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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". [43] [44] There are more than 1,100 documented falls listed in widely used databases, [45] [46] [47] most of which have specimens in modern collections.
Typical analyses include investigation of the minerals that make up the meteorite, their relative locations, orientations, and chemical compositions; analysis of isotope ratios; and radiometric dating. These techniques are used to determine the age, formation process, and subsequent history of the material forming the meteorite.
Fall – a meteorite that was seen while it fell to Earth and found. Find – a meteorite that was found without seeing it fall. Fossil meteorite – a meteorite that was 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 Some or all of the original cosmic material has been replaced by diagenetic minerals.
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, [11] [23] [24] creating a streak of light via its rapid motion and sometimes ...
Space weathering is the type of weathering that occurs to any object exposed to the harsh environment of outer space. Bodies without atmospheres (including the Moon , Mercury , the asteroids , comets , and most of the moons of other planets) take on many weathering processes:
A comet is an icy, small Solar System body that warms and begins to release gases when passing close to the Sun, a process called outgassing.This produces an extended, gravitationally unbound atmosphere or coma surrounding the nucleus, and sometimes a tail of gas and dust gas blown out from the coma.
In gaps between the kamacite and taenite lamellae, a fine-grained mixture called plessite is often found. An iron nickel phosphide, schreibersite, is present in most nickel-iron meteorites, as well as an iron-nickel-cobalt carbide, cohenite. Graphite and troilite occur in rounded nodules up to several cm in size. [2]
Because ordinary chondrites represent 80% of the meteorites that fall to earth, and because ordinary chondrites contain 60–80% chondrules, it follows that (excluding dust) most of the meteoritic material that falls on earth is made up of chondrules. Chondrules can range in diameter from just a few micrometers to over 1 centimetre (0.39 in).