The distribution of neutrons with energies below 15 MeV in spherical stony meteoroids is calculated using the ANISN neutron‐transport code. The source distributions and intensities of neutrons are calculated using cross sections for the production of tritium. The meteoroid's radius and chemical composition strongly influence the total neutron flux and the neutron energy spectrum, whereas the location within a meteoroid only affects the relative neutron intensities. Meteoroids must have radii of more than 50 g/cm2 before they have appreciable fluxes of neutrons near thermal energies. Meteoroids with high hydrogen or low iron contents can thermalize neutrons better than chondrites can. Rates for the production of 60Co, 59Ni, and 36Cl are calculated with these neutron fluxes and evaluated neutron‐capture cross sections and are reported for carbonaceous chondrites with high hydrogen contents, L‐chondrites, and aubrites. For most meteoroids with radii <300 g/cm2, the production rates of these neutron‐capture nuclides increase monotonically with depth. The highest calculated 60Co production rate in an ordinary chondrite is 375 atoms/min/g‐Co at the center of a meteoroid with a 250 g/cm2 radius. The production rates calculated for spallogenic 60Co and 59Ni are greater than the neutron‐capture rates for radii less than ∼50–75 g/cm2. Only for very large meteorpids and chlorine‐rich samples is the neutron‐capture production of 36Cl important. The results of these calculations are compared with those of previous calculations and with measured activities in many meteorites.
The interaction of both the particle and photon component of the solar wind with the lunar surface material is expected to produce diverse chemical reactions. Experimental evidence for proton-induced OH formation was obtained by bombarding a glass, chemically similar in composition to common silicate minerals, with high-energy protons. The concentration of OH, before and after irradiation, was determined by infrared absorption measurements. The OH formation rate was greatest at the start of the bombardment and decreased with increasing dose. The maximum proton to OH conversion rate, at the start of the irradiation, is at least 5 or 10% and may be as high as 100%. Using this result, together with estimates of the lunar age and recent solar proton flux data, we were able to make very rough calculations of the minimum proton-induced OH content in the lunar surface. If mixing or churning is not important, the upper centimeter could contain 4 X 10 •6 OH per cm 8. When protons below 40 Mev and the higher conversion rate are included in the computation, the estimated OH concentrations could increase by a factor of 10 or more. If surface mixing or churning has occurred, they should be divided by an average churning depth.
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