Catch a Falling Star

Catch a Falling Star

During the most recent ice age, a giant ground sloth (Megatherium) was peacefully feeding on a leafy tree when it noticed a light in the sky. The light appeared motionless but became brighter and larger by the second. The impossible was about to happen. The ever—growing light was a four—pound stony meteorite on a collision course with the sloth. It hit like a bullet from a high—powered rifle. Broken skeletal remains and their association with the missile from outer space leave no doubt. This event some 20,000 years ago is the earliest known instance of a living creature being injured by a meteorite.

Anyone who examines the dark sky on a clear night should see a "shooting star" every 10 to 15 minutes. These streaks of light are really sand— to pea—sized bits of comets, billions of which enter our atmosphere each day at speeds 50 times faster than a rifle bullet. Nearly all of them disintegrate into dust, but the total increases the weight of the earth by about 25 tons of interplanetary detritus each day.

Occasionally a large missile, four pounds or more, will get through the atmosphere and strike the earth; such meteorites are usually fragments from asteroids. Between the orbits of Mars and Jupiter is the asteroid belt, sort of a celestial rock garden consisting of billions of rocks that never coalesced into a planet when the solar system was being formed. These rocks are constantly colliding, and pieces break off. The force ejects fragments into another orbit that may take the extraterrestrial rock on a collision course with the earth. The ice age sloth mentioned above was a victim of an asteroid fragment.

Reports have surfaced of persons being struck by meteorites. One, a monk killed in Milan in 1650, is unsubstantiated because "a rock falling from the sky" was not an accepted phenomenon in those days. A 1954 report of a woman being struck by a 10—pound meteorite that burst through her roof, bounced off a radio, and bruised her leg has been authenticated. Considering the number of things that fall from the sky, it must seem surprising that only a few questionable injuries to living creatures can be dredged up in 20,000 years. Even a confirmed pessimist would scarcely run for cover with those odds.

An estimated 500 meteorites a year survive passage through the atmosphere and strike the earth. Throughout history, only about 2,100 separate meteorites have been validated. Recent exploration in the Antarctic has almost doubled that number. Of course, many meteorites break up at or before impact, so myriad fragments occur.

An unusual episode occurred in Wethersfield, Connecticut, on April 8, 1971. Several citizens of the town noticed a light in the sky. It didn't move but became increasingly brighter and somewhat larger. As the ice age sloth would have known, it was a meteorite about to collide with the town of Wethersfield. It struck a house, leaving a large hole in the roof, and bounced around the interior of the house, damaging some furniture but harming no one.

The incident did not appear unusual until November 8, 1982, just 11 years later. Some of the same citizens of Wethersfield noticed the same type of brilliant motionless light in the sky. This could mean only one thing: a meteorite was coming straight toward them. Having survived its fiery passage through the atmosphere, the six—pound, grapefruit—sized meteorite crashed through the roof of a house and then through the second— and first—floor ceilings. It came to rest in the dining room at the end of a trail of plaster and splinters. This impact was less than a mile from where the earlier meteorite had struck. Like most meteoric debris, the meteorite was not hot when it landed, had burned nothing, and was cool to the touch.

That two objects from space would land within a mile of each other is infinitely more incredible than the fact that so few creatures have been hit by space debris. Space is so vast, and the earth is so small a target that it is only because of the huge number of missiles that fall through the sky that the earth is hit at all.

The above incidents involved asteroid fragments of 10 pounds or less. But larger asteroids, several over 100 miles in diameter, have elliptical orbits that at times cross the earth's orbit. Scientists estimate that at least 1,500 asteroids large enough to be measured in miles have elliptical orbits and could collide with the earth some day. Knowing their orbits, scientists can predict a collision. By the time it occurs we hope to have the capability of either destroying the asteroid or deflecting its orbit to make it miss the earth. Thank goodness for a small—sized earth!

Meteorites in the 50,000—ton range appear to strike the earth every 100,000 years or so. Meteor Crater, in Arizona, is four—fifths of a mile in diameter and 575 feet deep, the result of a collision with a meteorite that fragmented upon impact 50,000 years ago. Near misses have occurred. Several asteroids, each less than a mile in diameter, earned that title in recent times. Hermes, in 1937, came within 540,000 miles of the earth, and Icarus, in 1968, passed within six million miles of our planet. Then, in March 1989, an asteroid at least a half—mile across, millions of tons of rock moving at 44,000 miles per hour, shot by the earth at less than twice the distance of the moon. This is so close that it is considered a cosmic near miss. An impact would have been equivalent to the explosion of 20,000 one—megaton hydrogen bombs. It would have left a crater 10 miles across and about a mile deep.

This asteroid, now known as 1989FC, orbits the sun once a year in a regular elliptical path, and it most certainly will be back. Eventually either it will collide with the earth or our planet, with a far superior gravitational influence, will sling it away into another orbit.

No one saw 1989FC go by. It was discovered by a scientist accidentally when he examined a series of photographs taken on March 31 that year with an 18—inch telescope at Palomar Observatory in California. Working backward in time after calculating the orbit, he realized that 1989FC had crossed earth's orbit on March 23. Had the earth been at that same point in its orbit on that day, the result would have been the aforementioned catastrophe.

The asteroid missed earth by a mere six hours. Were you feeling especially lucky on March 23, 1989?

From the book: 
Petrified Lightning