Yahoo Web Search

  1. About 55,300,000 search results
  1. Pline l'Ancien , Extrait d’ Histoire Naturelle , livre II , chapitre XXXVIII: De aere ; Quare lapidibus pluat (De l'air: pourquoi il pleut des pierres) L' histoire des représentations des météorites montre l'évolution des différentes perceptions de ces objets au cours des siècles, depuis l'objet sacré jusqu'à l'objet scientifique. Tout au long des siècles, les météorites ont été ...

  2. en.wikipedia.org › wiki › MeteoriteMeteorite - Wikipedia

    • Fall Phenomena
    • Classification
    • Chemistry
    • Weathering
    • Collection
    • in Human Affairs
    • Notable Examples
    • External Links

    Most meteoroids disintegrate when entering the Earth's atmosphere. Usually, 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 typically arrive at the surface at their terminal velocityand, at most, create a small pit. Large meteoroids may strike the earth with a significant fraction of their escape velocity (second cosmic velocity), leaving behind a hypervelocity impact crater. The kind of crater will depend on the size, composition, degree of fragmentation, and 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 easily able to transit the atmosphere intact. Examples of craters caused by iron meteoroids include Barringer Meteor Crater, Odessa Meteor Crater, Wabar craters, and Wolfe Creek cra...

    Most meteorites are stony meteorites, classed as chondrites and achondrites. Only about 6% of meteorites are iron meteorites or a blend of rock and metal, the stony-iron meteorites. Modern classification of meteorites is complex. The review paper of Krot et al. (2007)summarizes modern meteorite taxonomy. About 86% of the meteorites are chondrites, which are named for the small, round particles they contain. These particles, or chondrules, are composed mostly of silicate minerals that appear to have been melted while they were free-floating objects in space. Certain types of chondrites also contain small amounts of organic matter, including amino acids, and presolar grains. Chondrites are typically about 4.55 billion years old and are thought to represent material from the asteroid belt that never coalesced into large bodies. Like comets, chondritic asteroids are some of the oldest and most primitive materials in the Solar System. Chondrites are often considered to be "the building b...

    In March 2015, NASA scientists reported that complex organic compounds found in DNA and RNA, including uracil, cytosine, and thymine, have been formed in the laboratory under outer space conditions, using starting chemicals, such as pyrimidine, found in meteorites. Pyrimidine and polycyclic aromatic hydrocarbons (PAHs) may have been formed in red giants or in interstellar dustand gas clouds, according to the scientists. In January 2018, researchers found that 4.5 billion-year-old meteorites found on Earth contained liquid water along with prebiotic complex organic substances that may be ingredients for life. In November 2019, scientists reported detecting sugar molecules in meteorites for the first time, including ribose, suggesting that chemical processes on asteroids can produce some organic compounds fundamental to life, and supporting the notion of an RNA world prior to a DNA-based origin of lifeon Earth.

    Most meteorites date from the early Solar System and are by far the oldest extant material on Earth. Analysis of terrestrial weatheringdue to water, salt, oxygen, etc. is used to quantify the degree of alteration that a meteorite has experienced. Several qualitative weathering indices have been applied to Antarctic and desertic samples. The most commonly employed weathering scale, used for ordinary chondrites, ranges from W0 (pristine state) to W6(heavy alteration).

    A "meteorite fall", also called an "observed fall", is a meteorite collected after its arrival was observed by people or automated devices. Any other meteorite is called a "meteorite find". There are more than 1,100 documented falls listed in widely used databases, most of which have specimens in modern collections. As of January 2019[update], the Meteoritical Bulletin Databasehad 1,180 confirmed falls.

    Meteorites have figured into human culture since their earliest discovery as ceremonial or religious objects, as the subject of writing about events occurring in the sky and as a source of peril. The oldest known iron artifacts are nine small beads hammered from meteoritic iron. They were found in northern Egypt and have been securely dated to 3200 BC.

    Naming

    Meteorites are always named for the places they were found, where practical, usually 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 (e.g., Allan Hills 84001 or Dimmitt (b)). The name designated by the Meteoritical Societyis used by scientists, catalogers, and most collectors.

    Disintegrating meteoroids

    1. Tunguska event in Siberia1908 (no crater) 2. Vitim eventin Siberia 2002 (no crater) 3. Chelyabinsk eventin Russia 2013 (no known crater)

  3. People also ask

    How big is the Black Beauty meteorite?

    What kind of meteorite is the Muonionalusta meteorite?

    How many meteorites have been found on Mars?

    Which is the oldest meteorite in the world?

  4. Oct 23, 2017 · Français : Météorite Esquel, trouvée en 1951 en Argentine. Météorite mixte (Pallasite). Ce fragment, composé d'un fond de fer, comprend des grains d'olivine. Les scientifiques pensent actuellement (octobre 2017) que cette météorite appartient au groupe des pallasites et qu'elle s'est formée à la suite de la collision entre le noyau de fer d'un astéroïde différencié et le manteau ...

  5. en.wikipedia.org › wiki › MeteoroidMeteoroid - Wikipedia

    A meteor, known colloquially as a shooting star or falling star, is the visible passage of a glowing meteoroid, micrometeoroid, comet or asteroid through Earth's atmosphere, after being heated to incandescence by collisions with air molecules in the upper atmosphere, creating a streak of light via its rapid motion and sometimes also by shedding glowing material in its wake.

  6. A Martian meteorite is a rock that formed on Mars, was ejected from the planet by an impact event, and traversed interplanetary space before landing on Earth as a meteorite. As of September 2020, 277 meteorites had been classified as Martian, less than half a percent of the 72,000 meteorites that have been classified.

    • Description
    • Scientific Investigation
    • Similar Event
    • See Also
    • External Links

    On 30 June 1908 (N. S.) (cited in Russia as 17 June 1908, O. S., before the implementation of the Soviet calendar in 1918), at around 07:17 local time, Evenki natives and Russian settlers in the hills northwest of Lake Baikal observed a bluish light, nearly as bright as the sun, moving across the sky and leaving a thin trail. Closer to the horizon, there was a flash producing a billowing cloud, followed by a pillar of fire that cast a red light on the landscape. The pillar split in two and faded, turning to black. About ten minutes later, there was a sound similar to artillery fire. Eyewitnesses closer to the explosion reported that the source of the sound moved from the east to the north of them. The sounds were accompanied by a shock wavethat knocked people off their feet and broke windows hundreds of kilometres away. The explosion registered at seismic stations across Eurasia, and air waves from the blast were detected in Germany, Denmark, Croatia, and the United Kingdom—and as f...

    Since the 1908 event, there have been an estimated 1,000 scholarly papers (most in Russian) published about the Tunguska explosion. Owing to the remoteness of the site and the limited instrumentation available at the time of the event, modern scientific interpretations of its cause and magnitude have relied chiefly on damage assessments and geological studies conducted many years after the event. Estimates of its energy have ranged from 3–30 megatons of TNT (13–126 petajoules). It was not until more than a decade after the event that any scientific analysis of the region took place, in part due to the isolation of the area and significant political upheaval affecting Russia in the 1910s. In 1921, the Russian mineralogist Leonid Kulik led a team to the Podkamennaya Tunguska River basin to conduct a survey for the Soviet Academy of Sciences. Although they never visited the central blast area, the many local accounts of the event led Kulik to believe that the explosion had been caused...

    A smaller air burst occurred over a populated area on 15 February 2013, at Chelyabinsk in the Ural district of Russia. The exploding meteoroid was determined to have been an asteroid that measured about 17–20 metres (56–66 ft) across. It had an estimated initial mass of 11,000 tonnes and exploded with an energy release of approximately 500 kilotons.The air burst inflicted over 1,200 injuries, mainly from broken glass falling from windows shattered by its shock wave.

    Evgenii A. Vaganov; Malkolm K. Hughes; Pavel P. Silkin; Valery D. Nesvetailo (2004). "The Tunguska Event in 1908: Evidence from Tree-Ring Anatomy" (PDF). Astrobiology. 4 (3): 391–399. Bibcode:2004A...
  1. People also search for