The Major-Element Composition of Mercury’s Surface from MESSENGER X-ray Spectrometry

Nittler, L. R.; Starr, R.; Weider, S. Z.; McCoy, Timothy J.; Boynton, W. V.; Ebel, D. S.; Ernst, C. M.; Evans, L. G.; Goldsten, J.; Hamara, D.; Lawrence, D. J.; McNutt, R. L.; Schlemm, C. E.; Solomon, Sean C.; Sprague, A. L.

doi:10.1126/science.1211567

Cited by 394 publications

(465 citation statements)

References 53 publications

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“…Ratios of S/Si are high, which points to significant amounts of sulfur at the surface of Mercury (Nittler et al, 2011). Calculated S abundances range from 1.4 to 3.7 wt% S ( Table 1).…”

Section: The Roles Of Sulfur and Iron Metalmentioning

confidence: 99%

“…The immiscible sulfide melt in these experiments is dominated by Fe (26-38 wt% Fe) and S (37-42 wt% S), and contains up to 12 wt% Ca and 12 wt% Mg. These data allow us to infer the actual silicate melt composition by taking into account the partitioning of major elements between immiscible silicate, metal and sulfide melts in the bulk composition measured by XRS (Nittler et al, 2011). We use the most conservative approach with high concentrations of lithophile elements in the sulfide and metal melts (sulfide melt with 40 wt% S, 30 wt% Fe, 15 wt% Ca and 15 wt% Mg; metal melt with 90 wt% Fe and 10 wt% Si).…”

Section: The Roles Of Sulfur and Iron Metalmentioning

confidence: 99%

“…Elemental ratios for Mg/Si, Al/Si, S/Si, Ca/Si, Ti/Si and Fe/Si have been determined because ratios are largely independent of the measurement geometry and the total composition (Schlemm et al, 2007;Nittler et al, 2011).…”

Section: Surface Compositions: Calculations and Assumptionsmentioning

confidence: 99%

“…The first measurements of surface elemental abundance ratios by MESSENGER's X-Ray Spectrometer (XRS; Nittler et al, 2011) and the Gamma-Ray Spectrometer (GRS; Peplowski et al, 2011) produced surprises based on expectations and understanding of Mercury prior to the satellite's arrival. Some volatile elements (K and S) are not depleted and the low FeO content of the surface points to highly reduced conditions (Wadhwa, 2008; Zolotov, 2011;McCubbin et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

“…In this study, XRS elemental ratios presented by Nittler et al (2011) are used to calculate absolute abundances of major elements for surface materials. Data treated in this study do not include the northern volcanic plains described by Head et al (2011).…”

Section: Introductionmentioning

confidence: 99%

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Phase equilibria of ultramafic compositions on Mercury and the origin of the compositional dichotomy

Charlier

Grove

Zuber

2013

Earth and Planetary Science Letters

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a b s t r a c tMeasurements of major element ratios obtained by the MESSENGER spacecraft using x-ray fluorescence spectra are used to calculate absolute element abundances of lavas at the surface of Mercury. We discuss calculation methods and assumptions that take into account the distribution of major elements between silicate, metal, and sulfide components and the potential occurrence of sulfide minerals under reduced conditions. These first compositional data, which represent large areas of mixed highreflectance volcanic plains and low-reflectance materials and do not include the northern volcanic plains, share common silica-and magnesium-rich characteristics. They are most similar to terrestrial volcanic rocks known as basaltic komatiites. Two compositional groups are distinguished by the presence or absence of a clinopyroxene component. Melting experiments at one atmosphere on the average compositions of each of the two groups constrain the potential mineralogy at Mercury's surface, which should be dominated by orthopyroxene (protoenstatite and orthoenstatite), plagioclase, minor olivine if any, clinopyroxene (augite), and tridymite. The two compositional groups cannot be related to each other by any fractional crystallization process, suggesting differentiated source compositions for the two components and implying multi-stage differentiation and remelting processes for Mercury. Comparison with high-pressure phase equilibria supports partial melting at pressure o10 kbar, in agreement with last equilibration of the melts close to the crust-mantle boundary with two different mantle lithologies (harzburgite and lherzolite). Magma ocean crystallization followed by adiabatic decompression of mantle layers during cumulate overturn and/or convection would have produced adequate conditions to explain surface compositions. The surface of Mercury is not an unmodified quenched crust of primordial bulk planetary composition. Ultramafic lavas from Mercury have high liquidus temperatures (1450-1350 1C) and very low viscosities, in accordance with the eruption style characterized by flooding of pre-existing impact craters by lava and absence of central volcanoes.

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“…Ratios of S/Si are high, which points to significant amounts of sulfur at the surface of Mercury (Nittler et al, 2011). Calculated S abundances range from 1.4 to 3.7 wt% S ( Table 1).…”

Section: The Roles Of Sulfur and Iron Metalmentioning

confidence: 99%

Section: The Roles Of Sulfur and Iron Metalmentioning

confidence: 99%

Section: Surface Compositions: Calculations and Assumptionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Phase equilibria of ultramafic compositions on Mercury and the origin of the compositional dichotomy

Charlier

Grove

Zuber

2013

Earth and Planetary Science Letters

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Detection and characterization of 0.5–8 MeV neutrons near Mercury: Evidence for a solar origin

et al. 2014

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[1] Data from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) Neutron Spectrometer (NS) have been used to identify energetic neutrons (0.5-8 MeV energy) associated with solar events that occurred on 4 June 2011. Multiple lines of evidence, including measurements from the NS and the MESSENGER Gamma-Ray Spectrometer, indicate that the detected neutrons have a solar origin. This evidence includes a lack of time-coincident, energetic (>45 MeV) charged particles that could otherwise create local neutrons from nearby spacecraft material and a lack of proton-induced gamma rays that should be seen if energetic protons were present. NS data cannot rule out the presence of lower-energy ions (<30 MeV) that can produce local neutrons. However, the ion spectral shape required to produce the measured neutron count rate locally is softer than any known ion spectral shape. The neutron energy spectrum shows a relative enhancement in the energy range 0.8-3 MeV compared with cosmic-ray-generated neutrons from the spacecraft or Mercury. The spectral shape of the measured neutron fluence spectrum is consistent with a previously modeled fluence spectrum of neutrons that originate at the Sun and are propagated through the MESSENGER spacecraft to the NS. These measurements provide strong evidence for a solar origin of the detected neutrons and suggest that a large number of low-energy threshold ion evaporation reactions were taking place on the Sun during the neutron event.

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The tides of Mercury and possible implications for its interior structure

et al. 2014

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Key Points:• We present models of the tidal deformation of Mercury based on MESSENGER results • Tides are sensitive to size and density of the core and rheology of outer shell • The presence of a FeS layer would increase the tidal response AbstractThe combination of the radio tracking of the MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft and Earth-based radar measurements of the planet's spin state gives three fundamental quantities for the determination of the interior structure of Mercury: mean density , moment of inertia C, and moment of inertia of the outer solid shell C m . This work focuses on the additional information that can be gained by a determination of the change in gravitational potential due to planetary tides, as parameterized by the tidal potential Love number k 2 . We investigate the tidal response for sets of interior models that are compatible with the available constraints ( , C, and C m ). We show that the tidal response correlates with the size of the liquid core and the mean density of material below the outer solid shell and that it is affected by the rheology of the outer solid shell of the planet, which depends on its temperature and mineralogy. For a mantle grain size of 1 cm, we calculate that the tidal k 2 of Mercury is in the range 0.45 to 0.52. Some of the current models for the interior structure of Mercury are compatible with the existence of a solid FeS layer at the top of the core. Such a layer, if present, would increase the tidal response of the planet.

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The Major-Element Composition of Mercury’s Surface from MESSENGER X-ray Spectrometry

Cited by 394 publications

References 53 publications

Phase equilibria of ultramafic compositions on Mercury and the origin of the compositional dichotomy

Phase equilibria of ultramafic compositions on Mercury and the origin of the compositional dichotomy

Detection and characterization of 0.5–8 MeV neutrons near Mercury: Evidence for a solar origin

The tides of Mercury and possible implications for its interior structure

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