13.1 Asteroids
3 min read•june 12, 2024
, remnants of our solar system's early days, offer clues about its formation. These rocky bodies, mostly found in the between Mars and Jupiter, come in various types and compositions. Some even venture close to Earth, sparking scientific interest and exploration.
Space agencies have sent missions to study asteroids up close. These missions have revealed fascinating details about composition, structure, and history. From rubble piles to water-bearing minerals, each discovery brings us closer to understanding our cosmic neighborhood.
Asteroid Characteristics and Exploration
Discovery and orbits of asteroids
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- Asteroids first discovered in early 19th century
- Giuseppe discovered first asteroid, , in 1801
- Several more asteroids discovered in following years (, , )
- Most asteroids orbit Sun in between Mars and Jupiter
- Asteroid belt located approximately 2.1 to 3.3 AU from Sun (1 AU = Earth-Sun distance)
- Asteroids in belt have orbital periods ranging from about 3 to 6 years
- : regions in the asteroid belt with fewer asteroids due to orbital resonances with Jupiter
- Some asteroids, called (), have orbits that bring them close to Earth
- NEAs classified into three main categories based on orbits: , , and
- Aten asteroids have orbits entirely within Earth's orbit
- Apollo asteroids have orbits that cross Earth's orbit
- Amor asteroids have orbits entirely outside Earth's orbit but still come close
- share same orbit as a planet, typically Jupiter
- Trojans located at L4 and L5 , stable gravitational regions 60° ahead of and behind planet in its orbit (Greek camp and Trojan camp)
Types and compositions of asteroids
- (carbonaceous) asteroids
- Make up about 75% of known asteroids
- Composed of clay and silicate rocks, with some organic compounds (carbon, water)
- Relatively low (reflectivity) of 0.03 to 0.09
- Mostly found in outer regions of asteroid belt
- (silicaceous) asteroids
- Make up about 17% of known asteroids
- Composed of silicate materials and nickel-iron
- Relatively high albedo compared to , ranging from 0.10 to 0.22
- Mostly found in inner regions of asteroid belt
- (metallic) asteroids
- Make up about 8% of known asteroids
- Composed mainly of nickel-iron
- Relatively high albedo, similar to
- Mostly found in middle region of asteroid belt
- Other less common types include (basaltic), (enstatite), (primitive)
- is used to determine asteroid composition by analyzing reflected light
Formation and Evolution of Asteroids
- Asteroids are remnants of , small bodies that formed in the early solar system
- Some asteroids collide and break apart, creating smaller fragments
- Fragments that reach Earth's surface are called , providing valuable information about asteroid composition
- on asteroids and other bodies provide evidence of past collisions
Spacecraft missions to asteroids
- NASA's Near Earth Asteroid Rendezvous (NEAR) Shoemaker mission (1996-2001)
- Studied near-Earth asteroid
- Discovered has density similar to Earth's crust, suggesting solid composition
- Found evidence of layer of (loose surface material) on asteroid's surface
- NASA's Dawn mission (2007-2018)
- Studied dwarf planet Ceres and asteroid Vesta
- Discovered Ceres has differentiated interior with rocky core and icy mantle
- Found evidence of past water activity on Ceres, including bright salt deposits in craters
- Revealed Vesta has differentiated interior and history of volcanic activity
- Japan's Hayabusa mission (2003-2010)
- Studied and sampled near-Earth asteroid
- Discovered is a "rubble pile" asteroid, composed of numerous small rocks held together by gravity
- Successfully returned small amount of asteroid material to Earth for analysis
- NASA's OSIRIS-REx mission (2016-2023)
- Studying and sampling near-Earth asteroid
- Found evidence of water-bearing minerals on Bennu's surface
- Successfully collected sample of Bennu's surface material in October 2020, with sample scheduled to return to Earth in September 2023
Key Terms to Review (42)
101955 Bennu: 101955 Bennu is a near-Earth asteroid that has been the subject of intense scientific study due to its unique characteristics and potential impact on Earth. It is a carbonaceous asteroid, meaning it is composed of carbon-rich materials, and is considered a potentially hazardous asteroid (PHA) due to its size and orbit.
25143 Itokawa: 25143 Itokawa is a small near-Earth asteroid that has been extensively studied by various space missions. It is an important object in the field of asteroid research, providing valuable insights into the composition, structure, and evolution of these celestial bodies.
433 Eros: 433 Eros is a large near-Earth asteroid that was the first asteroid discovered to have a small natural satellite. It is one of the largest near-Earth objects and has been extensively studied by scientists due to its unique characteristics and potential for providing insights into the formation and evolution of the Solar System.
Albedo: Albedo is the measure of the reflectivity of a surface, specifically the ratio of the amount of light or radiation reflected by a body or surface to the amount of light or radiation incident upon it. It is an important concept in understanding the energy balance and thermal properties of planetary bodies, as well as the behavior of various solar system objects.
Amors: Amors are a group of near-Earth asteroids that have orbits that cross the orbit of Earth, but do not cross the orbit of Mars. They are named after the Roman god of love, Amor, and are characterized by their unique orbital paths that bring them close to Earth's orbit.
Amors are an important class of asteroids in the context of 13.1 Asteroids, as they provide insights into the formation, evolution, and potential hazards of small bodies in the solar system. Understanding the properties and behavior of Amors can help scientists better predict and mitigate the risks posed by these celestial objects.
Apollos: Apollos was an early Christian evangelist and teacher who played a significant role in the development of the early Christian church. He was known for his eloquent preaching and deep understanding of the Scriptures, particularly the Old Testament.
Asteroid: An asteroid is a small, rocky body that orbits the Sun. Asteroids are remnants of the early solar system and provide valuable insights into the formation and evolution of our planetary system. They are closely related to the topics of cosmic influences on Earth's evolution and the study of asteroids themselves.
Asteroid belt: The asteroid belt is a region of space located between the orbits of Mars and Jupiter where the majority of asteroids in our solar system are found. It contains a vast number of irregularly shaped bodies composed mostly of rock and metal.
Asteroid Belt: The asteroid belt is a region in the Solar System located between the orbits of Mars and Jupiter, where a large number of small rocky objects, known as asteroids, orbit the Sun. This belt is a key feature of the Solar System and plays an important role in understanding the formation and evolution of the planets.
Asteroids: Asteroids are small, rocky bodies that orbit the Sun, primarily found in the asteroid belt between Mars and Jupiter. They vary in size and shape, with some being large enough to be considered dwarf planets if they were spherical.
Atens: Atens are a group of near-Earth asteroids that have orbits that are entirely contained within Earth's orbit around the Sun. They are named after the asteroid 2062 Aten, the first of this class of objects to be discovered.
C-type: C-type asteroids are a class of carbonaceous asteroids that are dark in color and have a composition rich in carbon compounds. They are the most common type of asteroids found in the main asteroid belt and are believed to be some of the most primitive and unaltered objects in the solar system.
C-type asteroids: C-type asteroids are carbonaceous asteroids that make up about 75% of known asteroids. They are dark in appearance and contain a high percentage of carbon, along with rocks and minerals.
Ceres: Ceres is the largest object in the main asteroid belt between the orbits of Mars and Jupiter. It is classified as a dwarf planet, the only dwarf planet located in the inner solar system. Ceres plays a significant role in our understanding of the formation and evolution of the solar system, as well as the study of asteroids and planetary defense.
Dactyl: Dactyl is a small natural satellite of the asteroid 243 Ida. It was discovered by the Galileo spacecraft in 1993 and is notable for being one of the first confirmed asteroid moons.
E-type: E-type asteroids are a class of asteroids that are characterized by their distinctive spectral features, indicating a surface composition primarily composed of the mineral enstatite. These asteroids are named after the prototype, asteroid 2867 Šteins, which was the first asteroid of this type to be discovered and studied in detail.
Eros: Eros is an S-type asteroid in near-Earth orbit, known for being one of the largest such asteroids. It was extensively studied by NASA's NEAR Shoemaker spacecraft.
Gaspra: Gaspra is an asteroid in the main asteroid belt between Mars and Jupiter. It was the first asteroid to be closely imaged by a spacecraft, specifically Galileo in 1991.
Ida: Ida is an asteroid in the Koronis family located in the main asteroid belt between Mars and Jupiter. It is notable for having its own moon, Dactyl.
Impact Craters: Impact craters are depressions formed in the surface of a planet, moon, or other solid body in the solar system by the high-speed impact of a meteoroid, asteroid, comet, or other celestial object. These craters provide valuable information about the geological history and evolution of planetary bodies.
Itokawa: Itokawa is a peanut-shaped, near-Earth asteroid that was the target of the Japanese Hayabusa mission. It represents a rubble-pile structure, composed of many smaller boulders held together by gravity.
Juno: Juno is the name of a NASA space probe that is currently orbiting the planet Jupiter, studying the giant planet's composition, magnetic field, and atmospheric dynamics in unprecedented detail. This mission is providing valuable insights into the formation and evolution of Jupiter and the entire Solar System.
Kirkwood Gaps: Kirkwood gaps are regions in the asteroid belt where there is a noticeable lack of asteroids. These gaps occur at specific orbital distances from the Sun, where the orbital period of an asteroid would be a simple fraction of Jupiter's orbital period, leading to gravitational resonances that clear out material from these regions over time.
Lagrange Points: Lagrange points are specific locations in the orbital plane of two large bodies, such as a planet and its moon, where a smaller object can maintain a stable orbit relative to the two larger bodies. These points are named after the Italian-French mathematician Joseph-Louis Lagrange, who first described them in the 18th century.
M-type: M-type asteroids are a class of asteroids characterized by their high metallic content, typically composed of iron and nickel. These asteroids are believed to be the remnants of the cores of larger planetesimals that were disrupted during the early formation of the solar system.
M-type asteroids: M-type asteroids are a classification of asteroids that primarily consist of metallic iron and nickel. They are thought to be remnants of the metallic cores of differentiated protoplanets.
Meteorites: Meteorites are solid pieces of extraterrestrial material that have survived passage through the atmosphere and landed on the surface of a planet or moon. They are remnants of asteroids or other celestial bodies that have broken apart during their journey through space.
Near-Earth Asteroids: Near-Earth asteroids (NEAs) are a class of asteroids whose orbits bring them into close proximity with Earth. These celestial bodies are of particular interest to astronomers and space agencies due to their potential to impact our planet and the valuable information they can provide about the formation and evolution of the solar system.
NEAs: NEAs, or Near-Earth Asteroids, are a class of asteroids whose orbits bring them into close proximity with Earth's orbit. These objects are of particular interest to astronomers and planetary scientists as they provide valuable insights into the formation and evolution of our solar system.
NEAs are defined as asteroids with orbits that bring them within 1.3 astronomical units (AU) of the Sun, meaning they can come within 0.3 AU of Earth's orbit. This proximity makes them potentially hazardous, as a collision with Earth could have devastating consequences.
P-type: P-type refers to a specific type of asteroid composition that is rich in carbon and dark in appearance. These asteroids are believed to be some of the most primitive and unaltered objects in the solar system, providing valuable insights into the early formation and evolution of the planets.
Pallas: Pallas is the second-largest asteroid in the main asteroid belt, after Ceres. It is a large, irregularly shaped rocky body that orbits the Sun between the orbits of Mars and Jupiter, and is considered one of the most massive and largest of the main-belt asteroids.
Piazzi: Giuseppe Piazzi was an Italian astronomer who discovered the first asteroid, Ceres, in 1801. His discovery marked the beginning of asteroid studies in modern astronomy.
Planetesimals: Planetesimals are small celestial objects that formed from dust and gas in the early solar system. They serve as the building blocks of planets through a process called accretion.
Planetesimals: Planetesimals are the small, rocky or icy bodies that formed the building blocks of the planets in the early stages of the Solar System's development. These objects, ranging from just a few kilometers to hundreds of kilometers in size, gradually accumulated through the process of accretion to eventually create the larger planetary bodies we see today.
Regolith: Regolith is the layer of loose, unconsolidated rock and dust that covers the surface of a planetary body, such as the Moon, Mercury, or Mars. It is the result of the continuous breakdown and weathering of the underlying bedrock through various geological processes.
S-type: S-type asteroids are a class of asteroids that are characterized by their silicate-rich composition, similar to the stony meteorites known as ordinary chondrites. These asteroids are thought to be remnants of the early solar system's formation and provide valuable insights into the composition and evolution of the inner solar system.
S-type asteroids: S-type asteroids are a class of asteroids that are composed primarily of silicate minerals and nickel-iron. They are commonly found in the inner asteroid belt.
Spectroscopy: Spectroscopy is the study of the interaction between matter and electromagnetic radiation, which provides valuable information about the composition, temperature, and motion of celestial objects. This technique is widely used in astronomy to analyze the properties of stars, galaxies, and other cosmic phenomena.
Trojan Asteroids: Trojan asteroids are a group of asteroids that share an orbit with a planet, typically leading or following the planet by approximately 60 degrees. These asteroids are named after characters from Homer's Iliad and reside in the Lagrangian points of the planet's orbit, where the gravitational forces of the planet and the Sun balance out, allowing the asteroids to maintain their position.
V-type: V-type asteroids are a class of asteroids that exhibit spectral characteristics similar to the mineral Vesta, the second-largest asteroid in the Solar System. These asteroids are believed to have compositions that are closely related to the composition of Vesta, making them valuable targets for understanding the formation and evolution of the Solar System.
Vesta: Vesta is one of the largest and most well-studied asteroids in the Solar System. It is the second-largest member of the asteroid belt, located between the orbits of Mars and Jupiter. Vesta's unique characteristics and role in the Solar System make it an important subject of study in the fields of astronomy, planetary science, and asteroid exploration.
Wolf: Wolf is the name given to a specific group of asteroids. These asteroids are important for understanding the composition and dynamics of the asteroid belt.