The natural thermoluminescence of Antarctic meteorites and their terrestrial ages and orbits: A 2010 update

Abstract

Abstract-We have examined the relationship between natural thermoluminescence (TL) and 26 Al in 120 Antarctic meteorites in order to explore the orbital history and terrestrial ages of these meteorites. Our results confirm the observations of Hasan et al. (1987) which were based on 23 meteorites. For most meteorites there was a positive correlation between natural TL and 26 Al, reflecting their similarity in decay rate under Antarctic conditions and thus in terrestrial age. For a small group with low TL and high 26 Al a small perihelion was proposed. Within this group, natural TL decreases with terrestrial age as determined by 36 Cl measurements, although the rate of TL decay is faster (half-life approximately 10 ka) and the ages that can be determined are smaller (<200 ka) than for most meteorites. The faster decay rate and lower natural TL levels are a reflection of recent exposure to higher radiation doses and higher temperatures, since this history would populate less stable TL traps with smaller electron densities. We sort the 120 meteorites by perihelion and terrestrial age. The normal perihelion group range up to approximately 1000 ka and the small perihelion group range up to approximately 200 ka. An intermediate perihelion group tends to have short terrestrial ages (20-60 ka). There is acceptable agreement between most (34 out of 43) of our present terrestrial age estimates and those determined by isotopic means, the exceptions reflecting complex irradiation histories, long burial times in the Antarctic, or other issues.

The thermoluminescence of meteorites: A brief 2010 perspective

“…Variation in the TL levels of recently fallen meteorites is primarily due to differences in orbit (Melcher, 1981b;McKeever and Sears, 1980;Benoit et al, 1991;. In fact, the distribution of natural TL levels for recent falls is very similar to the distribution of perihelia observed for near Earth asteroids with the majority having perihelia of 0.8-1.0 AU (Sears et al, 2011). This is also true of the ordinary chondrite meteorites with known orbits.…”

The Sutter's Mill meteorite: Thermoluminescence data on thermal and metamorphic history

“…, , ; Benoit and Sears ; Sears et al. ). The perihelion of the orbit of Sutter's Mill was 0.448 ± 0.024 AU for which the calculated temperature is 346 ± 5 °C (e.g., McKeever and Sears ).…”

“…3, McKeever and Sears (1980) suggested that Olivenza (LL5) and Mangwendi (LL6) had small perihelia, say <0.6 AU. In fact, in every independent database assembled (observed falls, non-Antarctic finds, Antarctic finds, basaltic meteorites, and so on), about 20% have natural TL values suggestive of similarly small perihelia (Hasan et al 1987;Benoit et al 1992Benoit et al , 1994Sears et al 2011). The perihelion of the orbit of Sutter's Mill was 0.448 AE 0.024 AU for which the calculated temperature is 346 AE 5°C (e.g., McKeever and Sears 1980).…”