Instruct: Given a question, retrieve documents that can help answer the question.
Query: What was the largest asteroid to ever hit Earth?
Throughout recorded history, hundreds of Earth impacts (and exploding bolides) have been reported, with some occurrences causing deaths, injuries, property damage, or other significant localised consequences.[3] One of the best-known recorded events in modern times was the Tunguska event, which occurred in Siberia, Russia, in 1908. The 2013 Chelyabinsk meteor event is the only known such incident in modern times to result in a large number of injuries, excluding the 1490 Ch'ing-yang event in China. The Chelyabinsk meteor is the largest recorded object to have encountered the Earth since the Tunguska event. The asteroid impact that caused Mistastin crater generated temperatures exceeding 2,370°C, the highest known to have occurred on the surface of the Earth.[4]
 is a member of the Apollo group of asteroids, which are Earth-crossing asteroids. They are the largest group of near-Earth objects with approximately 10 thousand known members. As it just grazes the orbit of Earth, the Minor Planet Center (MPC), groups it to the non-Earth crossing Amor asteroids.
The asteroid that hit Vredefort is estimated to have been one of the largest ever to strike Earth (at least since the Hadean Eon some four billion years ago), thought to have been approximately in diameter. The bolide that created the Sudbury Basin could have been even larger.
, provisional designation , is an asteroid on an eccentric orbit, classified as near-Earth object and potentially hazardous asteroid of the Apollo group, approximately 2.5 kilometers in diameter. It was discovered on 13 November 2002, by astronomers of the Near-Earth Asteroid Tracking program at Palomar Observatory in California, United States. It is one of the largest potentially hazardous asteroid known to exist.
Colonization of asteroids would require space habitats. The asteroid belt has significant overall material available, the largest object being Ceres, although it is thinly distributed as it covers a vast region of space. Unmanned supply craft should be practical with little technological advance, even crossing 500 million kilometers of space. The colonists would have a strong interest in assuring their asteroid did not hit Earth or any other body of significant mass, but would have extreme difficulty in moving an asteroid of any size. The orbits of the Earth and most asteroids are very distant from each other in terms of delta-v and the asteroidal bodies have enormous momentum. Rockets or mass drivers can perhaps be installed on asteroids to direct their path into a safe course.
Until the age of space travel, objects in the asteroid belt were merely pinpricks of light in even the largest telescopes and their shapes and terrain remained a mystery. The best modern ground-based telescopes and the Earth-orbiting Hubble Space Telescope can resolve a small amount of detail on the surfaces of the largest asteroids, but even these mostly remain little more than fuzzy blobs. Limited information about the shapes and compositions of asteroids can be inferred from their light curves (their variation in brightness as they rotate) and their spectral properties, and asteroid sizes can be estimated by timing the lengths of star occulations (when an asteroid passes directly in front of a star). Radar imaging can yield good information about asteroid shapes and orbital and rotational parameters, especially for near-Earth asteroids. In terms of delta-v and propellant requirements, NEOs are more easily accessible than the Moon.[111]
1221 Amor, provisional designation "", is an asteroid and near-Earth object on an eccentric orbit, approximately in diameter. It is the namesake of the Amor asteroids, the second-largest subgroup of near-Earth objects. Discovered by Eugène Delporte at the Uccle Observatory in 1932, it was the first time that an asteroid was seen to approach Earth so closely. The assumed S-type asteroid is one of few asteroids for which no rotation period has been determined. It was named for Cupid, also known as "Amor" in Latin, the Roman equivalent of the Greek god Eros.
 is a member of the dynamical Apollo group, which are Earth-crossing asteroids. Apollo asteroids are the largest subgroup of near-Earth objects.
After Ceres, Asteroid 433 Eros is perhaps the most-commonly mentioned asteroid, probably because it is one of the largest near-Earth asteroids.
is a member of the dynamical Apollo group, which are Earth-crossing asteroids. Apollo asteroids are the largest subgroup of near-Earth objects. Unlike many Apollo asteroids, this asteroid is not a Mars-crosser, as its aphelion is smaller than the orbit of the Red Planet at 1.66 AU.
For asteroids that are actually on track to hit Earth the predicted probability of impact continues to increase as more observations are made. This very similar pattern makes it difficult to differentiate between asteroids which will only come close to Earth and those which will actually hit it. This in turn makes it difficult to decide when to raise an alarm as gaining more certainty takes time, which reduces the time available to react to a predicted impact. However raising the alarm too soon has the danger of causing a false alarm and creating a Boy Who Cried Wolf effect if the asteroid in fact misses Earth.
Of the 262 near-Earth asteroids (NEAs), 47 of them are considered potentially hazardous asteroids (PHAs), a subset of the much larger family of NEOs, but particularly more likely to hit Earth and cause significant destruction. NEOs can be divided into NECs (comets only) and NEAs (asteroids only), and further into subcategories such as Atira or Apohele asteroids, Aten asteroids, Apollo asteroids, Amor asteroids and the potentially hazardous asteroids (PHAs).
Each year, the Earth is hit by diameter meteoroids that deliver an explosion above the surface with the power equivalent of one kiloton TNT. The Earth is hit every day by a meteor less than in diameter, that disintegrates before reaching the surface. The meteors that do make it to the surface tend to strike unpopulated areas, and cause no harm. A human is more likely to die in a fire, flood, or other natural disaster than to die because of an asteroid or comet impact, which is between a 1 in 3,000 and 1 in 250,000 chance. Another study in 1994 found a 1 in 10,000 chance that the Earth will be hit by a large asteroid or comet with a diameter of about during the next century. This object would be capable of disrupting the ecosphere and would kill a large fraction of the world's population. One such object, Asteroid 1950 DA, currently has a 0.005% chance of colliding with Earth in the year 2880, though when first discovered the probability was 0.3%. The probability goes down as orbits are refined with additional measurements.
, provisional designation , is a stony asteroid, slow rotator and suspected tumbler on a highly eccentric orbit, classified as near-Earth object and potentially hazardous asteroid of the Amor and Apollo group, respectively. It was discovered on 31 August 2003, by astronomers of the Near-Earth Asteroid Tracking program at the Haleakala Observatory in Hawaii, United States. The Q-type asteroid has a rotation period of 114.4 hours and possibly an elongated shape. It measures approximately in diameter and belongs the largest potentially hazardous asteroids known to exist.
Eros ( ; minor planet designation: 433 Eros), provisional designation , is a stony and elongated asteroid of the Amor group and the first discovered and second-largest near-Earth object with a mean-diameter of approximately 16.8 kilometers. Visited by the NEAR Shoemaker space probe in 1998, it became the first asteroid ever studied from orbit.
 is a member of the Apollo group of asteroids, which are Earth-crossing asteroids. They are the largest group of near-Earth objects with approximately 10 thousand known members.
The only object that has ever been rated at 4 on the Torino Scale (since downgraded), the Aten asteroid (99942) Apophis, has an Earth MOID of 0.000316 AU. This is not the smallest Earth MOID in the catalogues; many bodies with a small Earth MOID are not classed as PHO's because the objects are less than roughly 140 meters in diameter (or absolute magnitude, "H" < 22). Earth MOID values are generally more practical for asteroids less than 140 meters in diameter as those asteroids are very dim and often have a short observation arc with a poorly determined orbit. The only objects that have been detected and had their Earth-MOID calculated before Earth impact were the small asteroids and 2014 AA. was listed with a MOID of 0.00001 AU in the Minor Planet Center database, and is the smallest MOID calculated for an Apollo asteroid. It is even smaller at the more precise JPL Small Body Database (0.0000078 AU).
Bamberga (minor planet designation: 324 Bamberga) is one of the largest asteroids in the asteroid belt. It was discovered by Johann Palisa on 25 February 1892 in Vienna. It is the 14th-largest asteroid in the asteroid belt. Apart from the near-Earth asteroid Eros, it was the last asteroid which is "ever" easily visible with binoculars to be discovered.
 is a member of the dynamical Apollo group, which are Earth-crossing asteroids. Apollo asteroids are the largest subgroup of near-Earth objects.
It is the largest near-Earth asteroid discovered since 3552 Don Quixote in 1983. On 2007 October 11 the asteroid passed from Earth. It currently makes closer approaches to Mars than it does Earth. The asteroid has a rotation period of 12.05 hours.
For asteroids that are actually on track to hit Earth the predicted probability of impact continues to increase as more observations are made. This very similar pattern makes it difficult to differentiate between asteroids which will only come close to Earth and those which will actually hit it. This in turn makes it difficult to decide when to raise an alarm as gaining more certainty takes time, which reduces the time available to react to a predicted impact. However raising the alarm too soon has the danger of causing a false alarm and creating a Boy Who Cried Wolf effect if the asteroid in fact misses Earth.
Asteroid capture Asteroid impact avoidance– Methods to prevent destructive asteroid hits B612 Foundation Earth Impact Database Global catastrophic risk– Hypothetical future event that has the potential to damage human well-being on a global scale Impact gardening Late Heavy Bombardment– Interval when a disproportionately large number of asteroids are theorised to have collided with the inner planets List of bolides List of impact craters on Earth List of meteor air bursts List of unconfirmed impact craters on Earth Near-Earth asteroids Near-Earth object Near-Earth Object Camera Palermo Technical Impact Hazard Scale Pan-STARRS Potentially hazardous object Spaceguard– Efforts to discover, catalogue, and study asteroids that might impact Earth Torino scale, 0 to 10
 is an Aten asteroid. It passed 43,000 km from the Earth on 18 March 2004. For comparison, geostationary satellites orbit Earth at 35,790 kilometers. Despite its small size, it is still the fourth largest asteroid detected coming closer to the Earth than the Moon. 
The classic space mission is the Earth-colliding asteroid interception mission. Using nuclear detonations to split or deflect the asteroid is risky at best. Such a tactic could actually make the problem worse by increasing the amount of asteroid fragments that do end up hitting the Earth. Robert Zubrin writes:
More than 1M asteroids have the potential to impact Earth and through all the available telescopes worldwide, we have discovered only about one percent. The 100X Declaration calls for increasing the asteroid discovery rate to 100,000 (or 100x) per year within the next 10 years. “The more we learn about asteroid impacts, the clearer it became that the human race has been living on borrowed time,” remarked Brian May. “Asteroid Day and the 100X Declaration are ways for the public to contribute to an awareness of the Earth’s vulnerability and the realization that Asteroids hit Earth all the time.” Asteroid Day would the vehicle to garner public support to increase our knowledge of when asteroids might strike and how we can protect ourselves.”