Asteroids

Asteroids

Between the orbits of Mars and Jupiter are countless asteroids, tiny terrestrial planets. The largest are a few hundred kilometers across. Many of them have oblong shapes and are tumbling throught space. In some cases there seem to be tow or more asteroids in tight mutual orbits. Collisions among the asteroids happen frequently, and occasionally a piece is chipped off and accidentally intercepts the Earth, falling to the ground as a meteorite. In the exhibits, on the shelves of our museums are the fragments of distant worlds.

The asteroid belt is a great grinding mill, producing smaller and smaller pieces down to motes of dust. The bigger asteroidal pieces, along with the comets, are mainly responsible for the recent craters on planetary surfaces. The asteroid belt may be a place where a planet was once prevented from forming because of the gravitational tides of the giant nearby planet Jupiter; or it may be the shattered remains of a planet that blew itself up. This seems improbable because no scientist on Earth knows how a planet might blow itself up, which is probably just as well.

As far as we know, the first essentially nonmystical attempt to explain a historical event by cometary intervention was Edmund Halley’s proposal that the Noachic flood was the casual Choc of a Comet. Image : Psychodelic Racing Track © Elena

The rings of Saturn bear some resemblance to the asteroid belt: trillions of tiny icy moonlets orbiting the planet. They may represent debris prevented by the gravity of Saturn from accreting into a nearby moon, or they may be the remains of a moon that wandered too close and was torn apart by the gravitational tides. Alternatively, they may be the steady state equilibrium between material ejected from a moon of Saturn, such as Titan, and material falling into the atmosphere of the planet.

Jupiter and Uranus also have ring systems, discovered only recently, and almost invisible from the Earth. Whether Neptune has a ring is a problem high on the agenda of planetary scientists. Rings may be a typical adornment of Jovian-type planets throughout the cosmos.

Major recent collisions from Saturn to Vegus were alleged in a popular book, Worlds in Collision, published in 1950 by a psychiatrist named Immanuel Velikovsky. He proposed that an object of planetary mass, which he called a comet, was somehow generated in the Jupiter system. Some 3,500 years ago, it careered in toward the inner solar system and made repeated encounters with the Earth and Mars, having as incidental consequences the parting of the Red Sea, allowing Moses and the Israleites to escape from Pharaoh, and the stopping of the Earth from Rotating on Joshua’s command. It also caused, he said, extensive vulcanism and floods. Velikovsky imagined the comet, after a complicated game of interplanetary billiards, to settle down into a stable, nearly circular orbit, becoming the planet Venus – which he claimed never existed before then.