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Asteroid capture is an orbital insertion of an asteroid around a larger planetary body. When asteroids, small rocky bodies in space, are captured, they become natural satellites , [ 1 ] [ failed verification – see discussion ] specifically either an irregular moon if permanently captured, or a temporary satellite .
The surface of the asteroid appears completely covered in ice. As this ice layer is sublimating, it may be getting replenished by a reservoir of ice under the surface. Organic compounds were also detected on the surface. [98] [99] [97] [100] The presence of ice on 24 Themis makes the initial theory plausible. [97]
Note that this definition includes elements that are not traditionally considered metallic by chemical convention. micrometeorite A very small meteorite that has survived its passage through the atmosphere to reach the surface of a planet or moon, usually ranging in size from 50 μm to 2 mm. Micrometeorites are a major component of cosmic dust.
An asteroid nearly the size of a football field now has roughly a 0.28% chance of hitting Earth in about eight years, NASA says — though at one point earlier its estimate reached as high as 3.1% ...
While the size of a very small fraction of these asteroids is known to better than 1%, from radar observations, from images of the asteroid surface, or from stellar occultations, the diameter of the vast majority of near-Earth asteroids has only been estimated on the basis of their brightness and a representative asteroid surface reflectivity ...
The asteroid is a rare example of an "imminent impactor" -- meaning it was discovered only hours before it entered our atmosphere.
For accretion to occur, impact velocities must be less than about twice the escape velocity, which is about 140 m/s (460 ft/s) for a 100 km (60 mi) radius asteroid. [35] Simple models for accretion in the asteroid belt generally assume micrometer-sized dust grains sticking together and settling to the midplane of the nebula to form a dense ...
A new analysis of this debris has resolved a long debate about the nature of the asteroid, showing that it was a type that originated beyond Jupiter in the outer solar system.