"Fact one: in your testimony, Professor Yardley, you indicated researchers have maintained there probably were 15-16 meteorite collisions with the Earth, occurring some time after 4.3 billion years ago. Furthermore, these collisions were projected to possess more force than the ones causing the largest lunar crater Imbrium.

"Fact two: the magnitude of these events would be sufficient, at the higher level, to vaporize the ocean, or, at the lower level, to vaporize the photic zone.

"Fact three: these collisions were believed to have occurred somewhere between 4.3 and 3.8 billion years ago.

"Fact four: these events were stochastically distributed across a 500 million year interval.

"Fact five: the first indirect, potential evidence for the existence of life is dated around 3.85 billion years ago.

"Fact six: the first, direct fossil evidence for the existence of life is dated from about 3.55 billion years ago.

"Fact seven: an event intermediate between a collision that would have vaporized the ocean and one which would have vaporized the photic zone occurred approximately 65 million years ago.

"My questions to you Dr. Yardley are these: One, given the foregoing facts, when, precisely, during the interval between, say, 4.3 billion years ago and 3.55 billion years ago, did the 15-16 projected collisions with Earth occur?

"Two, given the foregoing facts, is one justified in treating the event which took place 65 million years ago, as part of the stochastic distribution of the original 15-16 events?"

Dr. Yardley looked at Mr. Tappin, apparently considering the questions. The professor started to speak and, then, stopped.

Finally, he said: "There really is no way, at the present time, to answer your first question with any precision. As far as the second question is concerned, I'm not sure the Yucatan crater should be considered as part of the original stochastic distribution profile.

"I suppose, nonetheless, a case might be made by some individuals to include, on justifiable grounds, the Yucatan event in the original stochastic distribution. The object which collided with Earth some 65 million years ago may well have been a remnant of the original debris that had been bombarding the Earth during the Archean era and on which the projected 15-16 collisions is based."

"Would you agree, then, Dr. Yardley," inquired the defense lawyer, "that, on the basis of the available evidence, someone who claimed the last ocean-vaporizing collision took place 3.73 billion years ago would be as justified in her or his claim as the person who claimed the last ocean-vaporizing collision took place 3.54 billion years ago - or, even, for that matter, in claiming that an ocean vaporizing incident occurred tens of thousands of years after the period which has been established empirically for the earliest evidence of life on Earth?"

"Yes and no," replied the professor. When Dr. Yardley realized Mr. Tappin was waiting for the answer to be expanded on, the professor said: "I agree, reluctantly, with your basic point about the unknown nature of the historical time which was actually available to be able to go from prebiotic conditions to biological organisms through natural processes.

"On the other hand," the professor added, "if the Isau sample does have biological origins, then the person who claimed the last ocean-vaporizing event took place 3.54 billion years ago is somewhat in conflict with the facts because of the evidence for the existence of life at both 3.85 billion years ago, as well as 3.55 billion years ago. Seemingly, a continuity of some sort has been established through the two kinds of dated evidence for the existence of life at Isau and Warrawoona."

"Isn't it conceivable," asked Mr. Tappin, "that life may have originated more than once? After all, Professor, in your direct testimony you spoke about the possibility of protocells and organisms existing in the early Archean era which were not part of the lineage that is linked, in any way, with the last common ancestor of all modern forms of life. Were you not suggesting, during your testimony, that life could have arisen, in various forms, more than once?"

"Yes," Dr. Yardley acknowledged, "I was suggesting this. However, the fossil evidence discovered at the 3.55 billion year old Warrawoona Group contains the imprints of eleven different kinds of microorganisms. One would be asking a lot to suppose this much diversity could arise so quickly after an ocean-vaporizing event of the sort you have hypothesized."

"I agree with you," confirmed Mr. Tappin. "Such a scenario may be stretching things to the point of snapping, but this is not my problem, Professor, it is yours.

"More specifically, Dr Yardley, if one cannot establish beyond any reasonable doubt as to when the last photic zone destroying collision took place or when the last ocean-vaporizing event occurred, then all evolution theorists are doing is playing with some numbers in a way that creates the illusion of lending factual support to their own belief in evolutionary theory. In reality, however, they merely are assuming their conclusions - is this not the case, Professor?"

At this point, the prosecuting lawyer objected with: "Your Honor, the question is argumentative."

"Counsel's objection is sustained," ruled Judge Arnsberger. "Rephrase the question, Mr. Tappin."

The lawyer for the defense replied: "I'll withdraw the question, your Honor," and, then, with barely a pause, he pressed on but in a different direction. "Dr. Yardley," Mr. Tappin asked, "are you familiar with the so-called 'faint young sun paradox'?"

"Yes, I am," responded the professor.

"Would you explain to the court the nature of this paradox?" Mr. Tappin requested.

"On the basis of various calculations performed by astronomers, many scientists accept, as likely, that 4 billion years ago, the sun actually was some 25-30 percent dimmer than today. If this is so, then a possible paradox emerges.

"More specifically, considered in terms of the current atmospheric conditions of the world, if the sun were 25-30 percent dimmer than is presently the case, then the upper 300 meters of the ocean would freeze, along with rivers, lakes and inland seas. In addition, under these circumstances, the ice sheet covering the Earth would reflect much of the rest of the sun's incoming light, thereby preventing any thawing from taking place.

"Evidence, on the other hand, derived from a variety of sedimentary rocks indicates liquid water was in existence around 3.8 billion years ago. Furthermore, direct fossil evidence demonstrates the existence of biological organisms as early as 3.55 billion years ago.

"The paradox is as follows. How could liquid water and biological organisms exist in environmental conditions which should have been frozen due to the presence of a faint young sun?"

"Is it not possible," inquired Mr. Tappin, "that various combinations of hydrothermal vents, volcanic islands, and so on, in different parts of the Earth, could have generated a set of relatively localized conditions capable of, over time, producing both sedimentary rocks as well as sustaining life forms?"

Professor Yardley shrugged his shoulders. His face had an expression which seemed to be a blend both of skepticism as well as a considering of possibilities in relation to the defense attorney's suggestion.

The professor's head bobbed back and forth slightly, and he appeared to be weighing things in his mind. Finally, he said: "Maybe, but researchers have come up with a number of other possibilities."

"Would you outline a few of these possibilities?" requested the defense attorney.

"Since astronomers calculate the early sun probably would not have overcome its faintness until around 2.5 billion years ago," Dr. Yardley began, "the challenge is to devise ways capable of permitting the Earth to compensate for the sun's relative dimness during the Archean era. The ways which have been devised concern conjectures about the compositional character of the paleoatmosphere - that is, the Earth's early atmosphere.

"For example, during the 1970s, there were several attempts to resolve the faint early sun paradox. The first proposal focused on methane and ammonia, while a second suggestion concerned carbon dioxide.

"Ammonia and methane both absorb, and, therefore, trap, certain portions of the infrared spectrum which is being produced by the Earth as the planet is heated by solar radiation. The absorbed infrared energy heats up the atmosphere, and the atmosphere, in turn, begins to radiate infrared wave lengths, some of which return to the Earth's surface in the form of what many people have referred to as the 'greenhouse effect';.

"If there were enough methane and ammonia in the atmosphere, then considerable amounts of infrared energy would be absorbed and, eventually, radiated back to the Earth. In fact, some researchers believe this process might have been able to generate and radiate sufficient heat back to the Earth's surface to compensate for the faint early sun.

"There are, however, several problems with the methane/ammonia compensation hypothesis. To begin with, both methane and ammonia are susceptible, in varying degrees, to photolytic dissociation, or breakdown, as a result of the effect of ultraviolet radiation.

"Moreover, both methane and ammonia tend to enter into reactions with the hydroxyl radical [OH] which arises as a result of the photolysis, or breakdown by ultraviolet radiation, of H₂O. While some of these hydroxyl radicals would combine with the hydrogen gas coming from volcanic emissions, enough free hydroxyl radicals still may have been available for chemical reaction with a great deal of methane and ammonia, and, consequently, removed these molecules from the atmosphere.

"In addition, ammonia is quite soluble in water. Therefore, NH₃ tends to be lost from the atmosphere through rainout.

"There have been some studies indicating that the presence of protective buffers, such as water vapor in the case of methane, and hydrogen sulfide in the case of ammonia, can affect the rates and extent of photo destruction of methane and ammonia. Furthermore, another study suggested the photolysis of methane could produce several hydrocarbons, such as hydrogen gas and methylene (CH₂), which are efficient absorbers of infrared radiation.

"Despite this sort of data, the overall effect of photolysis, chemical reactions and rainout, likely would have resulted in the removal of most of the methane and ammonia molecules which may have been present, at some point, in the Archean atmosphere. Therefore, an atmosphere composed largely of methane and ammonia would not have had a very long lifetime unless there were some continuous source of production for these molecules.

"Today's atmosphere consists of a mixing ratio of about 1 part per billion of ammonia, as well as 1.6 parts per million of methane. The presence of these molecules in our atmosphere is entirely the result of biogenic production.

"Once the Earth had differentiated, through the formation of the magnetic core, and, in the process, removed much of the Earth's iron from the surface, there would have been no chemical mechanism on prebiotic Earth, of which I am aware, capable of producing, on a continuous basis, either ammonia or methane. Thus, these molecules wouldn't be able to solve the faint early sun paradox."

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