Glass from the Lost Planet

Tektites are bits of semitransparent glassy stuff, mostly black or dark green, found in many parts of the world. They cannot be explained as earthly minerals, so most scientists who have studied them believe that they come from space. In The Scientific Monthly, Physicist Ralph Stair of the National Bureau of Standards tells how he thinks they were formed and how they got scattered so widely.

Ordinary meteorites are believed to be bits of a "lost planet" that revolved in an orbit between Mars and Jupiter. For some reason, it broke up and filled the solar system with large and small debris. Nickel-iron meteorites are thought to be fragments of its dense interior, while stony meteorites are made of lighter material from near the planet's surface.

According to Stair's theory, tektites came from the lost planet too. He thinks that on its surface was light, glassy material that had separated like cream as the heavier metal and rock sank toward the center of the planet. This separation may have happened on the earth too, but water erosion destroyed the glass.

On the lost planet there was no water, so the glass on its surface survived until the final breakup. Then chunks of it sailed around the solar system along with chunks of metal and rock. When they hit the earth's atmosphere, the glass shattered into small fragments as soon as it began to get hot. The fragments fell to earth as tektites. When a fragment had the right shape to keep it from tumbling as it moved through the air, the molten glass that was wiped off the forward end frequently solidified as "wings" or an "apron" attached to the rear end. The glass that was melted can often be distinguished from the rest by microscopic examination.

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