Cross-section of Boisse’s hypothetical meteorite-planet. Fragmentation of this sphere was believed to have given rise to the following divisions of meteorites:
The iron meteorites came from A, the dense nickel-iron core.
The stony-iron meteorites came from B, the intermediate zone of cellular nickel-iron and silicate minerals.
The stony meteorites came from C, the outer zone of silicate minerals in which relatively little or no nickel-iron is present. The chondrites were believed to come from the inner portion of this zone; the achondrites, from the outer portion.
There are several other theories of the origin of meteorites interesting enough to mention. The early view that the meteorites were debris thrown out by ancient volcanoes on the moon or recent ones on the earth came to be discredited largely on physical grounds. On the other hand, extremely violent primordial volcanoes on the earth (not the weak ones of historic times, like Aetna or Vesuvius) could have ejected material that in much later times fell, and continues to fall back on our globe. This theory has not been ruled out and it still receives support, for example, from some authorities in the U.S.S.R. These same Russian scientists take most seriously a suggestion that the meteorites (and comets as well) were thrown out by volcanoes believed to exist on the planet, Jupiter—a theory dating back almost a century to the English astronomer, R. A. Proctor.
Some scientists believe that meteorites represent the congealed remains of gaseous bolts of matter ejected by the sun. Others interpret them as fragments of comets that have been torn apart by passing too close to the sun, which is the most powerful gravitational center in the Solar System.
Chemists, geologists, astronomers, and physicists—as well as the meteoriticists themselves—are constantly working toward a solution of the problem of the meteorites. Where do these bodies come from? What can we learn from them about their age and origin and about the age and origin of our Solar System? Years may be required, but eventually the riddle of the meteorites will be solved by the patient, concerted efforts of men and women of science.
Collapsed mine buildings in the bottom of the Canyon Diablo meteorite crater. A shaft was put down here in one of several unsuccessful attempts to locate the main mass of the meteorite. See pp. [44]-52.