The Origin of Iodine-129: By Physics or Fantasies?
Kevin R. Henke, Ph.D.
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Dalrymple (1991, p. 376f), James Moore and many others have argued that the absence of naturally occurring short-lived radioisotopes on Earth indicates that our planet is billions of years old rather than the 6,000 to 10,000 years as proclaimed by young-Earth creationists (YECs). In particular, Dalrymple (1991, p. 376-377) notes that there are 34 known radioisotopes with half-lives of greater than one million years. Only five radioisotopes with half-lives between one million and 80 million years are known to naturally regenerate on Earth, the Moon and/or in the space surrounding our planet. Specifically, nuclear physicists have determined that cosmic rays may produce 53Mn (half-life of 3.7 million years), 10Be (half-life of 1.6 million years), and 129I (half-life of 17 million years) (Dalrymple, 1991, p. 376-377). 129I may also form in terrestrial uranium-rich rocks from the spontaneous fission of 238U (Dalrymple, 1991, p. 376-377; Moran, 1996, p. 686). Slow neutrons interacting with uranium ores may generate 236U (half-life of 23.9 million years) (Dalrymple, 1991, p. 376-377). Although it is not known to naturally occur on Earth, cosmic rays produce 237Np (half-life of 2.14 million years) on the surface of the Moon (Dalrymple, 1991, p. 376-377). Otherwise, NO naturally occurring radioactive isotopes with half-lives between one million and 80 million years have been found in our Solar System (Dalrymple, 1991, p. 377). If the Earth is only 6,000 to 10,000 years old as YECs claim, where are these relatively short-lived radioisotopes, namely: 146Sm, 205Pb, 247Cm, 182Hf, 107Pd, 135Cs, 97Tc, 150Gd, 93Zr, 98Tc, and 154Dy?
Dalrymple (1991, p. 376) proposes three SCIENTIFIC hypotheses to explain the absence of these short-lived radioisotopes:
1. it's simply chance;
2. the stellar, supernovae and other processes that synthesize elements failed to produce these radioactive isotopes;
3. the Earth is ancient and these radioisotopes decayed away long ago.
Dalrymple (1991, p. 378) calculated the probability that a 10,000 year old Earth would have, by chance alone, all radioactive isotopes with half-lives greater than 80 million years and NO non-regenerated radioactive isotopes with half-lives between 1,000 and 80 million years. The probability is a remote one chance in 300,000,000,000,000!
Elements may be easily detected in stars by analyzing their radiation emission spectra. These procedures actually discovered helium in the Sun before it was found on Earth! While non-regenerated short-lived radioisotopes are absent from the Earth, Sun and Moon, they have been found forming in stars that are much more massive and/or violent than our Sun. For example, 97Tc, which only has a half-life of 2.6 million years, has been detected in some stars (Dalrymple, 1991, p. 380). Promethium (Pm) has also been found forming in stars. The longest half-life of a Pm isotope is only 18 years (Dalrymple, 1991, p. 380). Furthermore, Dalrymple (1991, p. 379-384) discusses in some detail the stellar nuclear reactions that can produce short-lived radioisotopes and how the stable daughter products of extinct short-lived radioisotopes have been found in meteorites and other samples. There is no doubt that short-lived radioisotopes are capable of forming in supernovae and dense stars and that at least some of them existed at one time in our Solar System. However, they don't currently appear in natural materials in and around the Earth. The only rational and scientific explanation is that the Earth is billions of years old.
The two terrestrial-occurring non-regenerating radioisotopes with the shortest half-lives are 235U (half life of 704 million years) and 244Pu (half life of only 82 million years). Although natural 244Pu was found, its concentration was so low that it was barely detected. Through extraordinary separation techniques, a total of 8 x 10-15 grams of 244Pu was extracted from 85 kilograms of molybdenum ore from a California mine (Dalrymple, 1991, p. 386). This is hardly abundant and much rarer than what we would expect if the Earth was only 6,000 to 10,000 years old. To be exact, Dalrymple (1991, p. 386) calculates that if the Earth were only one billion years old, 244Pu would be in high enough concentrations that it would be easily found. Furthermore, missing radioisotopes, such as 146Sm, should be easily detected if the Earth was one billion years old or younger (Dalrymple, 1991, p. 386).
The lack of short-lived radioisotopes and the presence of radioisotopes with longer half-lives are clearly consistent with a 4.6 billion year old Earth. They also completely refute any creationist claims for a "young" Earth. To explain away the absence of short-lived radioisotopes in terrestrial materials, some YECs might hide behind the old flimsy excuse that "God just made the Earth that way" or that for some reason "God arbitrarily sped up radioactive decay rates during the Creation, Fall and/or Flood, but not during the Crucifixion." In other words, they would just invoke ad hoc and irrational miracles and leave it at that. To his credit, YEC Woodmorappe (1999, p. 26) avoids invoking this anti-scientific "escape hatch". Although Woodmorappe (1999) includes citations of Dalrymple (1991), he (1999, p. 26) blatantly ignores Dalrymple's (1991, p. 376-387) discussions of radioisotopes and how they undermine young-Earth creationism. Instead of recognizing that both natural and artificial (e.g., Hou et al., 2003) processes may produce 129I, Woodmorappe (1999, p. 26) wants to believe that the well-understood nuclear physics of regenerated radioisotopes is only an "assumption". He also selectively cites Moran (1996) and suggests that the presence of 129I in 12 brines (very salty groundwaters) from the Anadarko Basin of Oklahoma, USA, is due to their "young" age rather than fissiogenic regeneration from 238U. Yet, Woodmorappe (1999) fails to mention the following statement by Moran (1996, p. 688), which supports a fissiogenic origin for 129I and undermines his YEC agenda:
The range in 129I/I ratios [for the Anadarko Basin brines] is 95 to 348 x 10-15, with no obvious correlation with depth or with I concentration. These ratios are among the lowest measured to date on natural materials, CONSISTENT with the assumption that these waters have been hydrologically isolated from the atmosphere FOR MORE THAN 100 m.y. [my emphasis]
By looking at the hydraulic properties and organic geochemistry of the subsurface rocks in the basin, Moran (1996, p. 685, 690-692) concluded that the relatively organic- and uranium-rich Woodford Shale was the probable source of the radioactive iodine.
YECs have yet to produce any evidence of non-regenerated, short-lived isotopes in the geologic record. Where are they if the Earth is only 6,000 to 10,000 years old? Why haven't they been found in some of the countless routine mass spectrometry and other analyses of rocks, sediments, soils and water that are run each day? With all of these detailed analyses, where are they? Again, the search for natural plutonium has been intense, yet only tiny amounts have been found. Why should this search be so difficult if the Earth is young? Clearly, Woodmorappe and other YECs need to find short-lived radioisotopes that cannot be attributed to natural regeneration, such as: 146Sm, 205Pb, 247Cm, 182Hf, 107Pd, 135Cs, 97Tc, 150Gd, 93Zr, 98Tc, or 154Dy. Until they do, there's no reason to take their farfetched religious claims seriously.
Dalrymple, G.B., 1991, The Age of the Earth, Stanford University Press, Stanford, California.
Hou, X.L., C.L. Fogh, J. Kucera, K.G. Andersson, H. Dahlgaard, and S.P. Nielsen, 2003, "Iodine-129 and Caesium-137 in Chernobyl Contaminated Soil and their Chemical Fractionation", Sci. Total Environ., v. 308, p. 97-109.
Moran, J.E., 1996, "Origin of Iodine in the Anadarko Basin, Oklahoma: An 129I Study", AAPG Bull., v. 80, n. 5, May, p. 685-694.
Woodmorappe, J., 1999, The Mythology of Modern Dating Methods, Institute for Creation Research, El Cajon, CA.