Asteroidal Satellites and the "Exploded Planet Hypothesis"

In "Dark Matter Missing Planets & New Comets" a new theory called the exploded planet hypothesis (eph) was introduced. One of its consequences was the realization that natural satellites of asteroids and comets are commonplace. The book was published before the discovery of Comet Shoemaker-Levy 9 which consisted of more than 20 individual members and before the Galileo spacecraft returned its images of asteroid Ida's moon Dactyl, the first confirmed "minor satellite".

Mainstream astronomy has attempted to explain minor satellites saying they form following a collision between bodies, such as two asteroids. Accordingly, it is possible for two fragments from the ensuing debris cloud to become coupled gravitationally in a mutual orbit. As for multiple comet nuclei we are expected to believe that the gentle tidal forces exerted by a planet are sufficient to break off relatively large chunks of material. Upon closer inspection these argument are found to be wanting.

In a collision, every fragment either escapes or falls back to the impact site. No sideways angular momentum needed for a stable orbit is produced. The mutual distance between any two escaping fragments increases faster than the radius of either gravitational sphere of influence, so they likewise can never become stably bound.

These fatal dynamical objections must be overcome to form stable moons. One way to do that is to have an explosion originating at the center of a planet instead of at the surface of an asteroid. Then many fragments tend to follow nearly parallel, only-slowly-diverging paths away from the planet. Meanwhile, the gravitational spheres of influence of the slower, larger fragments increase rapidly in radius because most of the planet's mass is soon beyond them. So all nearby debris becomes trapped in orbit around those larger fragments. Natural dynamical and collisional evolution eventually sort out this debris, concentrating much of it toward the equatorial plane and toward the synchronous orbit (i.e., toward maximum stability).

So when a large fragment of the exploded planet, such as Comet SL-9, comes too close to Jupiter, its orbiting debris cloud gets stripped off and spreads out along the main fragment's orbit. You no longer need to invoke tidal forces no stronger than blowing gently on a bit of cigar ash to break apart a comet nucleus probably several kilometers in diameter.

Actually, collisions and explosions are surprisingly different dynamically. Collisions cause fragments of both bodies to depart from near the point of impact. This is on the surface of the larger body even if that body is destroyed by the collision. An eph-type explosion originates at the center of the larger body. This results in three differences relevant to satellite formation:

• An impact causes the mutual separation of all fragments to increase linearly with distance traveled away from the impact. A central explosion of a planet-sized body allows many fragments originating far from the center to travel along nearly parallel trajectories with similar speeds that diverge much more slowly.
• In an impact, small fragments tend to leave first and travel fastest, with large fragments lagging behind. Both mutual separation and the radius of the gravitational sphere of influence of each increase linearly with distance traveled away from the impact site. By contrast, in a planetary explosion, small late-leaving fragments are being continually propelled past large early-leaving fragments, rapidly decreasing the exploded planet's mass interior to the large fragments. This accelerates the speed of increase of their sphere of influence above linear with distance traveled, and allows them to capture nearby debris.
• Impacts are almost exclusively destructive. A planetary explosion propels considerable trailing material into the larger fragments that left first, causing them to accrete some additional mass, and enlarge their spheres of influence faster, on the way out.

Gravitational captures from a collision event are nearly impossible. And two adjacent fragments are outside one another's sphere of influence (which is generally smaller than a fragment's own radius) while still in the parent body. When ejected by an impact, the spheres of influence grow linearly with distance from the center of the parent body. But the actual separation grows linearly with distance from the impact site near the surface of the parent body. Since the latter is always greater than or equal to the former, no two co-moving fragments can ever get inside each other's spheres of influence.

With the NEAR-Eros prediction I do not claim that one success "proves" that eph is a better model. But I do claim that it has demonstrated that it is a model worthy to be discussed comparatively by planetary scientists in the light of all new and existing evidence. Moreover, the eph has much to recommend it, not the least of which are:

• Eph eliminates the need for an "Oort cloud".
• Eph predictively explains all the principal statistical properties of new and old comet orbits.
• Eph easily explains why new and old comet physical behavior is so drastically different.
• Eph is the only model that correctly predicts the split comet relative velocity vs. solar distance power law.
• Eph explains why many properties of meteorites are ordinarily associated only with major planets, such as pre-impact micro-diamonds.
• Eph explains the young cosmic ray exposure ages of meteorites, and why we seldom see two-stage exposure ages.
• Eph provides the needed recent source for Earth-crossing asteroids.
• Eph is a natural explanation for "explosion signatures" in main asteroid belt orbital elements.
• Eph explains the distribution of black, carbonaceous material on the airless bodies of the solar system, most notably for Icarus.