Asteroid Zooms By Earth
Jan. 27, 2012
An asteroid–a 36-foot (11-meter) space rock named 2012 BX3–hurtled past Earth today, coming as close as 37,280 miles (60,000 kilometers). “It’s one of the closest approaches recorded,” noted Gareth Williams, associate director of the Minor Planet Center at Cambridge, Massachusetts. “It makes it in to the top 20 closest approaches, but it’s sufficiently far away . . . that there’s absolutely no chance of it hitting us.” Scientists believe that asteroids are chunks of material left over from the formation of the solar system. The gravitational pull of the planet Jupiter probably prevented these pieces from coming together to form a full-sized planet. Some asteroids may represent the nuclei (cores) of comets that are no longer active.
The asteroid Ida and its tiny moon Dactyl appear in a photograph taken by the U.S. spacecraft Galileo. Dactyl may be a piece of Ida that broke away during a collision with another asteroid. NASA/JPL/Galileo Project
The atmosphere protects Earth from most asteroid strikes. Air friction causes an asteroid smaller than about 160 feet (50 meters) in diameter to disintegrate before it can reach the surface and cause damage. Larger asteroids can impact the environment of the entire globe. The impact of an asteroid with a diameter of around 0.6 mile (1 kilometer) would kick large amounts of dust into the atmosphere. The dust would block sunlight, which would cool the air for many months. One such strike occurred 65 million years ago on Mexico’s Yucatan Peninsula. Many scientists think environmental damage caused by the collision led to a mass extinction. The extinction eliminated huge numbers of species, including the dinosaurs.
Additional World Book articles:
- Dawn
- Eros
- Vesta
- When Worlds and Comets Collide (a special report)
- What Has Caused Mass Extinctions (a special report)
