Indeed, even as the experimental work for this report in Nature was underway, three scientists were preparing to contest my results on polonium halos in granites. Their report appeared in the June 22, 1973, issue of Science (Moazed et al. 1973). The following quote shows the nature of their objections:
We now report the results of a series of measurements made on polonium-type halos. Our measurements do not support the polonium halo hypothesis. We cannot definitely rule out the existence of polonium halos, but it appears that there is no evidence requiring, or even firmly suggesting, their existence. It was realized very early that their existence would cause apparently insuperable geological problems since the relevant polonium half-life is of the order of minutes. Polonium halos would require that the polonium atoms become part of the inclusion within minutes of the formation of the polonium and that in this very short time the polonium must be so far removed from the parent uranium mass that its presence or location is no longer evident. (Moazed et al. 1973, 1272—italics mine).
The issues had begun to focus. These scientists saw that polonium halos in granites presented "apparently insuperable geological problems" to the conventional view of earth history. To protect this view they suggested that polonium halos might not even exist, claiming instead they might just be uranium halos.
A later review of my work, "Mystery of the Radiohalos," Research Communications Network, aptly noted the futility of their effort to eliminate polonium halos from the granites:
In preparing my reply to the Moazed et al. report I spent months studying uranium and polonium halos, both in mica and in another mineral, fluorite. The Radiohalo Catalogue (see Contents) shows photographs of a variety of those halos. Fluorite sometimes occurs along with mica in the so-called granitic pegmatites—regions within granites where crystals of different minerals can be quite large (several feet long in certain instances). The polonium halos in fluorite are virtually identical to their counterparts in mica. Sometimes they occur along tiny cracks and fissures and sometimes in regions free from mineral defects. Polonium halos in fluorite in defect-free regions are significant because this mineral does not exhibit the perfect cleavage property of mica. Since no cleavages exist for uranium solutions to have flowed in a laminar fashion through fluorite crystals, this excludes the possibility that polonium halos in defect regions could have originated secondarily from uranium daughter radioactivity. This is the same conclusion reached earlier in this chapter when the origin of polonium halos in mica were investigated using alpha-recoil techniques.
A number of new experimental techniques were incorporated into my response to the 1973 report of Moazed et al. A variety of experimental results, obtained with particle accelerators and a scanning electron microscope equipped with x-ray fluorescence capabilities, formed the basis for unambiguously identifying three different types of polonium halos in granites. I elaborated on a new standard for halo-size measurements to show conclusively that polonium halos are easily distinguished from uranium halos by their ring structure. Electron-induced, x-ray fluorescence analysis of selected uranium and polonium halo centers confirmed this difference: the uranium halo centers showed considerable amounts of uranium and only a small amount of lead, whereas the Po halo centers showed only the lead.
I submitted the manuscript to Science detailing the results of these experiments. After some revision it was published in April 1974 (Gentry 1974; Appendix). It contains the following statements about an alternative framework of earth history:
I stated these implications plainly, thus inviting my scientific colleagues to challenge the evidence; however, no one responded to this report.
Earth Science Associates