Comets, Meteors and Asteroids

[Jim Colyer]

The solar system and everything in it is 4.6 billion years old. This includes the sun, planets and their moons, comets, meteors and asteroids.

 

Comets are scraps left over from the formation of the solar system. In that early period, there was a lot of debris. Craterization took place on a massive scale. Comets orbit the sun. They develop tails as the sun melts ammonia and methane. Tails extend millions of miles and point away from the sun, forced out by the solar wind. Halley's comet goes out past Neptune, returning every 75 years. Halley was not the first to see his comet but the first to predict its return.

 

I saw comet Ikeya-Seki on Halloween morning, 1965. It was dim and fuzzy but worthwhile. Kohoutek bombed. I saw Hyakutake in 1996 and Hale-Bopp in 1997.

 

It took 30 years to see my second comet, which I spotted the morning of March 24, 1996. Hyakutake was as bright as the Big Dipper stars and extended its handle. It was fuzzy with no discernible tail. Two mornings later, it had moved by the Little Dipper. The morning of March 27, it was under the North Star. Hyakutake upstaged Hale-Bopp which had gotten advanced publicity. The Japanese are comet hunters.

 

Shoemaker-Levy 9's impact with Jupiter gave astronomers their first glimpse of a collision in space. Jupiter is like a vacuum cleaner, sucking up stuff and protecting Earth.

 

In the early 1960's, I began watching the Perseids. The Perseids is the best meteor shower and occurs annually in August. The night of August 11 and morning of August 12, 1964, I counted 351 meteors. Toward morning, they were dropping in the east like snowflakes. Many were bolides, leaving bright trails. The best one appeared after daybreak. Cousin Larry was yelling, and I looked up to see a meteor as large as a full moon. It was exploding and changing colors.

 

Meteor showers are associated with comets. As comets orbit the sun, they leave behind debris. Meteoroids get strung out along their paths. Most of the stuff which enters our atmosphere is no larger than sand. Meteors are vaporized by friction about a hundred miles up. In any shower, meteors emanate from a point in the sky called the radiant. Showers are named after the constellations behind their radiants. We see more meteors toward morning because we are driving into them. Perseids are associated with comet Swift-Tuttle.

 

Meteorites are objects which survive and fall to earth. Meteorites are composed of iron and nickel. Meteor Crater near Winslow, Arizona is evidence of a large meteorite which hit 50,000 years ago. It is privately owned.

 

200 impact craters have been found around the world. There is one is near Odessa, Texas. Wolf Creek Crater is in Australia. Thousands of meteorites have been found on ice in Antarctica. O. Richard Norton says meteorites are pieces of asteroids. The largest meteorite found in the United States came from Willamette, Oregon. I saw it in the American Museum of Natural History in New York.

 

There is one instance of a person being hit by a meteorite. In 1954, a woman in Alabama was sleeping on her couch when a meteorite crashed through the roof. It ricocheted and hit her in the side, inflicting a bruise.

 

Craters have been mapped from Space Shuttles. Comets and asteroids create craters. The idea that dinosaurs were killed by a large asteroid is now accepted. Scientists point to Chicxulub (Cheek-shoe-lube) crater in Mexico's Yucatan peninsula as being the impact which killed not only the dinosaurs but two-thirds of all species. That is pinning it down. The evolution of life may be driven by impacts.

 

Something hit Siberia in Russia in 1908. It is known as the Tunguska Event. Trees were flattened but no crater was found. The comet or asteroid vaporized before impact.

 

Earth's atmosphere acts like sandpaper, constantly smoothing things out. Water erodes craters. Otherwise, the earth would look like the moon. Plate tectonics also reshape the earth.