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Space weathering alters the surface materials of airless planetary bodies; however, the effects on moderately volatile elements in the lunar regolith are not well constrained. For the first time, we provide depth profiles for stable K and Fe isotopes in a continuous lunar regolith core, Apollo 17 double drive tube 73001/2. The top of the core is enriched in heavy K isotopes (delta 41K = 3.48 +/- 0.05 parts per thousand) with a significant trend toward lighter K isotopes to a depth of 7 cm; while the lower 44 cm has only slight variation with an average delta 41K value of 0.15 +/- 0.05 parts per thousand. Iron, which is more refractory, shows only minor variation; the delta 56Fe value at the top of the core is 0.16 +/- 0.02 parts per thousand while the average bottom 44 cm is 0.11 +/- 0.03 parts per thousand. The isotopic fractionation in the top 7 cm of the core, especially the K isotopes, correlates with soil maturity as measured by ferromagnetic resonance. Kinetic fractionation from volatilization by micrometeoroid impacts is modeled in the double drive tube 73001/2 using Rayleigh fractionation and can explain the observed K and Fe isotopic fractionation. Effects from cosmogenic 41K (from decay of 41Ca) were calculated and found to be negligible in 73001/2. In future sample return missions, researchers can use heavy K isotope signatures as tracers of space weathering effects.

来源平台：JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS