Earth and Planetary Science Letters 420 (2015) 95–101
Contents lists available at ScienceDirect
Earth and Planetary Science Letters
www.elsevier.com/locate/epsl
Multiple origins for olivine at Copernicus crater
Deepak Dhingra ∗ , Carle M. Pieters, James W. Head
Earth, Environmental and Planetary Sciences, Brown University, Brook Street, Box 1846, Providence, RI 02912, USA
a r t i c l e
i n f o
Article history:
Received 4 August 2014
Received in revised form 17 February 2015
Accepted 24 March 2015
Available online xxxx
Editor: C. Sotin
Keywords:
impact melt
olivine
Copernicus crater
reflectance spectroscopy
Moon
Moon Mineralogy Mapper
a b s t r a c t
Multiple origins for olivine-bearing lithologies at Copernicus crater are recognized based on integrated
analysis of data from Chandrayaan-1 Moon Mineralogy Mapper (M3 ), Lunar Reconnaissance Orbiter (LRO)
Narrow Angle Camera (NAC) and Kaguya Terrain Camera (TC). We report the diverse morphological and
spectral character of previously known olivine-bearing exposures as well as the new olivine occurrences
identified in this study. Prominent albedo differences exist between olivine-bearing exposures in the
central peaks and a northern wall unit (the latter being ∼40% darker). The low-albedo wall unit occurs
as a linear mantling deposit and is interpreted to be of impact melt origin, in contrast with the largely
unmodified nature of olivine-bearing peaks. Small and localized occurrences of olivine-bearing lithology
have also been identified on the impact melt-rich floor, representing a third geologic setting (apart from
crater wall and peaks). Recent remote sensing missions have identified olivine-bearing exposures around
lunar basins (e.g. Yamamoto et al., 2010; Pieters et al., 2011; Kramer et al., 2013) and at other craters
(e.g. Sun and Li, 2014), renewing strong interest in its origin and provenance. A direct mantle exposure
has commonly been suggested in this regard. Our detailed observations of the morphological and spectral
diversity in the olivine-bearing exposures at Copernicus have provided critical constraints on their origin
and source regions, emphasizing multiple formation mechanisms. These findings directly impact the
interpretation of olivine exposures elsewhere on the Moon. Olivine can occur in diverse environments
including an impact melt origin, and therefore it is unlikely for all olivine exposures to be direct mantle
occurrences as has generally been suggested.
© 2015 Elsevier B.V. All rights reserved.
1. Introduction
Olivine is commonly the first crystallizing solid during magmatic differentiation and resides largely in the mantle of differentiated planetary bodies such as the Earth and the Moon (e.g. Snyder
et al., 1992). Near-surface occurrences of olivine dominated lithologies are therefore unusual unless produced through secondary processes like volcanism or plutonism. In the case of the Moon, mantle overturn has been suggested to have brought early cumulates
(including olivine) to shallower depths and subsequently led to the
formation of Mg-suite rocks (including olivine-bearing lithologies
such as troctolites) by interaction with crustal rocks (e.g. Hess,
1994; Elkins-Tanton et al., 2002; Elardo et al., 2011). Knowledge
gaps still exist for both the mantle overturn and formation of Mgsuites rocks but their existence on the lunar surface (and in our
sample collection) suggests some mechanism for their relatively
shallow origin. In addition to internal evolutionary processes, im-
*
Corresponding author. Tel.: +1 401 451 8785. Present address: Dept. of Physics,
University of Idaho, 875 Perimeter Drive MS 0903, Moscow, ID 83844, USA.
E-mail address: [email protected] (D. Dhingra).
http://dx.doi.org/10.1016/j.epsl.2015.03.039
0012-821X/© 2015 Elsevier B.V. All rights reserved.
pact craters can excavate and relocate subsurface minerals from
various depths leading to their exposure at the surface, with larger
craters excavating relatively deeper than smaller craters. Central
peaks of impact craters represent some of the deepest material
sampled within a crater. Their steep slopes minimize soil retention and aid in the identification of constituent mineralogy, revealing compositions from depth (e.g. Tompkins and Pieters, 1999;
Cahill et al., 2009).
Olivine on the lunar surface was first discovered remotely in
the central peaks of Copernicus crater (Pieters, 1982) and interpreted to be sourced from the mantle or a buried pluton (e.g.
Pieters and Wilhelms, 1985). Later studies suggested a relatively
shallow source region (e.g. Lucey et al., 1991) based on potential
olivine-bearing locations in the northern crater wall and the assumption that olivine in the wall and the peak had a common
origin. Several additional olivine-bearing exposures have been detected using recent datasets (e.g. Pieters et al., 2011; Kramer et
al., 2013). A variety of geological scenarios have been proposed to
invoke a mantle origin for olivine exposures on the Moon, including excavation through a thin crust (e.g. Yamamoto et al., 2010),
multiple impacts in a given region (allowing access to deeper material) (e.g. Pieters and Wilhelms, 1985), and a single giant impact
96
D. Dhingra et al. / Earth and Planetary Science Letters 420 (2015) 95–101
event (e.g. Yamamoto et al., 2010). Diverse origins of olivine continue to be proposed (e.g. Powell et al., 2012; Corley et al., 2014;
Sun and Li, 2014). Here, we analyze the olivine-bearing exposures
at Copernicus crater (previously known occurrences as well as
some new ones) and highlight their different geological settings
and origins. The critical implications of these findings for olivine
occurrences elsewhere on the Moon are also discussed.
2. Data and methods
In this study, we have integrated a variety of remote sensing data, from multiple lunar missions. The spectral and spatial data used here are archived and available in public domain.
Chandrayaan-1 M3 (e.g. Pieters et al., 2009; Goswami and Annadurai, 2009), LRO NAC (e.g. Chin et al., 2007; Robinson et al.,
2010) and Lunar Orbiter Laser Altimeter (LOLA) (e.g. Smith et al.,
2010) datasets are available on the Planetary Data System (PDS)
(http://pds.nasa.gov) while Kaguya TC data (e.g. Haruyama et al.,
2008) are available on the SELENE Data Archive (http://l2db.selene.
darts.isas.jaxa.jp/).
M3 data were acquired in various phases known as optical periods and which represent various imaging conditions (Boardman
et al., 2011). In this study, we used data from optical periods
Op2c1 and Op2a. Mosaics were created for each optical period using imaging strips covering the area of study. The choice of the
optical period was guided by the areal coverage, illumination conditions and spatial resolution. In this context, Op2c1 data was used
because of its better viewing geometry which minimized shadows
and facilitated detection of albedo differences. Op2a data was helpful due to its better data quality which could be used to identify
small scale compositional differences. We used the Level 2 data for
both optical periods which is publicly available and has all major
corrections (viz. photometric, thermal) applied to it (e.g. Green et
al., 2011).
The reflectance data from M3 was initially used to derive various spectral parameters that allow general mapping of compositional differences in a spatial context. The M3 parameters used in
this study are described in supplementary information (Table 1).
Subsequently, representative spectra from the study region were
extracted to highlight the observed character of olivine lithologies.
The spectra are presented as general reflectance variations and in
a continuum-removed form, the latter highlighting fine-scale compositional differences. A linear continuum was estimated (for each
spectrum) based on the spectral slope between 750 nm–1618 nm.
The spectrum was then divided by the estimated continuum to
evaluate diagnostic features.
3. New observations and insights
We have carried out detailed spectral and morphological analyses at Copernicus crater (9.62◦ , 339.92◦ ; 96 km) on the lunar near
side. It is a young, well-developed complex crater with a raised
rim, well-formed terraces, extensive melt-covered floor and central peaks. Prominent occurrence of olivine throughout the central
peaks and a well-defined olivine-bearing exposure in the northern wall (both outlined in red in Fig. 1b) are readily recognized
in M3 spectra. We report several new observations about these
known olivine occurrences and discuss additional olivine-bearing
exposures identified in this study.
3.1. Major albedo differences in olivine-bearing lithologies
Photometrically-corrected high sun (low-phase angle) observations minimize shadows and maximize the ability to identify mineralogical and brightness differences. In this context, we note that
Fig. 1. Observed albedo differences between olivine-bearing central peaks and the
northern wall exposure. (a) M3 Op2c1 image highlighting bright central peaks and
the relatively dark olivine-bearing northern wall. (b) The same image with the two
locations outlined in red. Image Id: M3G20090610T030313. The phase angle for the
acquired data was about 13◦ . Scale bar, 48 km. (c) M3 Op2c1 reflectance values
measured at 750 nm for the olivine bearing central peaks (light green bars), northern wall (dark green bars) and nearby locations (brown bars). (d) M3 Op2a spectra
illustrating the differences between olivine exposures in the low-albedo northern
wall and the central peaks.
the northern wall olivine-bearing exposure exhibits a dramatically lower albedo compared to the olivine-bearing lithology in the
peaks. A comparison of albedo around 750 nm for various locations
D. Dhingra et al. / Earth and Planetary Science Letters 420 (2015) 95–101
97
Fig. 2. Geologic context of the low-albedo olivine-bearing northern wall unit. (a) Kaguya image of the northern wall containing the low-albedo olivine-bearing unit (yellow
box). Scale bar is 4 km. (b) M3 color composite overlain on the Kaguya image illustrating the correspondence of strong olivine signature in the wall (red color in yellow
box) with the low-albedo deposit. Red = strength of 1000 nm absorption band, green = strength of 2000 nm absorption, blue = reflectance at 1489 nm. (c) LRO NAC image
(M1101338216RE) of the region (marked by the yellow box in (a) and (b)) showing the distinctive low-albedo unit. Magenta box denotes area shown in (d). Scale bar is
1 km. (d) Distal portion of the low-albedo unit in LRO NAC image (M127063668RE) illustrates the superposed nature of the deposit. Orange box denotes the area shown
in (e). Scale bar is 300 m. (e) LRO NAC view (M127063668RE) showing the subsurface topography poking through the deposit. A fresh crater exposes bright wall material
from beneath the deposit. Scale bar is 40 m. (f) Kaguya oblique image (SP_2B2_01_06758_N111_E3400P) showing the extension (green arrows) of the low-albedo wall unit
beyond the rim (also partially captured in (b)). Scale bar is 800 m. White arrow in (a), (b) and (f) marks the location of an impact melt pond.
is shown in Fig. 1c. The reported values were calculated by averaging reflectances around 750 nm (730–770 nm) and over several
pixels for each of the selected areas (see supplementary Fig. S1).
Contiguous M3 spectra (Fig. 1d) illustrate the brightness differences very well with the northern wall olivine-bearing exposure
having a consistently low-albedo across the visible to near-infrared
wavelength range. In fact, the northern wall unit exhibits the lowest albedo in the entire region when compared to the material
near the peaks and the neighboring wall, highlighting its distinctive nature. Additional measurements of albedo differences are
presented in Supplementary Fig. S2. It should be noted that although albedo variations could be strongly influenced by local topography, those effects do not significantly affect our observations
here due to multiple reasons. There is already a photometric correction applied for the local topography based on LRO LOLA observations (Smith et al., 2010). The spatial scale of observations, both
at the northern wall and the peaks, is relatively large (>1 km) and
spans local slopes providing confidence that the observed brightness differences are real. Lastly, the magnitude of difference in
albedo (40%) strengthens the argument even further when considered together with the previous constraints.
3.2. Distinct morphology of the northern wall olivine-bearing unit
A second major observation documents the distinctive geologic
context of the olivine-bearing, low-albedo northern wall unit and
is illustrated in Fig. 2 with high spatial resolution data from LRO
NAC (∼1 m/pixel) and Kaguya TC (10 m/pixel). The low-albedo
unit occurs as a relatively continuous, linear feature about 3.5 km
long and 0.5–1 km wide, extending down slope from a prominent
crater wall terrace that contains an impact melt pond (Fig. 2a,
b, f, melt pond marked with white arrow). The morphology of
the lower section is quite distinct. At the very distal end, there
is a sharp boundary between the low-albedo unit and the bright
(boulder-rich) northern wall material. The low-albedo unit occurs
as a dark apron with undulating boundaries spread across the wall,
likely guided by the local topography (illustrated in Fig. 2d; also
see supplementary Fig. S3 for slopes in the area). It mantles the
wall as a thin-deposit with sub-surface topography visible through
it. Occasionally, bright boulder material from the wall can be observed protruding through the low-albedo unit or excavated by
small craters (shown in Fig. 2e). All these properties indicate that
the low-albedo feature is likely to be an impact melt deposit.
A likely continuation of the low-albedo unit appears to extend
beyond the crater rim and is best seen in Fig. 2f. This rim unit
also displays a broad (but weaker) absorption band near 1000 nm
(black spectrum in Fig. 3c and d). There are a few other lowalbedo streaks in the vicinity and in other parts of the crater (e.g.
eastern and southern rim) but many of them have a spectrally different character including detectable contributions from pyroxene
and possibly quenched glass, apart from olivine. Additional details
on these diverse features are provided in supplementary Fig. S4.
3.3. Olivine-bearing exposures on the crater floor away from the central
peaks
A third new observation is the identification of several small,
isolated olivine-bearing exposures on the impact melt-rich crater
floor (Fig. 3a with red and blue filled circles). These locations
display distinctive spectral properties that are similar to the confirmed olivine-bearing exposures discussed above (see Fig. 3c for
comparison). This represents a third geological setting (in addition
to the central peaks and northern wall) for olivine-bearing lithologies at Copernicus crater.
The olivine-bearing floor exposures (represented by both red
and blue circles/spectra) are generally clustered in the north-west
part of the crater floor (Fig. 3a) and are associated with small,
high standing mounds (Fig. 3b), or fresh craters in the melt sheet.
An evaluation of the geologic context for each occurrence and the
nature of their spectra has been made and compared with the
other olivine-bearing lithologies. Spectra of olivine exposures on
the floor have higher albedo than the northern wall olivine spec-
98
D. Dhingra et al. / Earth and Planetary Science Letters 420 (2015) 95–101
Fig. 3. Nature and distribution of the olivine exposures at Copernicus crater. (a) The locations of olivine/quenched glass-bearing floor exposures marked as filled circles. Red
outlines show olivine-bearing central peaks and the northern wall exposure. Scale bar is 45 km. Spectra of the numbered floor locations are presented in (c) and (d) and
colored the same way. (b) Kaguya TC image showing geologic context of two crater floor locations (7, 10) displaying strong 1050 nm absorption, M3 color composite overlays
are shown with same parameters as in Fig. 2b. (c) Spectra of numbered crater floor exposures. The spectra from the central peaks, northern wall and rim above the wall
exposure are provided for comparison. (d) Same spectra as (c) but with continuum removed. Vertical dotted line at 1050 nm in (c) and (d) marks the central absorption in
olivine. Scale bars, 700 m.
trum (Fig. 3c and d) making them spectrally more comparable to
the central peaks. The areas identified with filled red circles in
Fig. 3a display absorption bands centered around 1050 nm with
no feature at 2000 nm and have comparable band strength (e.g.
spectrum 9, 10 in Fig. 3d) to the known olivine occurrences. We
interpret these as olivine-bearing. Several other areas on the crater
floor (blue filled circles in Fig. 3a) also display a broad absorption band around 1000 nm confirming their slightly mafic character. These spectra are however, noisier and have variable band
strength, making it difficult to confirm a composite nature of the
1000 nm absorption, which would be diagnostic of olivine. Despite
the broad spectral similarity with known olivine-bearing occurrences, this group may also be interpreted as fully melted and
quickly quenched glass (Bell et al., 1976; Horgan et al., 2014)
which has a broad absorption around 1000 nm. However, a weak
absorption short of 2000 nm, usually present in quenched glass,
is not seen in our data. Since quenched glass might be present in
impact melt deposits, we do not rule out its presence in some of
these locations.
Nevertheless, the occurrence of olivine-bearing lithologies on
the crater floor is clearly indicated by the spectral character of
the first group (red colored circles). The additional exposures (blue
colored circles), if confirmed to be olivine-bearing instead of glassrich, would further expand the spatial extent of olivine-bearing
lithologies on the floor. However, if found to be glass-rich, these
additional exposures would represent a section of the impact melt
that cooled relatively rapidly. The spatial distribution of small, lo-
calized olivine-bearing exposures could indicate whether olivinebearing lithology was geographically extensive in the pre-impact
target material or rather limited. Detailed compositional mapping
across the crater (Dhingra, 2015) suggests that there are also a
few small, isolated olivine-bearing exposures scattered in different
parts of the crater, an indication of perhaps a more widespread
distribution of olivine at Copernicus than previously recognized.
4. Discussion
Olivine-bearing lithologies have now been documented in association with the three genetically different crater units at Copernicus (central peaks, wall deposits and the impact melt-rich floor),
each sampling a different depth (e.g. Cintala and Grieve, 1998)
and/or having undergone different geological processing. An affiliation with impact melt is noted in two cases (northern wall
and floor). Since recent geophysical results from Gravity Recovery
and Interior Laboratory (GRAIL) mission (e.g. Zuber et al., 2013;
Wieczorek et al., 2013) do not indicate the presence of a significantly thin crust at Copernicus, direct mantle access was unlikely
during the cratering event.
The source of observed olivine at Copernicus thus appears to
have originally been located within the crustal column and may
have occurred within previously deposited basin ejecta (e.g. Imbrium or Insularum) or a buried shallow pluton (e.g. Pieters and
Wilhelms, 1985; Andrews-Hanna et al., 2013). Alternatively, olivine
could have originated in an impact melt by secondary processing
D. Dhingra et al. / Earth and Planetary Science Letters 420 (2015) 95–101
of a heterogeneous crustal column. Mare basalt is known to be
part of the pre-impact target geology at Copernicus (e.g. Schmitt
et al., 1967) and could have contributed a mafic component to the
impact melt which later crystallized olivine as it cooled. In order
to determine how the distinctly different olivine exposures recognized at Copernicus may have originated, each occurrence needs
to be evaluated separately in its specific geologic context.
4.1. Origin of olivine in the central peaks and crater floor
In the case of olivine-bearing central peaks, their formation is
believed to have involved transportation of material from ∼15 km
depth (e.g. Cintala and Grieve, 1998) in a relatively coherent, although likely highly shocked form (e.g. Melosh, 1982). The relatively bright peak material has been interpreted to be a mixture of
plagioclase and olivine in different proportions (e.g. Pieters, 1982).
The olivine-bearing exposures on the crater floor (mostly high
standing mounds) likely represent broken, un-melted large fragments that became embedded in the impact melt, perhaps from
the same source lithology as the central peaks (e.g. Dhingra, 2015).
In addition, exposures associated with small craters could either
be part of the melt sheet or could still be broken pieces from the
peaks but much smaller in size compared to the large mounds.
Some of the floor exposures could also be interpreted in terms
of intimate mixtures of olivine and quenched glass that crystallized out of impact melt. The spectral character of these occurrences have a broad absorption band around 1000 nm instead of a
well-defined set of three absorption bands characteristic of olivine.
However, it is beyond the capabilities of the current dataset to unambiguously resolve these two possibilities.
4.2. Origin of olivine on the northern wall
The northern wall olivine exposure has no observable large
boulders (in contrast to the olivine-bearing high standing mounds
on the crater floor) and instead appears quite smooth. The notable
low-albedo requires a pervasive opaque component, an important
distinguishing property in comparison to other olivine-bearing occurrences at Copernicus. The strong, composite absorption band
around 1050 nm (northern wall, Fig. 3d) suggests that the crystalline olivine is relatively abundant or has a notably coarse grain
size within a darker matrix. These combined characteristics indicate that the olivine-bearing northern wall exposure is compositionally distinct from the olivine in the central peaks and on the
crater floor. This finding marks an important departure from the
previous interpretations (e.g. Lucey et al., 1991) where the potential olivine-bearing nature of the wall deposit was equated with
the olivine-bearing character of the central peaks and a shallow
source for both occurrences was thus hypothesized.
There is currently no unique interpretation for the origin of the
low-albedo olivine-bearing wall unit, although a mafic-rich component tapped by the impact and incorporated into the impact
melt appears essential. We propose that part of this mafic component was retained as a relatively opaque glass which led to
the significant lowering of the albedo of the deposit. One scenario
could involve a cooling history in which large olivine crystals initially formed in a mafic melt but a sudden disturbance led to the
rapid cooling of the remaining melt fraction giving rise to a dark
(opaque), glassy melt matrix (with embedded large olivine crystals). Structural re-adjustments during the modification stage of
the cratering process, could potentially represent such a disturbance. Such an event could also lead to the breaching of a crystallizing melt pond and cause it to flow down the crater wall. The
resulting morphology would be consistent with the linear nature
of the observed deposit on the northern wall. Our observations
about a part of the linear deposit continuing beyond the crater
99
wall, onto the crater rim suggests that the two entities (wall exposure and rim segment) are vertically offset and provides some
credibility to the interpretation of a crater re-adjustment event.
Another scenario for the formation of olivine could be a
quenched environment involving olivine crystals in an opaquerich, fine-grained glassy matrix. Here, the olivine grains could exist
in the form of un-melted, small clasts, derived from an olivinebearing unit in the original target material (e.g. McCormick et
al., 1989). However, in the current context, it may or may not be
linked to the source of olivine-bearing units in the central peaks.
Alternatively, devitrification of mafic glassy matrix could give rise
to olivine needles (e.g. Weitz et al., 1999). In either of the cases
suggested above (olivine originating as a clast or a devitrified product), olivine crystals are required to give an optical signature while
the surrounding material is still largely opaque and/or strongly
absorbing. It has been suggested that the abundance of mafic minerals such as olivine occurring in the presence of ferrous glass
should be more than 20% in order to be detectable (e.g. Horgan et
al., 2014). This may provide a lower estimate of olivine abundance
under this scenario although it would also depend on the relative
grain sizes of the glass and olivine grains.
A third scenario could involve excavation of a pre-existing
olivine-rich pyroclastic deposit that also contains partially quenched, opaque mafic glass. Large pyroclastic deposits (e.g. Sinus Aestuum, Rima Bode) in the close vicinity to Copernicus crater are
consistent with such a geological environment. At the same time,
we note that there are no currently known remotely detectable
olivine-bearing pyroclastic deposits and therefore if this scenario
is true, the northern wall olivine exposure would be a rare variety
of pyroclastic deposit.
Lastly, an exogenic origin of some of the olivine occurrences
has been hypothesized since olivine is known to be present in
some of the asteroid classes (e.g. 246 Asporina) and its retention
as fragments has been thought to be possible under certain impact
conditions (e.g. Yue et al., 2013). However, we do not find any geologic evidence at Copernicus that support such an exogenic origin
for the observed exposures.
Among the various possibilities suggested above for the origin
of northern wall olivine-bearing exposure, we prefer the simple
case in which olivine-bearing clasts from the original target material were entrained into a mafic impact melt which cooled rapidly.
As a consequence, the final product was a mixture of opaque mafic
glass and crystalline olivine grains.
5. Potential implications for olivine occurrences on the Moon
The observed morphological diversity and brightness differences amongst olivine-bearing exposures at Copernicus crater
highlight the fact that even within a single impact crater, similar mineralogy may not always indicate the same origin and it is
very important to know the relevant geological context before genetic linkages are established.
Our findings at Copernicus crater have critical implications for
the mineralogical interpretations across the lunar surface (both
global and regional) in terms of source region and crustal mineralogical diversity. The reported observations have relevance for
all mineral species and are not necessarily restricted to olivine occurrences alone. In the case of olivine mineralogy, its occurrence
around basins (along with other information) has been used as an
indicator of a possible mantle origin (e.g. Yamamoto et al., 2010).
However, as shown in this study, olivine-bearing lithologies need
not always be derived as a primary lithology from a unique horizon at depth. It is possible that a given olivine exposure has a
secondary origin in terms of recrystallization from an impact melt
or even a tertiary origin in terms of recycling of the primary and
secondary sources, perhaps in the form of an un-melted clast em-
100
D. Dhingra et al. / Earth and Planetary Science Letters 420 (2015) 95–101
bedded in a pool of impact melt. Therefore, it is imperative to
compare all the exposures of a given mineralogy at the highest
possible spatial resolution, before their collective occurrence is interpreted.
6. Summary
The integrated analysis presented here documents different
spectral and morphological characteristics of olivine-bearing occurrences within Copernicus crater. The distinctive albedo differences
between olivine-bearing exposures in the northern wall and the
central peaks indicate that different geological processes (and possible source regions) were involved in their formation. We propose that olivine-bearing lithologies in the northern wall exposure and the crater floor are associated with impact melt and
therefore these rocks have a secondary or tertiary origin. The association with impact melt also suggests that the bulk of these
olivine-bearing materials were likely to have been derived from
a relatively shallow source depth. In contrast, the olivine-bearing
central peaks have a primary origin and represent an olivine lithology occurring at depth, below the melted zone, which was uplifted
and brought to the surface during the impact process. The olivinebearing lithologies at Copernicus are therefore diverse and did not
all form in the same way.
The presence of olivine is detected on the basis of its diagnostic
spectral signature in remote sensing data but the spectral detection does not constrain its petrographic/petrologic form. Olivine
may occur in a variety of forms such as an un-melted primary
mineral clast, recrystallized melt or devitrified glass. This study
demonstrates that apart from spectral identification, it is also very
important to analyze the geologic context of olivine-bearing locations at high spatial resolution and to identify morphological
distinctions that may be related to the nature and genetic linkages of olivine. These findings are of critical relevance to olivine
occurrences elsewhere on the Moon, including large basins (e.g.
Yamamoto et al., 2010) and are also applicable to other mineral
species. Taken collectively, there are direct implications for the
mineralogical diversity of the lunar crust. In interpreting any occurrence of mineral, the following question must be asked: Is all
the observed diversity primary in nature or is there a significant
secondary component (associated with impact melt)?
The distinct differences in the geologic context of olivine at
Copernicus, document a genetic diversity for olivine that is likely
common across the lunar crust. In this context, Copernicus remains
a scientifically high priority target for future missions.
Acknowledgements
This research was supported by SSERVI Grant No. NNA14AB01A.
We wish to thank Dr. Briony Horgan and an anonymous reviewer for their careful reading and valuable suggestions that have
helped in improving the manuscript. We also wish to thank ISRO
Chandrayaan-1 team for flying the M3 instrument and Kaguya and
LROC teams for making available an excellent set of image data
that nicely complements spectral observations.
Appendix A. Supplementary material
Supplementary material related to this article can be found online at http://dx.doi.org/10.1016/j.epsl.2015.03.039.
References
Andrews-Hanna, J.C., et al., 2013. Ancient igneous intrusions and early expansion
of the Moon revealed by GRAIL Gravity Gradiometry. Science 339, 675–678.
http://dx.doi.org/10.1126/science.1231753.
Bell, P.M., Mao, H.K., Weeks, R.A., 1976. Optical spectra and electron paramagnetic
resonance of lunar and synthetic glasses: a study of the effects of controlled
atmosphere, composition, and temperature. In: Proceedings 7th Lunar Science
Conference, pp. 2543–2559.
Boardman, J.W., et al., 2011. Measuring moonlight: an overview of the spatial properties, lunar coverage, selenolocation, and related level 1B products of the Moon
Mineralogy Mapper. J. Geophys. Res. 116, E00G14. http://dx.doi.org/10.1029/
2010JE003730.
Cahill, J.T.S., Lucey, P.G., Wieczorek, M.A., 2009. Compositional variations of the lunar
crust: results from radiative transfer modeling of central peak spectra. J. Geophys. Res. 114, E09001. http://dx.doi.org/10.1029/2008JE003282.
Chin, G., et al., 2007. Lunar reconnaissance orbiter overview: the instrument suite
and mission. Space Sci. Rev. 129, 391–419.
Cintala, M.J., Grieve, R.A.F., 1998. Scaling impact melting and crater dimensions:
implications for the lunar cratering record. Meteorit. Planet. Sci. 33, 889–912.
http://dx.doi.org/10.1111/j.1945-5100.1998.tb01695.x.
Corley, L.M., McGovern, P.J., Kramer, G.Y., 2014. Olivine exposures on the Moon:
origins and mechanisms of transport to the lunar surface. In: 45th Lunar and
Planet. Sci. Conf. Abstract #1564.
Dhingra, D., 2015. Integrated mineralogy and high resolution geologic context of
lunar impact melt deposits: implications for crustal diversity and the impact
cratering process. PhD thesis. Brown University. 523 pp.
Elardo, S.M., Draper, D.S., Shearer, C.K.J., 2011. Lunar Magma Ocean crystallization
revisited: bulk composition, early cumulate mineralogy, and the source regions of the highlands Mg-suite. Geochim. Cosmochim. Acta 75 (1), 3024–3045.
http://dx.doi.org/10.1016/j.gca.2011.02.033.
Elkins-Tanton, L.T., Van Orman, J.A., Hager, B.H., Grove, T.L., 2002. Re-examination
of the lunar magma ocean cumulate overturn hypothesis: melting or mixing
is required. Earth Planet. Sci. Lett. 196 (3), 239–249. http://dx.doi.org/10.1016/
S0012-821X(01)00613-6.
Goswami, J.N., Annadurai, M., 2009. Chandrayaan-1: India’s first planetary science
mission to the Moon. Curr. Sci. 6 (4), 486–491.
Green, R.O., et al., 2011. The Moon Mineralogy Mapper (M3 ) imaging spectrometer
for lunar science: instrument description, calibration, on-orbit measurements,
science data calibration and on-orbit validation. J. Geophys. Res. 116, E00G19.
http://dx.doi.org/10.1029/2011JE003797.
Haruyama, J., et al., 2008. Global lunar-surface mapping experiment using the lunar
imager/spectrometer on SELENE. Earth Planets Space 60, 243–256.
Hess, P.C., 1994. Petrogenesis of lunar troctolites. J. Geophys. Res. 99 (E9),
19083–19093. http://dx.doi.org/10.1029/94JE01868.
Horgan, B., Cloutis, E., Mann, P., Bell, J., 2014. Near-infrared spectra of ferrous mineral mixtures and methods for their identification in planetary surface spectra.
Icarus 234, 132–154. http://dx.doi.org/10.1016/j.icarus.2014.02.03.
Kramer, G.Y., Kring, D.A., Nahm, A.L., Pieters, C.M., 2013. Spectral and photogeologic
mapping of Schrödinger basin and implications for post-South Pole-Aitken impact deep subsurface stratigraphy. Icarus 223, 131–148.
Lucey, P.G., Hawke, B.R., Horton, K., 1991. The distribution of olivine in the crater
Copernicus. Geophys. Res. Lett. 18 (11), 2133–2136.
McCormick, K.A., Taylor, G.J., Keil, K., Spudis, P.D., Grieve, R.A.F., 1989. Sources of
clasts in terrestrial impact melts – clues to the origin of LKFM. In: Proc. 19th
Lunar Planet. Sci. Conf., pp. 691–696.
Melosh, H.J., 1982. A schematic model of crater modification by gravity. J. Geophys.
Res. 87 (B1), 371–380.
Pieters, C.M., 1982. Copernicus crater central peak: lunar mountain of unique composition. Science 215, 59–61.
Pieters, C.M., Wilhelms, D.E., 1985. Origin of olivine at Copernicus. In: Proc. 15th
Lunar Planet. Sci. Conf., Part 2. J. Geophys. Res., C415–C420.
Pieters, C.M., et al., 2009. The moon mineralogy mapper (M3 ) on Chandrayaan-1.
Curr. Sci. 96, 500–505.
Pieters, C.M., et al., 2011. Mg-spinel lithology: a new rock type on the lunar farside.
J. Geophys. Res. 116, E00G08. http://dx.doi.org/10.1029/2010JE003727.
Powell, K.E., McGovern, P.J., Kramer, G.Y., 2012. Olivine detections on the rim of
Crisium basin with Moon Mineralogy Mapper. In: 43rd Lunar and Planet. Sci.
Conf. Abstract #1689.
Robinson, M.S., et al., 2010. Lunar reconnaissance orbiter camera (LROC): instrument
overview. Space Sci. Rev. 150, 81–124.
Schmitt, H.H., et al., 1967. Geologic map of the Copernicus quadrangle of the Moon.
USGS Map I-515 (LAC-58).
Smith, D.E., et al., 2010. The lunar orbiter laser altimeter investigation on the lunar
reconnaissance orbiter mission. Space Sci. Rev. 150 (1–4), 209–241.
Snyder, G.A., Taylor, L.A., Neal, C.R., 1992. A chemical model for generating the
sources of mare basalts: combined equilibrium and fractional crystallization of
the lunar magmasphere. Geochim. Cosmochim. Acta 56, 3809–3823.
Sun, Y., Li, L., 2014. Global investigation of olivine bearing crater central peaks with
M3 images. In: 45th LPSC. Abstract #1653.
Tompkins, S., Pieters, C.M., 1999. Mineralogy of the lunar crust: results from clementine. Meteorit. Planet. Sci. 34, 25–41.
Weitz, C.M., Rutherford, M.J., Head III, J.W., McKay, D.S., 1999. Ascent and eruption
D. Dhingra et al. / Earth and Planetary Science Letters 420 (2015) 95–101
of a lunar high-titanium magma as inferred from the petrology of the 74001/2
drill core. Meteorit. Planet. Sci. 34, 527–540.
Wieczorek, M.A., et al., 2013. The crust of the Moon as seen by GRAIL. Science 339,
671–675. http://dx.doi.org/10.1126/science.1231530.
Yamamoto, S., et al., 2010. Possible mantle origin of olivine around lunar impact
basins detected by SELENE. Nat. Geosci.. http://dx.doi.org/10.1038/NGEO897.
101
Yue, Z., Johnson, B.C., Minton, D.A., Melosh, H.J., Di, K., Hu, W., Liu, Y., 2013. Projectile remnants in central peaks of lunar impact craters. Nat. Geosci. 6 (6),
435–437. http://dx.doi.org/10.1038/ngeo1828.
Zuber, M.T., et al., 2013. Gravity field of the Moon from the gravity recovery and
interior laboratory (GRAIL) mission. Science 339, 668–671. http://dx.doi.org/
10.1126/science.1231507.