Blog
Save
Email
Print
ShareNear-Earth asteroids (NEAs) are asteroids whose orbits are close to Earth's orbit.
Some NEAs' orbits intersect Earth's so they pose a collision danger.
On the other hand, NEAs are most easily accessible for spacecraft from Earth; in fact, some can be reached with much less delta-v than it takes to reach the Moon.
Two NEAs have been visited by spacecraft: 433 Eros, by NASA's Near Earth Asteroid Rendezvous probe, and 25143 Itokawa, by the JAXA Hayabusa mission. Roughly 1000 near-Earth asteroids are known, ranging in size up to approximately 32 kilometres (1036 Ganymed).
Tens of thousands probably exist, with estimates placing the number of NEAs larger than one kilometer in diameter at up to 2,000. NEAs only survive in their orbits for 10 million to 100 million years.
They are eventually eliminated by orbital decay and accretion by the Sun, collisions with the inner planets, or by being ejected from the solar system by near misses with the planets.
Such processes should have eliminated them all long ago, so it is assumed they are resupplied on a regular basis by orbital migration of objects from the asteroid belt.
For more information about the topic Near-Earth asteroid, read the full article at Wikipedia.org, or see the following related articles:
Asteroid belt — The asteroid belt is a region of the solar system falling roughly between the planets Mars and Jupiter where the greatest concentration of asteroid ... > read more
Near-Earth object — Near-Earth objects (NEO) are asteroids, comets and large meteoroids whose orbit intersects Earth's orbit and which may therefore pose a collision ... > read more
Neptune's natural satellites — Neptune has 13 known moons. The largest by far is Triton, discovered by William Lassell just 17 days after the discovery of Neptune itself. It took a ... > read more
Dysnomia (moon of Eris) — Dysnomia, is a moon of the dwarf planet Eris. The satellite is about 60 times fainter than Eris, and its diameter is estimated to be approximately ... > read more
Torino Scale — The Torino Scale is a method for categorizing the impact hazard associated with near-Earth objects (NEOs) such as asteroids and ... > read more
Deimos (moon) — Deimos is probably an asteroid that was perturbed by Jupiter into an orbit that allowed it to be captured by Mars, though this hypothesis is still in ... > read more
Asteroid — Asteroids, also called minor planets or planetoids, are a class of astronomical object. The term asteroid is generally used to indicate a diverse ... > read more
Phobos (moon) — Phobos is the larger and innermost of Mars' two moons, and is named after Phobos, son of Ares (Mars) from Greek Mythology. Phobos orbits closer to a ... > read moreRecommend this page on Facebook, Twitter,
and Google +1:
Other bookmarking and sharing tools:
more 