In un paese come l`Italia, caratterizzato da una forte densità abitativa

Scuola di Dottorato in Scienze della Terra,
Dipartimento di Geoscienze, Università degli Studi di Padova – A.A. 2010-2011
THE HERMEAN SURFACE: THE INTERPLAY BETWEEN REMOTE SENSING IMAGING
AND SPECTRAL SIGNATURE
Ph.D. candidate: FERRARI SABRINA,
Tutors: Dott. MATTEO MASSIRONI, Prof. FABRIZIO NESTOLA
Cycle: XXV
Abstract
The special yield of remote sensing data from the recent Mercury Surface Space ENvironment GEochemistry and Ranging
NASA mission - MESSENGER - currently allows a detailed analysis of litotypes and structural forms of the hermean surface.
Thus, a geological classification of the domains and the features concerning impact basins - stratigraphy, composition and
ages - could be easily reached through the elaboration and interpretation of remote sensing multi-band images and
spectroscopic in-situ analysis, attempting to set up in laboratory the same environment of Mercury. The first year Ph.D. work
has been dedicated to the remote sensing study of one of the most representative hermean basin, named Rembrandt Basin. At
the same time, spectroscopic and diffraction data set have been collected on representative geological materials of the
Mercury surface at its typical temperature range.
Introduction
During its second and third flybys, MESSENGER imaged a new large and well-preserved basin called
Rembrandt Basin located at Mercury’s southern hemisphere (Watters et al., 2009). Rembrandt basin is a
715-km-diameter impact feature which displays a distinct hummocky rim, broken up by the presence of
several large impact craters. Its interior is partially filled by volcanic materials, that extend up to the
southern, eastern and part of the western rims, and is crossed by a marked lobate scarp.
In the first stage of our studies, MESSENGER Mercury Dual Imaging System (MDIS) mosaics1 have
been used to map its geological domains and infer - where possible - their stratigraphic relationships. At
the same time, the contractional and extensional local patterns and the global tectonic features have been
well-fixed. Then, crater counts have been performed on each unit, in order to estimate the ages by
applying the Model Production Function (MPF) (Marchi et al., 2009).
A further aim of MESSANGER is mapping the composition of the hermean surface by the Mercury
Atmospheric and Surface Composition Spectrometer (MASCS), that has already produced a first average
spectrum along an approximate equatorial trajectory (McClintock et al., 2008). In this light, the second
stage of the Ph.D. project wants to take into account the large day-night thermal variation occurred along
the hermean equatorial surface, which can strongly affect the surface mineral spectral features. In
particular, the spectral variations of the main minerals assumed to be present on the Mercury surface have
been investigated as a function of temperature by in situ measurements performed in laboratory. Beyond
the spectroscopic measurements, in situ X-ray diffraction data will be collected from 10 to 730 K on the
same samples measured by spectroscopy in order to define the volume thermal coefficients and to explain
any possible spectral variations in terms of structure change.
Geo-structural mapping
Rembrandt Basin displays evidence of both global-scale and basin-localized deformations possibly
controlled by the rheological layering within the crust. Extensional features are essentially radial and
confined to the Inner Plains, displaying one or more uplifts episodes of the inner basin. The more
widespread wrinkle ridges form a polygonal pattern of radial and concentric features on the whole floor,
probably due to one or more near-surface compressional stages (Watters et al., 2009). Thus, through their
cross-cutting relationships, it is attempted to distinguish the cascade of events. About global landforms, a
structural and kinematic analysis focused on the mayor 1000-km long Rembrandt scarp has been
conducted. The structure can be subdivided into three branches: the southern one with clear evidences of
a right-lateral strike slip movement acting together with an inverse kinematic, the northern one (fig. 1)
with some evidences of a left-lateral component and the central sector without a great evidence of strike
slip movements. The inferred propagation trend is South-East.
1
Scuola di Dottorato in Scienze della Terra,
Dipartimento di Geoscienze, Università degli Studi di Padova – A.A. 2010-2011
The resulting bow shape geometry could be compared with the
Beagle Rupes (Rothery and Massironi, 2010) feature despite
Rembrandt structure does not show a clear frontal ramp but
two lateral ramps converging in a narrow cusp, which is
characterized by a steep surface-breaking thrust. The main
phase responsible of the Rembrandt scarp build-up was
followed by minor compressional structures detected within
younger craters and possibly associated to a slowing down
phase of the global contraction.
Figure 1. Rembrandt Basin from MESSENGER MDIS-NAC image and (a)
geological sketch of the northern-branch of Rembrandt scarp over the geological
map: Hummocky Area (red color), Proximal Ejecta (pale grey color) , Inner Plains
(red color), surface-breaking thrust (white lines).
Age determination
The basin has been subdivided into three main systems for age determination purposes (fig. 1): the
Hummocky Area, a mixture of impact melts and breccias, the Proximal Ejecta fallen beyond the rim and
the volcanic Inner Plains, which flooded the crater floor after the impact. The age assessment was
obtained by adopting Marchi et al. (2009) chronological model, since it takes into account both (1) the
Main Belt Asteroids (MBAs) and the Near Earth Objects (NEOs) projectile populations and (2) the
uppermost layering of the target (Massironi et al., 2009). More in detail, a lunar-like crustal structure has
been adopted and fractured silicates of variable thickness have been set on top of a bulk anorthositic crust,
which in turn laying above a peridotitic mantle.
In the case of the Rembrandt basin system, the adopted
layering for MPF age determination was well constrained by
the good statistics and crater-diameter range of the data set.
The Crater Size-Frequency Distribution (CSFD) of the
Hummocky Area shows a typical kink, which likely reflects a
layer of fractured material with a thickness of about 8.5 km,
whereas the Inner Plains show a slight kink despite the wide
crater diameter range that characterizes their population (fig.
2). Considering these constraints on the crustal layering and an
MBAs population, the inferred MPF ages imply a short stage
of volcanism straight after the basin formation, between 3.77
and 3.82 Gy, whereas the concurrent structural analysis shows
a prolonged activity of global contraction well-expressed
along the Rembrandt scarp
Figure 2. Crater Size-Frequency Distribution
(CSFD) of the Hummocky Area (on the left) and of
the Inner Plains (on the right).
1. Greyscale images at 500 meters/pixel (~85.17 pixels/degree) resolution have been used in two different projection, depending on the aim of work. All
images are courtesy of USGS Astrogeology Science Center http://astrogeology.usgs.gov and come from MESSENGER MDIS/Mariner 10 mosaics.
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Scuola di Dottorato in Scienze della Terra,
Dipartimento di Geoscienze, Università degli Studi di Padova – A.A. 2010-2011
(Sampling to lab and) Low-high temperature behaviour
It is well known that the surface of Mercury can undergo a temperature excursion extremely large at
specific locations (Strom, 1987). The temperature can range in 44 earth days between 70 and 725 K at
different latitudes and it is easy to assume that such changes can cause strong crystal structure changes.
As a consequence, the spectral signature of minerals assumed to be present on the Mercury surface could
be significantly affected as well as the reflectance values. Aim of this work is to determine which is the
expansion of such minerals within a so wide T range in order to verify its effect on the reflectance.
As a first experiment the low-high temperature behavior of an Fe-poorer olivine has been investigated
as a possible constituent of the Mercury surface regolith. A sample with Fo92Fa8 composition - coming
from Mt. Leura (Secco and Princivalle, 1985) - has been selected and analyzed by X-ray diffraction under
non-ambient conditions, from 10 to 775 K, at the Institut für Kristallographie RWTH in Aachen,
Germany (fig. 3). Data collected in a previous work on Fo92Fa8, Fo80Fa20, Fo71Fa29 and Fo62Fa38 were
studied by single crystal X-ray diffraction, at room conditions and by using the same experimental
procedure (Nestola et al., 2010). Comparing our results with those of Nestola et al. (2010) it appears clear
that the same volume increase observed for our Fo92Fa8 sample with increasing the temperature by 635 K
is found for a 30% of increase of Fe content along the Fo-Fa binary join due to the increase of the cationic
radius for the Mg/Fe substitution. Therefore, these results indicate that the hermean surface has a
chameleon-like behavior for spectral data and that important misinterpretations can occur if the typical
temperature variations are not taken into account.
The emissivity spectra obtained under non ambient
temperature conditions at the Planetary Emissivity Laboratory
(PEL) in Berlin (Helbert et al., 2009) will clarify the effect of
iron on the volume thermal expansion of olivine. These data
will be combined with the X-ray diffraction data in order to
explain any anomaly or complexity showed by the spectra
collected under non ambient temperature conditions. To this
end, other samples of the maximum likelihood constituents of
the hermean surface regolith (Warell et al., 2010) will be
investigated: a labradorite plagioclase (extracted by a
Flakstadøy Basic Complex anorthosite, sampled in July 2010
Figure 3. Thermal expansion of the Fo92Fa8
at Lofoten Island, Norway) and two distinct Mg-rich
olivine, occurred between 10 and 775 K.
clinopyroxenes (samples 49-5858 coming from Ontario,
Canada and samples 49E-0814 coming from Oregon, USA)
have been well characterized at room conditions by single crystal X-ray diffraction and analyzed by
electron microprobe (WDS method). After then, the samples have been reduced in two different
presumed grain-sizes about the hermean surface regolith: 30 m and 100 m (Emery et al., 1998). The
emissivity measurements will be carried out at four different steps of temperature (150°-250°-350°470°C) for each grain-size. The expected results will represent first reference data with the aim to build a
complete in situ high-temperature spectral data base, capable to take into account the temperature
variations for Mercury and several planetary bodies.
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Scuola di Dottorato in Scienze della Terra,
Dipartimento di Geoscienze, Università degli Studi di Padova – A.A. 2010-2011
References
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136 (1), 104-123.
HELBERT, J. and MATURILLI, A. 2009. The emissivity of a fine-grained labradorite sample at typical
Mercury dayside temperatures. Earth and Planetary Science Letters, 285 (3-4), 347-354.
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new Chronology for the Moon and Mercury. Astronomical Journal, 137, 4936-4948.
MASSIRONI, M., CREMONESE, G., MARCHI, S., MARTELLATO, E., MOTTOLA, S. and
WAGNER, R.J. 2009. Mercury's geochronology revised by applying Model Production Function to
Mariner 10 data: Geological implications. Geophys. Res. Lett., 36, L21204.
McCLINTOCK, W.E., IZEMBERG, N.R., HOLSCLAW G.M., BLEWETT, D.T., DOMINGUE, D.L.,
HEAD, J.W., HELBERT, J., McCOY, T.J., MURCHIE, S.L., ROBINSON, M.S., SOLOMON, S.C.,
SPRAGUE, A.L. and VILAS, F. 2008. Spectroscopic Observations of Mercury's Surface Reflectance
During MESSENGER's First Mercury Flyby. Science, 321, 62-65.
NESTOLA, F., PASQUAL, D., SECCO, L., DAL NEGRO, A., NOVELLA, D., TARANTINO, S. 2010.
Elasticity of olivine. Geophysical Research Letters, submitted.
ROTHERY, D.A. AND MASSIRONI, M. 2010. Beagle Rupes – evidence for a basal decollement of
regional extent in Mercury’s lithosphere. Icarus, 209 (1), 256-261.
SECCO, L. and PRINCIVALLE, F. 1985. Crystal Structure Refinement of 13 Olivines in the ForsteriteFayalite Series from Volcanic Rocks and Ultramafic Nodules. TMPM Tschermaks Min. Petr. Mitt., 34,
105-115.
STROM, R.G. 1987. Mercury: The Elusive Planet, solar system series. Smithsonian Institution Press,
Washington, USA.
WARELL, J., SPRAGUE, A., KOZLOWSKI, R., ROTHERY, D.A., LEWIS, N., HELBERT, J. and
CLOUTIS, E. 2010. Constraints on Mercury’s surface composition from MESSENGER and groundbased spectroscopy. Icarus, 209, 138-163.
WATTERS, T.R., HEAD, J.W., SOLOMON, S.C., ROBINSON, M.S., CHAPMAN, C.R., DENEVI,
B.W., FASSETT, C.I., MURCHIE, S.L., and STROM, R.G. 2009. Evolution of the Rembrandt Impact
Basin on Mercury. Science, 324, 618-621.
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Scuola di Dottorato in Scienze della Terra,
Dipartimento di Geoscienze, Università degli Studi di Padova – A.A. 2010-2011
SUMMARY LAST YEAR’S ACTIVITY
Courses:
F. NESTOLA: “Metodologie analitiche”, Dipartimento di Geoscienze, Università degli Studi di Padova.
S. BOESSO: “Corso di introduzione alla biblioteca”, Dipartimento di Geoscienze, Università degli Studi di Padova.
A. RASSU, C. VINANTE, N. PRATICELLI: “Corso di Linux/Unix: corso introduttivo al sistema operativo Linux”,
Dipartimento di Geoscienze, Università degli Studi di Padova.
M. FLORIS: “Introduzione alle tecniche GIS”, Dipartimento di Geoscienze - Università degli Studi di Padova.
F. PESARIN, L. SALMASO: “Statistica applicata alla sperimentazione scientifica”, Dipartimento di tecnica e gestione dei
Sistemi Industriali, Università degli Studi di Padova.
V. VANZANI: “Fisica dei pianeti”, Dipartimento di Astronomia, Università degli Studi di Padova.
E. CALANDRUCCIO: “Corso di Inglese parlato”, Dipartimento di Geoscienze, Università degli Studi di Padova.
F. CAMARA: “Risoluzione strutturale di sostanze inorganiche a struttura cristallina ignota”, Dipartimento di Geoscienze,
Università degli Studi di Padova.
Schools and workshops:
CENTRO DI SERVIZI INTERDIPARTIMENTALE CUGAS, Corso teorico-applicativo sulle tecniche SEM e ESEM, II
edizione, Università degli Studi di Padova, Padova, Italy
FIRST EGU SUMMER SCHOOL, Structural Analysis of Crystalline Rocks, Nevessee Area/South Tyrol, Italy.
Communications:
MARTELLATO, E., MASSIRONI, M., CREMONESE G., MARCHI S., FERRARI S., PROCKTER L.M., 2010. Age
Determination of Raditladi and Rembrandt Basins and Related Geological Units. 41st Lunar and Planetary Science
Conference, The Woodlands/Texas, USA.
MASSIRONI M., CREMONESE G., MARCHI S., MARTELLATO E., GIACOMINI L., FERRARI S., 2010. A review of
Model Production Function age determinations on the Mercury surface. COSPAR 2010 38th sci-conference, Bremen,
Germany.
CREMONESE, G., CAPRIA, M.T., BETTANINI, C., CALAMAI, L., DEBEI, S., DA DEPPO, V., ENG, P., FERRARI, S.,
FORLANI, G., GIACOMINI, L., LANGEVIN, Y., MASSIRONI, M., MARTELLATO, E., NALETTO, G., ROCCELLA, R.,
SGAVETTI, M., SIMIONI, E., ZACCARIOTTO, M. and SIMBIO-SYS TEAMS, 2010. SIMBIO-SYS tutorial: the Stereo
Channel. MASSIRONI, M. and SIMBIO-SYS team. SIMBIO-SYS contribution to Mercury knowledge: summary of science
objectives from geologic perspective. Bepi Colombo Mission 7th Science Working Team Meeting, Graz, Austria.
Posters:
MARTELLATO E., FERRARI S., GIACOMINI L., CREMONESE G., MARCHI S., MASSIRONI M., ROTHERY D.A.,
2010. Age Determination of Raditladi and Rembrandt Basins and Related Geological Units. European Geosciences Union
assembly 2010, Wien, Austria.
FERRARI S., MASSIRONI M., MARTELLATO E., GIACOMINI L., CREMONESE G., ROTHERY D.A., PROCKTER
L.M., 2010. Geo-structural mapping and age determinations of Rembrandt Basin. COSPAR 2010 38th sci-conference,
Bremen, Germany.
NESTOLA F., FERRARI S., MASSIRONI M., CREMONESE G., VISONA’D., BRUNO M., FIORETTI A.M., CAPRIA
M.T., REDHAMMER G.J., 2010. Low-high temperature behaviour of olivine: implication for Mercury surface. 89° Congresso
Società Italiana di Mineralogia e Petrologia, Ferrara, Italy.
FERRARI S., MASSIRONI M., MARTELLATO E., GIACOMINI L., CREMONESE G., ROTHERY D.A., PROCKTER
L.M., 2010. Geo-structural mapping and age determinations of Rembrandt Basin region. European Planetary Science
Congress 2010, Roma, Italy.
Field work and lab activity:
FIELD WORK IN NORTHERN NORWAY, in collaboration with Institutt for Geologi, Universitetet i Tromsø, July 9th-17th
2010, Lofoten Islands, Norway.
SINGLE CRYSTAL X-RAY DIFFRACTION, at Dipartimento di Geoscienze, Padua, Italy.
HIGH TEMPERATURE EXPERIMENTS TO PLANETARY EMISSIVITY LABORATORY (PEL) AT DLR BERLIN,
granted by 7th Framework Programme / EuroPlanet Research Infrastructure, November 1st-12th 2010, Berlin, Germany.
Grants:
COSPAR 2010 38th sci-conference, Bremen/Germany, travel and expenses support, $850.
Submitted funding proposals:
Fondazione Ing. Aldo Gini – 2010 scholarship for Italian citizens to study abroad.
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