Montshire Minute: Asteroids

Originally aired during the week of August 3, 1998

Monday

Thanks to two summer blockbuster movies about giant rocks from outer space slamming into earth, there's been a lot of attention focused on asteroids. Believe it or not, material from outer space is bombarding the earth's atmosphere all the time. An average of 100 TONS of meteorites reach the Earth's atmosphere every day--most of this stuff burns up long before it hits land or water. Asteroids are smaller than planets, and are sometimes called planetoids. The smallest are only a few thousand feet in diameter, but one of the largest, Ceres, is 620 miles across. Asteroids are part of the debris left over when the Sun and its planets were formed, fragments that never got it together enough to form another planet or moon. The asteroid belt forms a band that orbits the sun in the gap between Mars and Jupiter. Sometimes asteroids ram into each other in the belt, creating meteors that shoot off from the orbit of the belt and start their own course, which can coincide with the Earth's own orbit.

Tuesday

It's easy to get comets, meteors and asteroids confused. Comets, like Hale-Bopp, which was visible to the naked eye in the spring of 1997, are made of dust, ice and frozen gasses. You can think of them as very large and dirty snowballs. Asteroids, on the other hand, are basically big, huge rocks. I mean really huge, anywhere from 3,000 feet to 600 miles in diameter. Based on the discovery of some soil samples taken off the coast of Florida recently, many scientists are now convinced that a rogue asteroid walloped into the earth 65 million years ago, killing off the dinosaurs and most other life on the planet. Meteors are small fragments of comets or asteroids, ranging in size from dust grains to a large house. When meteors pass through the earth's atmosphere and land on the ground, we call them meteorites.

Wednesday

Last March, the world was startled to learn that a big asteroid dubbed XF11 was due to crash into our planet earth in the year 2028. A day later, more exact calculations by scientists concluded that the asteroid would actually miss the earth, and we all breathed a big sigh of relief, knowing that our vacation plans for 2028 were still intact. Astronomers beleive there may be as many as 2,000 asteroids big enough to do put a serious hurt on our planet and that might be on a collision course with us. Only about one-tenth of that number have been discovered. It takes many observations and calculations to track an asteroid's orbit precisely enough to decide if there is any risk. While there may be no immediate danger of a direct hit, most asteroids with orbits crossing Earth's will collide with us at some point over the next few hundreds of millions of years.

Thursday

Many scientists believe that an asteroid about six miles wide hit the Earth near the Yucatan Peninsula in the Gulf of Mexico 65 million years ago, traveling 100 times faster than a speeding bullet. Top that, Superman. The crater that they found is the largest one on Earth. When the asteroid hit, it sent up tons of dust particles into the atmosphere, blocking out the sun for a long time. Earth was probably a cold, dark place for many years, and dinosaurs, along with most other life on the planet, died out under these harsh conditions. Astronomers estimate that the earth is struck an average of once every 100,000 years by an object one kilometer in diameter. A collision with an object this size would have more energy than all of the nuclear weapons now on earth.

Friday

NASA has stepped up its effort to search for asteroids that may be on a collision course with earth. But NASA's total spending of $3 billion on this project is still far short of the $50 million per year that NASA's 1992 SpaceGuard study said would be needed. Still, the agency is trying to identify all objects larger than 1 kilometer in diameter within the next ten years. What do we do if we detect an asteroid headed straight for Earth? So far, the only source of energy powerful enough to deflect an asteroid like the one that struck the Earth 65 million years ago is nuclear. Scientists are exploring the idea of sending a nuclear device into space that, if exploded on or near the asteroid, could sort of "kick" it off course. Perhaps new technologies will exist hundreds or thousands of years in the future that can deflect an incoming cosmic cannonball.