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Asteroids have historically been observed from Earth. The first close-up observation of an asteroid was made by the Galileo spacecraft. Several dedicated missions to asteroids were subsequently launched by NASA and JAXA, with plans for other missions in progress. NASA's NEAR Shoemaker studied Eros, and Dawn observed Vesta and Ceres.
Asteroids as small as 20 metres (66 ft) in diameter can cause significant damage to the local environment and human populations. [5] Larger asteroids penetrate the atmosphere to the surface of the Earth, producing craters if they impact a continent or tsunamis if they impact the sea. Interest in NEOs has increased since the 1980s because of ...
C-type (carbonaceous / ˌ k ɑːr b ə ˈ n eɪ ʃ ə s /) asteroids are the most common variety, forming around 75% of known asteroids. [1] They are volatile-rich and distinguished by a very low albedo because their composition includes a large amount of carbon, in addition to rocks and minerals. They have an average density of about 1.7 g/cm 3.
"We are regularly finding small rocks and small asteroids that are on a path to hit our planet," Pamela Gay, senior scientist at the Planetary Science Institute, said. "But this object is actually ...
The Apollo asteroids are a group of near-Earth asteroids named after 1862 Apollo, discovered by German astronomer Karl Reinmuth in the 1930s. They are Earth-crossing asteroids that have an orbital semi-major axis greater than that of the Earth (a > 1 AU ) but perihelion distances less than the Earth's aphelion distance (q < 1.017 AU).
An asteroid nearly the size of a football field now has roughly a 0.004% chance of hitting Earth in about eight years, NASA says — with the space agency saying it "no longer poses a significant ...
These asteroids, while smaller than the dinosaur killer, struck our planet about 25,000 years apart. They left miles-long craters in the Mid-Atlantic Chesapeake Bay and Siberia: the fourth- and ...
The asteroid Toutatis is listed as a potentially hazardous near-Earth asteroid, yet poses no immediate threat to Earth.(Radar image taken by GDSCC in 1996.)A potentially hazardous object (PHO) is a near-Earth object – either an asteroid or a comet – with an orbit that can make close approaches to the Earth and which is large enough to cause significant regional damage in the event of ...