AN INVALUABLE LINK BETWEEN APOLLO AND THE NEXT GENERATION OF LUNATICS

A few samples collected on the lunar surface by Apollo astronauts were left unopened and kept for analysis by future generations. Chip Shearer has been tireless in campaigning to get these unopened samples made available for analysis and 50 years after the landing of Apollo 11, his dream became a reality.

The Apollo Next Generation Sample Analysis (ANGSA) opened 2 core tubes sealed on the Moon in 1972 by the Apollo 17 astronauts at Station 3 (samples 73001 & 73002). These sampled a landslide deposit into the Taurus Littrow valley from the South Massif (Schmitt et al. 2017, Icarus 298, 2-33, Fig. 4). Each core tube was first analyzed by XCT imagery to get an understanding of clast distribution and grain size variation. Our group was allocated 50 mg aliquots of fine-grained regolith material every 0.5 cm down the core tube to define the chemical stratigraphy. In addition, we used XCT imagery of the basalt clasts extracted from 73001 and 73002 to undertake crystal size distribution analyses, focusing initially on ilmenite and subsequently plagioclase. This textural study allowed comparison with other Apollo 17 basalts already analyzed (Donohue & Neal 2015, GCA 149, 115-130) and also highlighted any unique textural features in these new basalt samples. This allowed productivity during the pandemic when university labs were closed. In addition, this project also resulted in a follow on study using controlled cooling rate experiments on experimental charges of an Apollo 17 high-Ti basalt composition to texturally quantify cooling rates of these basalts. XCT imagery also allowed an examination of preferred crystal orientation; this technique represents an exciting new development in understanding textural development in igneous samples.

The chemical stratigraphy determined for the two cores shows subtle variations in major element composition demonstrating the well-mixed nature of the landslide deposit. However, certain horizons exhibit increases in incompatible trace element abundances suggesting a KREEP component is heterogeneously dispersed within the regolith column.

Finally, this project helped train and educate 3 of the next generation of lunar sample analysts, who are co-authors. This was only possible through the dogged determination of Chip Shearer to obtain permission to open these samples along with the funding to generate the results that will be presented here.