Hazards from comets and asteroids

The first angel sounded his trumpet, and there came hail and fire mixed with blood, and it was hurled down upon the earth. A third of the earth was burned up, a third of the trees were burned up, and all the green grass was burned up. The second angel sounded his trumpet, and something like a huge mountain, all ablaze, was thrown into the sea . . . The third angel sounded his trumpet, and a great star, blazing like a torch, fell from the sky on a third of the rivers . . . a third of the sun was struck, a third of the moon, and a third of the stars, so that a third of them turned dark . . . and I saw a star that had fallen from the sky to the earth. The star was given the key to the shaft of the Abyss. When he opened the Abyss, smoke rose from it like the smoke from a gigantic furnace. The sun and sky were darkened by the smoke from the Abyss . . .. The Revelation of St John was probably written around 100 ad, but is part of a very much older ‘Star Wars’ literature, going back to the very earliest writings and probably based on pre-literate oral traditions. Common threads in these tales are often hot blast, hurricane winds, flattened forests, tsunami and cataclysmic floods, associated with blazing thunderbolts from the sky, a darkened sun, a great, red-tailed comet and what appears to be a meteor storm. Even without benefit of the twentieth century Tunguska impact, which destroyed 2000 square kilometres of Siberian forest in 1908, classical scholars have long regarded the stories as descriptions of a cosmic impact. Myth was a vehicle for transmitting astronomical and cosmological information through the generations, and it is surely a seductive proposition to see these tales of celestial catastrophe – which are found worldwide – as prehistoric descriptions of cosmic cataclysm, one-off or recurrent, local or global. Inevitably, this is a contentious area – only qualitative statements can be made, and one individual’s unifying hypothesis is another’s Velikovskian fantasy.

The challenge of the exploded planet hypothesis

The hypothesis of the explosion of a number of planets and moons of our Solar System during its 4.6-billion-year history is in excellent accord with all known observational constraints, even without adjustable parameters or ad hoc helper hypotheses. Many of its boldest predictions have been fulfilled. In most instances, these predictions were judged highly unlikely by the current standard models. Moreover, in several cases, the entire exploded planet model was at risk of being falsified if the predictions failed. The successful predictions include: (1) satellites of asteroids; (2) satellites of comets; (3) salt water in meteorites; (4) ‘roll marks’ leading to boulders on asteroids; (5) the time and peak rate of the 1999 Leonid meteor storm; (6) explosion signatures for asteroids; (7) the strongly spiked energy parameter for new comets; (8) the distribution of black material on slowly rotating airless bodies; (9) splitting velocities of comets; (10) the asteroid-like nature of Deep Impact target Comet Tempel 1; and (11) the presence of high-formation-temperature minerals in the Stardust comet dust sample return. In physics and astronomy, hypotheses are either falsified if their predictions fail, or proved to be of value if they succeed. By all existing evidence, the exploded planet hypothesis has proved far more useful than the half-dozen or so hypotheses it would replace. Among the many important corollaries are these. (a) Perhaps as many as six former planets of our Solar System have exploded over its 4.6-billion-year history. (b) In particular, Mars is not an original planet, but a former moon of an exploded planet. (c) As a major player in Solar System evolution, the exploded planet scenario must be considered as a likely propagation vehicle for the spread of biogenic organisms. We conclude with a brief mention of three possible planetary explosion mechanisms.