"An asteroid is a minor planet—an object that is neither a true planet nor a comet—that orbits within the inner Solar System."
The study of these small, rocky and icy objects in our Solar System and how they relate to the formation and evolution of planets.
Origins and evolution: The processes that led to the formation of asteroids and comets, and their evolution over time.
Physical characteristics: The physical properties of asteroids and comets, such as size, shape, mass, and density.
Spectroscopy: The study of the interaction of electromagnetic radiation with matter, including the analysis of the light reflected by asteroids and comets.
Composition: The chemical composition of asteroids and comets, including the presence of organic molecules and volatiles.
Interactions with the Sun: How asteroids and comets interact with the Sun, including their trajectories, orbits, and gravitational forces.
Impact dynamics: The physics of asteroid and comet impact events, including their effects on the Earth and other planets.
Cratering: The formation and morphology of impact craters on the surfaces of asteroids and comets.
Exploration: The history and current state of asteroid and comet exploration, including missions by spacecraft and telescopes.
Planetary defense: Strategies for mitigating the risk of asteroid and comet impacts on the Earth.
Astrobiology: The implications of asteroids and comets for the origins and potential for life in the universe.
C-Type Asteroids: These are carbonaceous asteroids that are the most common type found in the Asteroid Belt. They are primarily composed of clay and silicate rocks, and they contain water and other organic materials.
S-Type Asteroids: These are silicaceous asteroids that are also found in the Asteroid Belt. They are composed of stony materials and contain a mix of metallic and non-metallic minerals.
M-Type Asteroids: These are metallic asteroids that are composed of mostly iron and nickel. They are thought to be the cores of ancient, disrupted asteroids.
D-Type Asteroids: These are dark asteroids that are believed to be the remnants of the early Solar System. They reflect very little light and are rich in organic materials.
T-Type Asteroids: These are asteroids with a composition that is similar to comets. They are thought to be transitional objects between comets and asteroids.
Long-Period Comets: These comets take more than 200 years to complete one orbital period around the sun. They are believed to originate from the Oort Cloud, a spherical cloud of icy bodies surrounding the Solar System.
Short-Period Comets: These comets take less than 200 years to complete one orbital period around the sun. They are believed to originate from the Kuiper Belt, a region beyond Neptune that contains billions of icy objects.
Jupiter Family Comets: These comets have orbital periods of less than 20 years and are believed to originate from the Kuiper Belt. They are influenced by Jupiter's gravity and follow highly inclined and elliptical orbits.
Halley-Type Comets: These comets have highly elliptical orbits that bring them close to the sun every 76 years or so. Halley's Comet is the most famous example of this type.
Chiron-Type Comets: These comets have orbits that cross the orbit of Saturn and are believed to be icy bodies from the Kuiper Belt that were captured by Saturn's gravity.
"They are rocky, metallic or icy bodies with no atmosphere. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter."
"Of the roughly one million known asteroids the greatest number are located between the orbits of Mars and Jupiter, approximately 2 to 4 AU from the Sun, in the main asteroid belt."
"Asteroids are generally classified to be of three types: C-type, M-type, and S-type. These were named after and are generally identified with carbonaceous, metallic, and silicaceous compositions, respectively."
"The largest, Ceres, is almost 1,000 km (600 mi) across and qualifies as a dwarf planet."
"The total mass of all the asteroids combined is only 3% that of Earth's Moon."
"The majority of main belt asteroids follow slightly elliptical, stable orbits, revolving in the same direction as the Earth and taking from three to six years to complete a full circuit of the Sun."
"Asteroids have been historically observed from Earth; the Galileo spacecraft provided the first close observation of an asteroid."
"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. JAXA's missions Hayabusa and Hayabusa2 studied and returned samples of Itokawa and Ryugu, respectively. OSIRIS-REx studied Bennu, collecting a sample in 2020 to be delivered back to Earth in 2023."
"NASA's Lucy, launched in 2021, will study ten different asteroids, two from the main belt and eight Jupiter trojans."
"Psyche, scheduled for launch in 2023, will study a metallic asteroid of the same name."
"Near-Earth asteroids can threaten all life on the planet; an asteroid impact event resulted in the Cretaceous–Paleogene extinction."
"The Double Asteroid Redirection Test spacecraft, or DART, was launched in 2021 and intentionally impacted Dimorphos in September 2022, successfully altering its orbit by crashing into it."
"...impacted Dimorphos in September 2022..."
"Different asteroid deflection strategies have been proposed..."
"...Dawn observed Vesta and Ceres. JAXA's missions Hayabusa and Hayabusa2 studied and returned samples of Itokawa and Ryugu, respectively. OSIRIS-REx studied Bennu, collecting a sample in 2020 to be delivered back to Earth in 2023."
"NASA's Lucy, launched in 2021, will study ten different asteroids..."
"The largest, Ceres, is almost 1,000 km (600 mi) across and qualifies as a dwarf planet."
"The total mass of all the asteroids combined is only 3% that of Earth's Moon."
"...approximately 2 to 4 AU from the Sun, in the main asteroid belt."