Chapter 9

Asteroids. More than a video game.

Asteroids are a collection of rocks and dust, half a mile or more in diameter. Scientists believe that they make be leftovers from the Big Bang. (Penny? Penny?) Others believe that they might be fragments of a small planet that was destroyed for unknown reasons.

Most asteroids orbit the sun, in a large belt between Mars and Jupiter. Over a billion fragments reside in this belt, ranging in size from tiny to large. One of the largest is Ceres, an asteroid 637 miles in diameter.

How do asteroids escape from the asteroid belt? Through the Kirkwood Gap, named after the American astronomer, Daniel Kirkwood. He discovered that the belt was separated into two regions by a mysterious gap. Asteroids that enter the gap, shift into an orbit that’s closer to Earth. One out of five asteroids will end up crossing Earth orbit at some point.

A miss is as good as 500,000 miles.

On March 23, 1989, an asteroid passed within half a million miles of hitting the Earth. This is roughly twice the distance between Earth and the Moon. If the asteroid, traveling at 46,000 mph had acually struck the Earth, it would have had a devistating impact of around 20,000 one-megaton hydrogen bombs. It was calculated that the asteroid missed the Earth by 6 hours in its orbital trajectory. Had it struck, there would have been a crater ten miles long and one mile deep.

Asteroids in the past.

The first scientific finding that asteroids were not pieces of alien spacecraft occurred in 1803 in Northern France.

In 1908, an asteroid the size of a small building, crashed near the Stony Tunguska River in Siberia. The force was calculated to be close to 12 megatons of TNT.

In 1984, a Japan Airlines flight saw a mushroom-like cloud 70,000 feet tall and 200 miles wide. The flight landed at a U.S. Airbase in Anchorage, Alaska, fearing that they had flown through radiation. No traces were found.

Eventually scientists concluded that the airliner may have passed through a cloud created by an exploding meteor.

An asteroid named “Icarus” came within 4 million miles of hitting the Earth in 1968. The near miss started the scientific community to thinking that an impact to an asteroid by a missile of some type will change the trajectory of an asteroid to avoid the Earth.

Guess what? Last month, they tested that theory and it worked!

WWW.NASA.GOV/PRESS-RELEASE/NASA-CONFIRMS-DART-MISSION-IMPACT-CHANGED-ASTEROID-S-MOTION-IN-SPACE