park District property near downtown. By the late 1930s the Field had emerged as one of the three premier museums in the United States, the other two being the American Museum of Natural History in New York and the National Museum of Natural History at the Smithsonian Institution in Washington DC.
The museum has maintained its reputation through continuous growth, expanding the scope of collections and its scientific research output, in addition to the its award-winning exhibitions, outreach publications, programs. The Field Museum is part of Chicago’s lakefront Museum Campus that includes the John G. Shedd Aquarium and the Adler Planetarium. In 2015, it was reported that an employee had defrauded the museum of $900,000 over a seven-year period to 2014. Animal exhibitions and dioramas such as Nature Walk, Mammals of Asia, Mammals of Africa that allow visitors an up-close look at the diverse habitats that animals inhabit. Most notably featured are the infamous man-eating lions of Tsavo. Evolving Planet follows the evolution of life on Earth over 4 billion years; the exhibit showcases fossils of single-celled organisms, Permian synapsids, extinct mammals, early hominoids. The Field Museum's non-mammalian synapsid collection consists of over 1100 catalogued specimens, including 46 holotypes.
The collection of basal synapsids includes 29 holotypes of caseid, edaphosaurid and sphenacodontid species - 88% of catalogued specimens. Inside Ancient Egypt offers a glimpse into. Twenty-three human mummies are on display as well as many mummified animals; the exhibit features a three-story replica of the mastaba tomb of the son of Unas. Displayed are: an ancient marketplace showing artifacts of everyday life, a shrine to the cat goddess Bastet, dioramas showing the afterlife preparation process for the dead; the Ancient Americas displays 13,000 years of human ingenuity and achievement in the Western Hemisphere, where hundreds of diverse societies thrived long before the arrival of Europeans. In this large permanent exhibition visitors can learn the epic story of the peopling of these continents, from the Arctic to the tip of South America. Cultural exhibitions include sections on Tibet and China, where visitors can view traditional clothing. There is an exhibit on life in Africa, where visitors can learn about the many different cultures on the continent, an exhibit where visitors may "visit" several Pacific Islands.
The museum houses an authentic 19th century Māori Meeting House, Ruatepupuke II, from Tokomaru Bay, New Zealand. The Grainger Hall of Gems and its large collection o
HED meteorites are a clan of achondrite meteorites. HED stands for "howardite–eucrite–diogenite"; these achondrites came from a differentiated parent body and experienced extensive igneous processing not much different from the magmatic rocks found on Earth and for this reason they resemble terrestrial igneous rocks. HED meteorites are broadly divided into: Howardites Eucrites DiogenitesSeveral subgroups of both eucrites and diogenites have been found; the HED meteorites account for about 5% of all falls, about 60% of all achondrites. These are all thought to have originated from the crust of the asteroid Vesta, their differences being due to different geologic histories of the parent rock, their crystallization ages have been determined to be between 4.43 and 4.55 billion years from radioisotope ratios. HED meteorites are differentiated meteorites, which were created by igneous processes in the crust of their parent asteroid, it is thought that the method of transport from Vesta to Earth is as follows: An impact on Vesta ejected debris, creating small V-type asteroids.
Either the asteroidal chunks were formed from smaller debris. Some of these small asteroids formed the Vesta family; this event is thought to have happened less than 1 billion years ago. There is an enormous impact crater on Vesta covering much of the southern hemisphere, the best candidate for the site of this impact; the amount of rock, excavated there is many times more than enough to account for all known V-type asteroids. Some of the more far-flung asteroid debris ended up in the 3:1 Kirkwood gap; this is an unstable region due to strong perturbations by Jupiter, asteroids which end up here get ejected onto far different orbits on a timescale of about 100 million years. Some of these bodies are perturbed into near-Earth orbits forming the small V-type near-Earth asteroids such as e.g. 3551 Verenia, 3908 Nyx, or 4055 Magellan. Smaller impacts on these near-Earth objects dislodged rock-sized meteorites, some of which struck Earth. On the basis of cosmic ray exposure measurements, it is thought that most HED meteorites arose from several distinct impact events of this kind, spent from about 6 million to 73 million years in space before striking the Earth.
Glossary of meteoritics Meteorite articles, including discussions of HEDs, in Planetary Science Research Discoveries
The ordinary chondrites are a class of stony chondritic meteorites. They comprise about 87 % of all finds. Hence, they have been dubbed "ordinary"; the ordinary chondrites are thought to have originated from three parent asteroids, with the fragments making up the H chondrite, L chondrite and LL chondrite groups respectively. It is suspected that they are not representative of typical asteroid parent bodies, but rather of a select few which are advantageously placed to send impact fragments to Earth-crossing orbits; such positions secular resonances in the main asteroid belt. In fact, only the one rather insignificant asteroid 3628 Božněmcová has been identified to have a spectrum close to the ordinary chondrites. A probable parent body of the H chondrites is 6 Hebe, but its spectrum is dissimilar due to what is a metal impact melt component, it is that the ordinary chondrites comprise a detailed sample of but a few select asteroids which happen to have been in the right place at the right time to send many fragments toward Earth at the present moment in solar system history.
On the other hand, observations of 243 Ida by the Galileo spacecraft found weathering of Ida's surface, the reflection spectra of freshly exposed parts of the surface resembled that of OC meteorites, while the older regions matched the spectra of common S-type asteroids. The ordinary chondrites comprise three mineralogically and chemically distinct groupings, they differ in the amount of total iron, of iron metal and iron oxide in the silicates: The H chondrites have the Highest total iron, high metal, but lower iron oxide in the silicates The L chondrites have Lower total iron, lower metal, but higher iron oxide in the silicates The LL chondrites have Low total iron and Low metal, but the highest iron oxide content in the silicates. Glossary of meteoritics Chondrite Chondrule The Catalogue of Meteorites A Pictorial of Ordinary Chondrites - Meteorites Australia Gallery of Ordinary Chondrites by James St. John, a geologist at Ohio State University