- Asteroids are rocky, airless remnants from the early formation of the solar system about 4.6 billion years ago.
- Often referred to as minor planets or planetoids, they are primarily found in the asteroid belt—a region of space between the orbits of Mars and Jupiter where the gravitational influence of nearby planets prevented these rocky fragments from coalescing into a full-sized planet. While they vary greatly in size, from a few meters to hundreds of kilometers in diameter, most asteroids are irregularly shaped due to their small mass and lack of sufficient gravity to become spherical.
- Composed mainly of rock and metal, asteroids are categorized into different types based on their composition and reflectivity. The three broadest classifications are C-type (carbonaceous), S-type (silicaceous), and M-type (metallic). C-type asteroids, which are the most common, are rich in carbon and often extremely dark. S-type asteroids are made up mostly of silicate materials and nickel-iron, while M-type asteroids consist largely of metallic iron and nickel. These compositional differences offer valuable clues about the conditions and processes present during the solar system’s formation.
- Asteroids play a crucial role in understanding planetary science. Some are believed to be the leftover building blocks of planets, while others are fragments of larger bodies shattered by collisions.
- Occasionally, asteroids are perturbed from their stable orbits and may pass near Earth. These are known as Near-Earth Objects (NEOs), and a small number have collided with Earth in the past, contributing to mass extinction events, such as the one that ended the reign of the dinosaurs. This potential threat has spurred ongoing efforts to monitor and devise strategies for planetary defense.
- In recent years, space missions such as NASA’s OSIRIS-REx and Japan’s Hayabusa2 have revolutionized our understanding of asteroids by visiting, sampling, and returning material from them. These missions have provided unprecedented insights into the composition, structure, and evolution of these celestial bodies. In addition to their scientific value, asteroids are also considered potential resources for future space exploration. They may harbor water, metals, and other raw materials that could support space industries or long-term human missions beyond Earth.
