Did More Than One Planet Explode?

Many lines of evidence suggest more than one planetary explosion in the solar system’s history. The discovery of one, and probably two, new asteroid belts orbiting the Sun beyond Neptune is especially suggestive, given that the main asteroid belt is apparently of exploded planet origin. Evidence of the “late heavy bombardment” in the early solar system is another strong indicator. These points are discussed later in this article.

On Earth, geological boundaries are accompanied by mass extinctions at five epochs over the last billion years. Two of the most intense of these, the P/T boundary about 250 Mya, and the K/T boundary (and the extinction of dinosaurs) at 65 Mya, are the most likely to be associated with the damage to Earth’s biosphere we would expect from a major planet explosion.

Meteorites provide direct evidence about their parent bodies. Yet this evidence strongly indicates at least 3-4 distinct parent bodies. Oxygen isotope ratios are generally similar for related planetary bodies, such as all native Earth and Moon rocks. These ratios for meteorites imply at least two distinct, unrelated parent bodies, and probably more. Cosmic ray exposure ages of meteorites indicate how long these bodies have been exposed to space, because cosmic rays can penetrate only about a meter into a solid body. Collisional break-up can reset the exposure ages for some meteorites, and produce “double exposure” or other complexities for others. The data show clustering of exposure ages around several different primary epochs, suggesting multiple explosion epochs.

Main belt asteroids come in many types, but most of these represent sub-types of the two major types: 80% of all main belt asteroids are of type C (“carbonaceous”), and most of the remaining 20% are of type S (“silicaceous”). The former are found predominately in the middle and outer belt, while the latter are mostly in the inner belt, the part that lies closest to Mars. These two types are unlikely to have had the same parent body.

Finally, it should be noted that we can estimate the total mass of the body that exploded to produce all the comets seen today. (The lifetime of those comets is limited to 10 million years by galactic tidal forces and planetary perturbations.) That parent body mass is almost certainly less than the size of our Moon because the carbonaceous meteorites most closely associated with comets indicate a parent body too small to have been chemically differentiated by gravity (heavy elements to core, light elements to surface).