Surkov and Fedoseyev reported in 1978 that in using data from the Mare Crisium region of the Moon recently explored by Luna 24, the reliability of forecasting the composition of surface rocks by remote-control methods is estimated. To determine more accurately the radioactivity distribution pattern across the surface of Mare Crisium, a comparison was made between the orbital and laboratory evaluations of the radioelement content in the regolith of this region. The data on the distribution of radioelements in the soil column brought from Mare Crisium were analyzed within the framework of Th-U and K-U systematics of lunar rocks in the light of the possible regolith formation processes at the Luna 24 landing site.
The authors concluded that it is interesting to compare once again the values of the average values of U and K characterizing the interior of the earth and the Moon. In one of the authors' papers dealing with a gamma-spectrometric analysis of lunar soil from the Luna 16 column (Surkov et al., 1972), they concluded that there is a similarity between average K/U ratios (about 2.8x103) for the earth and the Moon on the whole, evidence for the kinship of their primary non-differentiated matter. However, the calculated values of the overall uranium and potassium content on these neighboring celestial bodies seemed to differ considerably. That is why hypotheses were put forward to the effect that the lunar body could form in an independent circumsolar orbit with its subsequent capture by the Earth. In further estimates of the average potassium and uranium content on the Moon obtained by various methods, as new information came in, there were trends towards reducing the supposed level of these average contents, and the latest data for K of about 100 ppm (Taylor, 1977) to 140 ppm and U of about 0.020 ppm (Hubbard and Minear, 1976) to 0.050 ppm are considerably lower than the initial data (K of about 250 ppm and U of about 86 ppm).
The authors stated at the time that the coincidence of K/U ratios and, as is evident, is a very close similarity to the values of the average bulk potassium and uranium content in the Earth and the Moon. In its turn, this seems to testify quite convincingly in the authors' opinion to the genetic kinship of the matter which formed these two planetary bodies in the course of accretion. This parental matter was equally enriched (by three or four times) by refractory elements and depleted (about four-fold) as far as volatile elements are concerned with respect to the matter of carbonaceous chondrites (Cl).
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