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.
An asteroid is like a planet, but smaller. The name "asteroid" means "like a star" in the ancient Greek language. Asteroids may look like small stars in the sky, but they really do move around the Sun, while stars only seem to move because the Earth spins. Like planets, asteroids do not make their own light. Because of this, some people think "asteroids" is not a good name, and think that the name "planetoid" ("like a planet") would be a better name.
Most asteroids are made of rock, but some are made of ice or metal. Most asteroids in our Solar System are in the asteroid belt between Mars and Jupiter.
Asteroids are the leftover rock and other material from the formation of the Solar System. These rocks were too small to make a planet, and could not collide to form one.
In the 1600s, Gisuppe Piazzi found the first asteroid. It was named Ceres, and is the biggest object in the asteroid belt. Other asteroids, like Juno, Pallas, and Vesta were found later. Today, astronomers know of hundreds of thousands of asteroids, which range from parts of a mile to 600 miles across.
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Asteroids, sometimes called minor planets or planetoids, are small Solar System bodies in orbit around the Sun, especially in the inner Solar System; they are smaller than planets but larger than meteoroids. The term "asteroid" has historically been applied primarily to minor planets of the inner Solar System, as the outer Solar System was poorly known when it came into common usage. The distinction between asteroids and comets is made on visual appearance: Comets show a perceptible coma while asteroids do not.
The asteroid belt is the region of the Solar System located roughly between the orbits of the planets Mars and Jupiter. It is occupied by numerous irregularly shaped bodies called asteroids or minor planets. The asteroid belt region is also termed the main belt to distinguish it from other concentrations of minor planets within the Solar System, such as the Kuiper belt and scattered disc.
An impact event is the collision of a large meteorite, asteroid, comet, or other celestial object with the Earth or another planet. Impact events have been a plot and background element in science fiction since knowledge of real impacts became established in the scientific mainstream.
Asteroid mitigation strategies are methods by which near-Earth objects could be diverted, preventing potentially catastrophic impact events. A sufficiently large impact would cause massive tsunamis and/or, by placing large quantities of dust into the stratosphere blocking sunlight, an impact winter. A collision between the earth and a ~10 km object 65 million years ago is believed to have produced the Chicxulub Crater and the Cretaceous–Tertiary extinction event.
While in theory the chances of such an event are no greater now than at any other time in history, recent astronomical events (such as Shoemaker-Levy 9) have drawn attention to such a threat, and advances in technology have opened up new options.
Asteroid mining refers to the possibility of exploiting raw materials from asteroids and planetoids in space, especially near-Earth objects. Minerals and volatiles could be mined from an asteroid or spent comet to provide space construction material (e.g., iron, nickel, titanium), or to return to Earth (e.g., platinum and cobalt), to extract water and oxygen to sustain the lives of prospector-astronauts on site, and to extract hydrogen and oxygen for use as rocket fuel. Even a relatively small metalic asteroid with a diameter of 1 mile can contain more than $20 trillion US dollars worth of industrial and precious metals.
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