International Asteroid Day, observed annually on June 30, seeks to raise awareness about asteroids—their scientific significance as well as the potential hazards they pose. The date commemorates the Tunguska Event of 1908, when a space rock estimated to be 50 to 60 meters wide exploded in the atmosphere over Siberia, Russia. The blast flattened approximately 2,150 square kilometers of forest but did not create an impact crater, as the asteroid disintegrated before reaching the ground.
Asteroids have played a profound role in Earth's history, notably the impact that contributed to the extinction of the dinosaurs about 66 million years ago. This event, known as the Chicxulub impact, involved a roughly 10-kilometer-wide asteroid striking what is now Mexico, leaving a 200-kilometer-wide crater. The collision triggered massive wildfires and released large amounts of soot into the atmosphere, causing climate disturbances that drastically altered life on the planet.
Most asteroids in the solar system are found in the asteroid belt, which orbits the Sun between Mars and Jupiter. While over 1.6 million asteroids have been catalogued, many more remain undiscovered. The largest known asteroid in this belt is Vesta, measuring about 530 kilometers in diameter, whereas some of the smallest asteroids are less than 10 meters across. Collectively, their mass is less than that of Earth's Moon.
Efforts to monitor near-Earth objects are ongoing, primarily led by NASA. According to the agency, the probability of a large asteroid causing widespread damage on Earth within the next century is very low. Nonetheless, smaller asteroids roughly the size of a house enter the atmosphere about once every ten years, producing bright fireballs and sonic booms capable of breaking windows in nearby areas.
Asteroid naming follows guidelines set by the International Astronomical Union, which recommends that names be inoffensive, original, and limited to a single word of no more than 16 characters. Although naming asteroids after pets is generally discouraged, there have been exceptions such as the asteroid 2309 Mr Spock, named by astronomer James B. Gibson in 1971 after his cat.
Asteroids are remnants from the early solar system, roughly 4.6 billion years old, composed of rock, metal, and other materials. Some exhibit unique features, including rings or small moons. Notably, asteroid 16 Psyche is a metallic body believed to contain vast quantities of iron and nickel, with an estimated value of $700 quintillion, offering significant scientific interest and economic potential.