Definitions
Meteoroid: A meteoroid is a sand-to-boulder sized particle of debris in the Solar System. The visible path of a meteoroid that enters Earth's (or another body's) atmosphere is called a meteor. If a meteoroid reaches the ground and survives impact, then it is called a meteorite.
Asteroid: Asteroids, sometimes called minor planets or planetoids, are small Solar System bodies in orbit around the Sun or planets, especially in the inner Solar System; they are smaller than planets but larger than meteoroids.
Meteorite: A meteoroid or a part of it that enters Earth's (or another body's) atmosphere and reaches the ground and survives impact.
Meteor: The visible streak of light that occurs when a meteoroid enters the Earth's atmosphere, known popularly as a shooting star or falling star.
Comet: A small solar system body bigger than a meteoroid that, when close enough to the Sun, exhibits a visible coma, and sometimes a tail, both because of the effects of solar radiation upon the comet's nucleus. Comet nuclei are themselves loose collections of ice, dust and small rocky particles.
- Wikipedia
Basics
A meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids. When it enters the atmosphere, impact pressure causes the body to heat up and emit light, thus forming a fireball, also known as a meteor or shooting/falling star. The term bolide refers to either an extraterrestrial body that collides with the Earth, or to an exceptionally bright, fireball-like meteor regardless of whether it ultimately impacts the surface.
Meteorites have traditionally been divided into three broad categories: stony meteorites are rocks, mainly composed of silicate minerals; iron meteorites are largely composed of metallic iron-nickel; and, stony-iron meteorites contain large amounts of both metallic and rocky material. Modern classification schemes divide meteorites into groups according to their structure, chemical and isotopic composition and mineralogy. See meteorites classification.
Topics of Interest
Meteorite falls are those meteorites that were witnessed by people or automated devices as they moved through the atmosphere or hit the Earth, and were subsequently collected. As of November 2009, there are about 1,083 documented falls that are listed in widely used databases, most of which have specimens in modern collections.
The ultimate goal of meteorite classification is to group together all meteorite specimens that share a common origin on a single, identifiable parent body. This could be a planet, asteroid, Moon, or other current Solar System object, or one that existed some time in the past (e.g. a shattered asteroid). However, with a few exceptions, this goal is beyond the reach of current science, mostly because there is inadequate information about the nature of most solar system bodies (especially asteroids and comets) to achieve such a classification. Instead, modern meteorite classification relies on placing specimens into "groups" in which all members share certain key physical, chemical, isotopic, and mineralogical properties that are consistent with a common origin on a single parent body, even if that body is not identified. It is possible that several meteorite groups classified in this way may come from a single, heterogeneous parent body or that a single group may contain members that came from a variety of very similar but distinct parent bodies. As such information comes to light, the classification system will most likely evolve.
A Mars meteorite is a meteorite that has landed on Earth and originated from Mars. This could have been the result of an impact of a celestial body on Mars, sending material from Mars into space. Of the many thousand meteorites that have been found on Earth, only 34 have been identified as originating from Mars, most of which have been found since 2000.
The Murchison meteorite is named after Murchison, Victoria, in Australia. It is one of the most studied meteorites due to its large mass (>100 kg), the fact that it was an observed fall, and it belongs to a group of meteorites rich in organic compounds.
Iron meteorites consist overwhelmingly of nickel-iron alloys. The metal taken from these meteorites is known as meteoric iron and was one of the earliest sources of usable iron available to man.
The Tunguska Event, or Tunguska explosion, was a powerful explosion that occurred near the Podkamennaya (Lower Stony) Tunguska River in what is now Krasnoyarsk Krai of Russia, at 0 hours 13 minutes 35 seconds Greenwich Mean Time (around 7:14 a.m. local time) on June 30, 1908 (June 17 in the Julian calendar, in use locally at the time).
Although the cause of the explosion is the subject of debate, it is commonly believed to have been caused by the air burst of a large meteoroid or comet fragment at an altitude of 5–10 kilometres (3.1–6.2 mi) above the Earth's surface. Different studies have yielded varying estimates of the object's size, with general agreement that it was a few tens of metres across.
Baetylus or Bethel is a Semitic word denoting a sacred stone, which was supposedly endowed with life. These objects of worship were meteorites, which were dedicated to the gods or revered as symbols of the gods themselves The best known such object is the Black Stone in Mecca, and another one is mentioned as Bethel in Genesis 28:11-19.
Source: Wikipedia (All text is available under the terms of the GNU Free Documentation License and Creative Commons Attribution-ShareAlike License.)
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