The natural thermoluminescence of meteorites: II. Meteorite orbits and orbital evolution

Natural thermoluminescence (TL) data for 26 meteorites for which orbital elements have been estimated are reported. Calculations of equilibrium natural TL level in ordinary chondrites suggest that TL should be a sensitive indicator of perihelion. Meteorites with perihelia 5 krad) with significant scatter as a result of slight variations in dose rate (shielding) and albedo. The data presented here generally agree with the theory and suggest an effective dose rate of ≈3 rad/year for most meteorites. Comparison with cosmic ray exposure ages indicates that natural TL level is also partly related to exposure age. Meteorites with high (>20 Ma) exposure ages generally have a lower and more constrained (10–30 krad) range of natural TL than meteorites with ages 90 krad). We suggest that this reflects orbital evolution, since mature meteorite orbits evolve to lower perihelia. The data presented here confirm the earlier observations that only a very small proportion of meteorites have experienced orbits with low perihelia within the last 10 5 years. The data suggest that