Journal of Geophysical Research: Planets
Mineralogical Diversity and Geology of Humboldt Crater
Derived Using Moon Mineralogy Mapper Data
, S. Besse
, J. Flahaut
, C. Quantin-Nataf
, L. Lozac’h
and W. van Westrenen
Faculty of Science, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands,
Université Lyon 1, ENS-Lyon, CNRS, UMR
5276 LGL-TPE, Villeurbanne, France,
European Space Astronomy Centre, Madrid, Spain,
Institut de Recherche en
Astrophysique et Planétologie, CNRS/UMR 5277, Université Paul Sabatier, Toulouse, France
Moon Mineralogy Mapper (M
) spectroscopic data and high-resolution imagery data sets
were used to study the mineralogy and geology of the 207 km diameter Humboldt crater. Analyses of M
data, using a custom-made method for M
spectra continuum removal and spectral parameters calculation,
reveal multiple pure crystalline plagioclase detections within the Humboldt crater central peak complex,
hinting at its crustal origin. However, olivine, spinel, and glass are observed in the crater walls and rims,
suggesting these minerals derive from shallower levels than the plagioclase of the central peak complex.
High-calcium pyroxenes are detected in association with volcanic deposits emplaced on the crater’s ﬂoor.
Geologic mapping was performed, and the age of Humboldt crater’s units was estimated from crater counts.
Results suggest that volcanic activity within this ﬂoor-fractured crater spanned over a billion years. The felsic
mineralogy of the central peak complex region, which presumably excavated deeper material, and the
shallow maﬁc minerals (olivine and spinel) detected in Humboldt crater walls and rim are not in accordance
with the general view of the structure of the lunar crust. Our observations can be explained by the presence
of a maﬁc pluton emplaced in the anorthositic crust prior to the Humboldt-forming impact event.
Alternatively, the excavation of Australe basin ejecta could explain the observed mineralogical detections.
This highlights the importance of detailed combined mineralogical and geological remote sensing studies
to assess the heterogeneity of the lunar crust.
Plain Language Summary
Humboldt crater is a 207 km diameter complex impact crater located
on the farside of the Moon. A central peak sits in its center, whereas its periphery is occupied by volcanic
deposits. The peak was formed during the crater-forming impact event, as material from depth was brought
up to the surface. In this study, we make use of the light that is reﬂected from the lunar surface to infer
its composition. We used data from the Moon Mineralogy Mapper (M
) instrument, a visible near-infrared
spectrometer, that orbited the Moon between 2008 and 2009. We surveyed the mineralogy of the diﬀerent
crater units and dated them by crater counts. We found that volcanic activity in Humboldt crater might have
spanned over 1 Ga. Plagioclase minerals detected in the Humboldt crater central peak hints at its crustal
origin, whereas the mineralogic assemblage of the crater walls and rim is more puzzling and raises questions
about the lunar crust structure.
Studies of the structure of the lunar crust are important to constrain the magmatic and thermal evolution of
the Moon (e.g., Shearer et al., 2006). The Lunar Magma Ocean (LMO) concept predicts that the upper part of
the lunar crust was formed by ﬂoatation of plagioclase on a magma ocean, forming a
anorthositic upper crust (e.g., Kaula, 1979; Warren, 1985). Denser minerals formed during the earlier stages of
magma ocean crystallization (such as olivine and pyroxene) sank to the bottom the magma ocean, forming
the lower crust and mantle (e.g., Lin et al., 2017; Snyder et al., 1992).
A diversity of studies using diﬀerent remote sensing data have been conducted in order to establish a lunar
crustal stratigraphy. Many of these focus on the mineralogical composition of the central uplift of impact
craters, where material originating from greater depths is exposed (Cintala & Grieve, 1998). Scaling laws exist
to estimate the depth of origin of central uplift material, which is a function of the crater’s diameter (e.g.,
Cintala & Grieve, 1998; Melosh, 1989). Tompkins & Pieters (1999) studied the mineralogy of lunar crater’s
• Multiple pure crystalline plagioclase
are detected in the Humboldt crater
central peak complex, hinting at its
• Olivine, spinel, and glass are
detected in the crater’s walls and rim,
suggesting their shallow origin,
possibly linked to a plutonic event
• Crater counts performed on the
crater volcanic deposits suggest that
volcanic activity in Humboldt crater
spanned over a billion years
• Supporting Information S1
Martinot, M., Besse, S., Flahaut, J.,
Quantin-Nataf, C., Lozac’h, L.,
& van Westrenen, W. (2018).
Mineralogical diversity and geology
of Humboldt crater derived
using Moon Mineralogy Mapper
data. Journal of Geophysical
Research: Planets, 123, 612–629.
Received 4 SEP 2017
Accepted 20 NOV 2017
Accepted article online 21 DEC 2017
Published online 26 FEB 2018
©2017. The Authors.
This is an open access article under the
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License, which permits use and
distribution in any medium, provided
the original work is properly cited, the
use is non-commercial and no
modiﬁcations or adaptations are made.
MARTINOT ET AL. HUMBOLDT CRATER MINERALOGY AND GEOLOGY