Comparing cometary injection mechanisms. Comparing the supernova-comet theory to the superwave theory, we see that each propose differing modes of comet injection into the solar system. According to the Firestone-West scenario, the condensed cometary bodies and nebular material making up the remnant purported to enter the solar system received their energetic forward thrust 41,000 years ago from a supernova explosion and are in a coasting mode when they arrive. In their book, they propose a different comet injection mechanism 41,000 year ago when the gamma ray flash arrived. This one turns out to be very similar to the superwave comet injection mechanism that I had originated in 1983 and which was summarized in section 3 above (point number 2).
     In the superwave version, the superwave galactic cosmic rays would become trapped in the heliopause magnetic sheath as well as in its surrounding shock front region and would have built up to a sufficiently high energy density to have vaporized material from the surfaces of comets already in orbit about the Sun and those continually entering the solar system from the 2 million year old North Polar Spur supernova remnant. This vaporization process was theorized to fragment cometary bodies and nudge some of them into orbits that would cause them to pass into the inner solar system (LaViolette, 1983a, ch. 3-a); download chapter 3 excerpt. The influx of smaller-sized Tunguska-like cometary bodies would be far more common than comets several kilometers in diameter.
     Firestone, West, and Warwick-Smith (2006) propose a similar mechanism, except they replace the superwave cosmic rays with gamma radiation from their supernova explosion. They suggest that the arriving gamma radiation pulse vaporized material from comets orbiting the Sun and that the resulting gas jets would have nudged some of these comets into the inner solar system, increasing the risk of Earth impacts for a few thousand years. Since such comets would have entered at relatively low speeds, their 41 kyr b2k scenario avoids the problems inherent with the hypervelocity comet scenario discussed below. In my opinion they would be closer to the truth if they dispensed with the idea of hypervelocity supernova fragments and orbiting comets being vaporized by a supernova gamma ray flash and instead substituted superwave cosmic rays as the vaporizing agent.
     Problem 3: Unreasonably high comet kinetic energy. The contention that cometary material made a high-speed entry into the solar system 34,000 and 13,000 years ago creates serious problems for the supernova theory. A velocity of 2100 to 2700 km/s is about 100 times higher than the velocity estimated for the asteroid that caused the extinction of the dinosaurs. Since kinetic energy scales as v², this implies that each gram of matter in the Firestone-West comet carried 10,000 times as much kinetic energy as a gram of matter in the asteroid that impacted at the C/T boundary. As noted above, it would have been extremely unlikely that a comet even one kilometer in diameter would have collided with the Earth. But suppose that their comet had a diameter of 4 kilometers as Firestone and West have recently proposed. At this high speed the comet would have had 8 times the impact energy of the C/T boundary asteroid (given that the C/T asteroid had a diameter of 20 to 40 km and a density of 3 g/cc). This would have been the equivalent of 400,000 megatons of TNT.
     But, in their book they propose even larger comet impacts, several bodies being in the giant comet range with diameters ranging from 105 to 480 kilometers. Again disregarding the fact that such sizes would have been even less likely to have been supplied by an expanding supernova remnant, the impact energies now become outrageously large, each impact carrying between 10⁵ and 10⁷ the impact energy of the asteroid that caused the dinosaur extinction, or 10¹⁰ to 10¹² megatons of TNT. At these levels we are more in the realm of complete sterilization of the Earth's surface. If the energy of just one of the larger of these proposed impacts were spread evenly over the Earth's surface, it would dump about 5 X 10²⁷ joules into the Earth's atmosphere, or 100 calories into each cubic centimeter, raising the temperature of the Earth's atmosphere over 300,000 degrees Celsius and instantly turning it into a plasma. It would be a wonder that we would have any atmosphere at all left after that kind of impact. It is understandable then why Firestone and West have been quoting more modest comet sizes in their more recent press interviews.
     Problem 4: Not enough time for a comet to explode. The notion that the comet exploded in the atmosphere before it struck the Earth also encounters difficulty. If we assume that the comet entered at an angle of 25 degrees relative to the Earth's surface, its path length through the troposphere should have measured about 26 kilometers. If its entry speed was a few thousand km/s, this implies that it would have passed through the Earth's atmosphere to impact the ground in about 10 milliseconds! Surely this time is far too short for a comet to explode and aerially disperse its contents prior to reaching the Earth's surface. Also the shock wave created in the atmosphere by a comet impacting at almost one percent of the speed of light would have had to be enormous, again raising serious doubts.
     Problem 5: The hypervelocity vaporization problem. There is also the question as to how volatile metals and carbonaceous materials containing helium could have survived such a high impact energy without being entirely vaporized. It is likely for this reason that Darrah, et al. (2007) attribute the increased He-3 in the carbonaceous residues found in the boundary layer bulk sediment to an increase in the influx of interplanetary dust particles, i.e., material already existing in particle form in space and settling through the atmosphere at a more leisurely rate. As such, their interpretation more strongly supports the superwave cosmic dust theory than the Firestone-West comet explosion theory.
     The relativistic entry velocity issue becomes even more problematic in the case of the 34,000 year old mammoth tusk event. In 2005, Firestone and West proposed that iron rich grains had passed through the Earth's atmosphere at 10,000 km/s (3 percent of the speed of light) to create pits in the surface of 34,000 year old mammoth tusks. It is highly improbable that grains traveling at such a high velocity would have survived entry and reached ground level without totally vaporizing. Dust particles and meteoritic grains currently observed to travel at tens of kilometers per second usually burn up before reaching the ground leaving a trail of meteoric smoke. Only particles with low entrance velocities are able to make the journey to the ground intact. Indeed, this unusual claim of 10,000 km/s speeds has sparked serious criticism in internet astronomy discussion groups. Although blog comments do not carry the same weight as refereed publications, nevertheless, the correspondents bring up points very worthy of consideration. Regarding hypervelocity micrometeorites, one correspondent writes:

"If a particle enters the atmosphere at a [given] speed, pressure will build up at the front of this particle. The higher the speed, the higher the pressure. The higher the pressure, the higher is the temperature caused by the pressure, and the greater is the force working against that moving particle, and thus it is braking down the particle. If the pressure is too high, the resulting force can be too much for the structure of the particle to stand it, and then the particle breaks up... No particle which travels at a speed of 10000 km/s into the atmosphere will be able to reach the ground intact, and still be at this speed!
Günther: http://www.bautforum.com/archive/index.php/t-1180.html%3C/t-33032.html

   Another blog correspondent wonders whether the claim for 10,000 km/s arose because a reporter writing this story had misinterpreted the scientists' statements. He then exclaims:

"Grains" of iron simply cannot strike the surface of the Earth at high speed. It cannot happen."
http://www.unexplained-mysteries.com/forum/index.php?showtopic=52036

     Sadly, news reporters faithfully quoted this 10,000 km/s speed from the Lawrence Berkeley Laboratory press release issued on September 23, 2005. It is a pity that science news reporters do not more critically evaluate the veracity of ideas issued in press releases. Just because the press release comes from a "reputable" government institution does not necessarily mean that it is error free.
     So why would Firestone and West propose such a high speed for the supernova ejecta? Well, they need the speed to be this high so that their supernova blast wave theory is able to account for radiocarbon peaks dated at 41,000 and 34,000 years BP, as observed in Icelandic marine sediments. They proposed that the supernova occurred about 41,000 years ago and that its gamma ray flash arrived within a few hundred years to create the first C-14 peak at 41,000 years b2k peak. They then suggest that the supernova's condensed ejecta arrived 7000 years later to impact the mammoth tusks around 34 kyrs b2k and that this was accompanied by trapped cosmic rays which produced a second radiocarbon peak. Divide 250 light years (which is what they proposed for the distance to the supernova explosion center) by 7000 years of flight time and you get 10,700 km/s. Thus their contention of a relativistic iron grain volley arriving at 3% c was intended primarily as a "fit" to this Icelandic data, the 41,000 years b2k peak being attributed to gamma rays and cosmic rays from the initial supernova explosion and the 34,000 years b2k peak being attributed to the arrival of the supernova's relativistic ejecta. They then proposed the occurrence of an additional cometary impact event in order to offer an explanation for the 12,900 years y2k megafaunal extinction event. However, not only does this supernova model seem to be a forced fit to the geological record, it also appears to be quite implausible.
     This third radiocarbon increase at 13 kyrs b2k, they speculate, may have been produced by hypervelocity comets and debris from the supernova striking the Earth and injecting radiocarbon into the Earth's atmosphere. Their explanation here is a bit suspect since meteoric or cometary material would not contain radiocarbon in sufficient quantities to have an appreciable effect on the atmospheric radiocarbon levels. Furthermore as we shall see, there are more than just three radiocarbon increases that need explaining as well as numerous beryllium-10 peaks.