Some considerations with regard to large comets:

by Bob Kobres


A major difference in possible damage to the biosphere across the potential physical size range of Earth-orbit-crossing objects—EOCOs—is the increased capacity for larger EOCOs to produce adverse effects without a direct impact. In other words, an EOCO 1 km across, with sufficient relative velocity to avoid being captured by Earth’s gravity, could come within 1,000 km of Earth’s surface and cause no problem; a 100 km across EOCO with the same velocity is not apt to make such a clean get away.

For one thing, a 100 km diameter EOCO is most likely to be a structurally weak comet-type object. If the object is still active, the space around it is going to contain pieces of various size that have been decoupled physically, but not gravitationally, from its surface. These loosely bound satellites are not likely to be tidy aerodynamic spheres; initially they would be more apt to retain some of the surface geometry of the object that spawned them. What this implies is that the weakly attached debris traveling along with an active comet-type EOCO could deposit a great deal of energy into the biosphere by way of interacting with Earth’s atmosphere over a large area. This, I suspect, is the type of event that produced the Carolina Bays.

Allowing that the Carolina Bays could have been formed by such a debris shower, there are some further observations that are pertinent. The west to east orientation of the elliptical Carolina Bay features suggests that the fireball phenomenom was traveling in the direction of Earth’s spin—counterclockwise as viewed from above the North Pole. This means the hypothetical large comet had to have made a close approach in one of four ways:

Of the four possibilities, I favor the second—a near miss to the rear—as a potential producer of Carolina Bays. This seems more probable for three reasons:

Another factor to consider with a large comet-type object coming deep within Earth’s gravity well is the likelihood of the object being pulled apart in a fashion similar to the Shoemaker-Levy 9 event. It is even conceivable that a close pass could occur which would produce some fragments with too little velocity left to leave Earth’s gravitational influence and so these pieces become short lived satellites of Earth. Objects captured this way would be unlikely to fall into stable orbits and so would eventually either collide with the Earth or Moon or be tossed out of Earth orbit by combined gravitational influence.

The point I attempt to make here is that we do not presently know enough about the range of interaction possibilities to rule out impact related phenomena as the cause of Carolina Bays. There are known comet-type objects with diameters greater than 100 km, Chiron for an example. Unless we discover a law that prevents objects of this size from swinging by Earth, we must assume it is a possible situation. Having pondered this potential for some time now, I personally feel fortunate that we indeed have the opportunity to investigate what caused the Carolina Bays.

bobk 97


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The content and opinions expressed on this Web page do not necessarily reflect the views of nor are they endorsed by the University of Georgia or the University System of Georgia.