2:15 PM - 2:30 PM
[PPS07-13] Determination of chemical composition units on Mercury by the multivariate analysis using major element composition measured by MESSENGER XRS
Keywords:Mercury, chemical composition, multivariate analysis
On the surface of Mercury, volatile elements are more abundant compared to the Earth and Venus [Peplowski et al. 2012], suggesting that the planet has experienced the modification of surface materials caused by numerous impact events after its formation and volatile abundance is sensitive to the effect [Hyodo et al. 2017]. Two types of different materials are distributed on the surface of Mercury: endogenous material and exogenous material. Endogenous materials constituted the planet soon after its formation and were exposed to the surface by subsequent volcanic eruptions [e.g., Denevi et al. 2013]; Exogenous materials are those originally constituted the impactors and were brought to Mercury by late accretion. Thus, the understanding of chemical compositions requires a comparison with geological backgrounds that reflects the volcanic and impact history. However, a huge gap in spatial resolutions between chemical and geological data makes a detailed comparison difficult [e.g., Peplowski et al. 2012; Nittler et al. 2020]. This study aims to determine the chemical unit classification using multi-dimensional chemical composition data.
We analyzed major element ratios (Mg, Al, S, Ca, and Fe abundances normalized by Si abundance) acquired by MESSENGER XRS by the k-means clustering method and principal component analysis. The yielded cluster boundaries and PC1 are dominated by Mg/Si ratio, indicating that the chemical heterogeneity on the surface of Mercury is almost described by the variation of the Mg/Si ratio.
The chemical compositions of more than 3 compositional clusters cannot be reproduced by a linear mixture only of 2 end-member compositions. This suggests that chemical composition mainly characterized by Mg/Si has the potential to discriminate more than 3 different lithologies. Additionally, the positive correlation between Mg/Si ratio and the crater number density on the surface, which reflects the surface formation age, implies the relationship between the chemical variation of surface material, that volcanic deposits, and, furthermore, the temporal variation of the degree of partial melting in the mantle.
We analyzed major element ratios (Mg, Al, S, Ca, and Fe abundances normalized by Si abundance) acquired by MESSENGER XRS by the k-means clustering method and principal component analysis. The yielded cluster boundaries and PC1 are dominated by Mg/Si ratio, indicating that the chemical heterogeneity on the surface of Mercury is almost described by the variation of the Mg/Si ratio.
The chemical compositions of more than 3 compositional clusters cannot be reproduced by a linear mixture only of 2 end-member compositions. This suggests that chemical composition mainly characterized by Mg/Si has the potential to discriminate more than 3 different lithologies. Additionally, the positive correlation between Mg/Si ratio and the crater number density on the surface, which reflects the surface formation age, implies the relationship between the chemical variation of surface material, that volcanic deposits, and, furthermore, the temporal variation of the degree of partial melting in the mantle.