Unravelling similarities between Mount Etna's pyroclastic deposits and the Lunar counterparts.

In the last few years, NASA, ESA, CNSA and JAXA have been planning comprehensive lunar initiatives, including the Artemis program. In this context, it is crucial to i) support scientific research aimed at improving our ability to collect direct ground-truth data and samples, and ii) test equipment and validate analytical methodologies at designated analogue sites. Among the sites of interest on the lunar surface are the ones dominated by pyroclastic deposits since, as shown on Apollo samples, they may have trapped considerable volumes of gases³, being their formation linked to the presence of volatiles within magma. This material represent an intriguing in-situ resource¹ that has yet to be verified even considering studies on Earth analogues on volcanic environments. Some of them are well internationally-known (e.g., Lanzarote, Canary Islands⁴; Kilauea Volcano, USA; Lava Beds National Monument, USA)  and have been extensively studied. In other cases, such as Mount Etna, the compositional similarity remains unexplored, despite the site has already attracted interest from the planetary science community². Mount Etna volcano exhibits several geological similarities with lunar features such as the presence of  lava tubes, cinder cones, lava channels and bowl shaped pits; however, its analogy from a compositional point of view has yet to be determined.

For this reason, several unweathered and unaltered  samples have been collected from a pyroclastic deposit in the area of the Cisternazza pit crater, a collapse pit located on the southern flank of Mount Etna. The samples underwent comprehensive chemical and mineralogical characterization, revealing compositional similarities with lunar samples. Consequently, further tests were conducted to examine their mechanical, thermal, and spectral behaviour to compare it with lunar samples and certified lunar simulants across a broader range of properties.

To assess the analogy with the lunar surface, specific spectral parameters were also calculated for both the Etna samples and key sites on the Moon. In addition, in order to resemble the complex spectral response of the lunar pyroclastic deposits, we generated different mixtures using the spectra of the Etna samples intermixed with different amounts of olivine, orthopyroxene, and clinopyroxene endmembers spectra. Intriguing correlations between these mixtures and lunar spectral data were observed, even in study areas far from Apollo landing sites, indicating a broader range of similarities with the lunar pyroclastic materials.

Acknowledgement

This study was carried out within the Space It Up project funded by the Italian Space Agency, ASI, and the Ministry of University and Research, MUR, under contract n. 2024-5-E.0 - CUP n. I53D24000060005.

References

1: Anand et al., 2012, A brief review of chemical and mineralogical resources on the Moon and likely initial in situ resource utilization (ISRU) applications. Planet. Space Sci. 74, 42–48.

2: Carey et al., 2022, METERON Analog-1: A Touch Remote. 73rd International Astronautical Congress (IAC), Paris, France, 18–22 September 2022

3: Ivanov, 2014, Volatiles in lunar regolith samples: A survey. Sol. Syst. Res. 48, 113–129.

4: Mateo et al., 2019, Lanzarote and Chinijo Islands Geopark:From Earth to Space. Springer International Publishing.