An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere.
A near-Earth object (NEO) is any small Solar System body whose orbit brings it into proximity with Earth. By convention, a Solar System body is a NEO if its closest approach to the Sun (perihelion) is less than 1.3 astronomical units (AU). If a NEO's orbit crosses the Earth's orbit, and the object is larger than 140 meters (460 ft) across, it is considered a potentially hazardous object (PHO). Most known PHOs and NEOs are asteroids, but a small fraction are comets.
An impact event is a collision between astronomical objects causing measurable effects. Impact events have physical consequences and have been found to regularly occur in planetary systems, though the most frequent involve asteroids, comets or meteoroids and have minimal effect. When large objects impact terrestrial planets such as the Earth, there can be significant physical and biospheric consequences, though atmospheres mitigate many surface impacts through atmospheric entry. Impact craters and structures are dominant landforms on many of the Solar System's solid objects and present the strongest empirical evidence for their frequency and scale.
Nuclear pulse propulsion or external pulsed plasma propulsion is a hypothetical method of spacecraft propulsion that uses nuclear explosions for thrust. It originated as Project Orion with support from DARPA, after a suggestion by Stanislaw Ulam in 1947. Newer designs using inertial confinement fusion have been the baseline for most later designs, including Project Daedalus and Project Longshot.
Asteroid impact avoidance comprises the methods by which near-Earth objects (NEO) on a potential collision course with Earth could be diverted away, preventing destructive impact events. An impact by a sufficiently large asteroid or other NEOs would cause, depending on its impact location, massive tsunamis or multiple firestorms, and an impact winter caused by the sunlight-blocking effect of large quantities of pulverized rock dust and other debris placed into the stratosphere. A collision 66 million years ago between the Earth and an object approximately 10 kilometres wide is thought to have produced the Chicxulub crater and triggered the Cretaceous–Paleogene extinction event that is understood by the scientific community to have caused the extinction of all non-avian dinosaurs.
A lander is a spacecraft that descends towards, comes to rest on, the surface of an astronomical body. In contrast to an impact probe, which makes a hard landing that damages or destroys the probe upon reaching the surface, a lander makes a soft landing after which the probe remains functional.
Project Orion was a study conducted between the 1950s and 1960s by the United States Air Force, DARPA, and NASA for the purpose of identifying the efficacy of a starship directly propelled by a series of explosions of atomic bombs behind the craft—nuclear pulse propulsion. Early versions of this vehicle were proposed to take off from the ground; later versions were presented for use only in space. Six non-nuclear tests were conducted using models. The project was eventually abandoned for multiple reasons, including the Partial Test Ban Treaty, which banned nuclear explosions in space, and concerns over nuclear fallout.
The B612 Foundation is a private nonprofit foundation headquartered in Mill Valley, California, United States, dedicated to planetary science and planetary defense against asteroids and other near-Earth object (NEO) impacts. It is led mainly by scientists, former astronauts and engineers from the Institute for Advanced Study, Southwest Research Institute, Stanford University, NASA and the space industry.
1566 Icarus is a large near-Earth object of the Apollo group and the lowest numbered potentially hazardous asteroid. It has is an extremely eccentric orbit (0.83) and measures approximately 1.4 km (0.87 mi) in diameter. In 1968, it became the first asteroid ever observed by radar. Its orbit brings it closer to the Sun than Mercury and further out than the orbit of Mars, which also makes it a Mercury-, Venus-, and Mars-crossing asteroid. This stony asteroid and relatively fast rotator with a period of 2.27 hours was discovered on 27 June 1949, by German astronomer Walter Baade at the Palomar Observatory in California. It was named after the mythological Icarus.
Meteor is a 1979 science fiction disaster film directed by Ronald Neame, and starring Sean Connery and Natalie Wood. The film's premise, which follows a group of scientists struggling with Cold War politics after an asteroid is detected to be on a collision course with Earth, was inspired by a 1967 MIT report Project Icarus. The screenplay was written by Oscar winner Edmund H. North and Stanley Mann.
2000 SG344 is a small Aten asteroid first observed in 2000. It is assumed to have a diameter of approximately 37 meters (120 feet) – or roughly twice that of the Chelyabinsk meteor – and an assumed mass of 7.1×107 kg (71,000 tonnes). But the size is only known within about a factor 2. It is the largest object known to have a better than 1/1000 chance (0.1%) of impacting Earth and has the fourth highest cumulative Palermo rating at −2.79. The next good chance to observe the object will be in May 2028 when it passes 0.02 AU (3,000,000 km; 1,900,000 mi) from Earth.
Don Quijote is a past space probe concept that has been studied by the European Space Agency, and which would investigate the effects of crashing a spacecraft into an asteroid to test whether a spacecraft could successfully deflect an asteroid on a collision course with Earth. The orbiter was designed to last for seven years. The mission did not proceed beyond initial studies, currently ESA is working on Asteroid Impact and Deflection Assessment mission as a part of its NEO space mission studies.
The Astrogeology Science Center is the entity within the United States Geological Survey concerned with the study of planetary geology and planetary cartography. It is housed in the Shoemaker Building in Flagstaff, Arizona. The Center was established in 1963 by Eugene Merle Shoemaker to provide lunar geologic mapping and to assist in training astronauts destined for the Moon as part of the Apollo program.
101955 Bennu (provisional designation 1999 RQ36) is a carbonaceous asteroid in the Apollo group discovered by the LINEAR Project on 11 September 1999. It is a potentially hazardous object that is listed on the Sentry Risk Table and has the highest cumulative rating on the Palermo Technical Impact Hazard Scale. It has a cumulative 1-in-1,800 chance of impacting Earth between 2178 and 2290 with the greatest risk being on 24 September 2182. It is named after the Bennu, the ancient Egyptian mythological bird associated with the Sun, creation, and rebirth.
The Asteroid Terrestrial-impact Last Alert System (ATLAS) is a robotic astronomical survey and early warning system optimized for detecting smaller near-Earth objects a few weeks to days before they impact Earth.
Asteroid laser ablation is a proposed method for deflecting asteroids, involving the use of a laser array to alter the orbit of an asteroid. Laser ablation works by heating up a substance enough to allow gaseous material to eject, either through sublimation or vaporization. For most asteroids this process occurs between temperatures in the range of 2,700–3,000 K. The ejecting material creates a thrust, which over an extended period of time can change the trajectory of the asteroid. As a proof of concept on a small scale, Travis Brashears, a researcher at UC Santa Barbara's Experimental Cosmology Lab, led by Dr. Philip Lubin, has already experimentally verified that laser ablation can de-spin and spin-up an asteroid. Further testing and development of this method are being done by groups at UC Santa Barbara, NASA and the University of Strathclyde.
Hyper-velocity Asteroid Mitigation Mission for Emergency Response (HAMMER) is a concept study by NASA on a spacecraft capable of detonating a nuclear bomb to deflect an asteroid, if it was on a collision course to Earth. The study is a collaboration between the National Nuclear Security Administration, NASA, and two Energy Department weapons labs.
In modern times, numerous impact events on Mars have been detected. Although most have been inferred from the appearance of new impact craters on the planet, some have corresponded to marsquakes felt by the InSight lander. To date, no impacting meteors have been directly observed as a fireball or discovered in space before impact.
