5. Identify and evaluate concentrations of unusual or unexpected minerals.

Representative spinel-rich spectra (solid lines) from Sinus Aestuum at 3 different locations and temperatures and nearby background soils (dashed lines). Despite the thermal emission (see background soils), the spinel-rich deposits clearly have very strong 2 μm features a weak or absent 1 μm bands as is characteristic of spinel.

The spectral coverage of M³ allows us to observe the lunar surface at new wavelengths and therefore to literally see the Moon in a new light. Among the most surprising mineral deposits identified by M³ are concentrations of the mineral spinel. Spinel is an aluminum oxide known to exist in lunar rocks, but in very low abundances (a few percent) and is spectrally characterized by having a very strong 2 μm absorption feature and a weak or absent 1 μm absorption feature. M³ discovered a region in the center of the lunar nearside that is dominated by 2 µm bands. This area, Sinus Aestuum, contains numerous volcanic deposits formed from fire-fountaining that appear to be spinel-rich. Similar nearby volcanic deposits of Rima Bode do not contain spinel. Fire-fountains or pyroclastic volcanism is the same type of eruption that occurred in Iceland’s Eyjafjallajokul volcano in 2010.