Long‐lived explosive volcanism on Mercury

Thomas, Richard H.; Rothery, David A.; Conway, Susan J.; Anand, M.

doi:10.1002/2014gl061224

Cited by 79 publications

(63 citation statements)

References 46 publications

(71 reference statements)

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“…This peculiar distribution of the pyroclastic deposits may reflect their relatively young age [ Thomas et al , ] with respect to the effusive volcanism that fills the entire basin [ Ernst et al , ]. In fact, the subsurface structure of the Caloris basin should have many faults that penetrate deeper into the interior of Mercury at the edge of the basin [ Klimczak et al , ], thus favoring a deeper source for explosive volcanism, as often suggested for the Moon [ Gaddis et al , ].…”

Section: Mercury's Volcanismmentioning

confidence: 99%

Spectroscopic properties of explosive volcanism within the Caloris basin with MESSENGER observations

2015

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Volcanism on Mercury has been indisputably identified at various locations on the surface, by means of both effusive and explosive volcanism. Its characterization is crucial to understand the evolution of the planet, in particular the thermal evolution of the mantle, and the volatile content of the planet. This analysis presents a detailed view of the pyroclastic deposits of the Caloris basin. Observations from the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) are used to understand the spectral characteristics of the pyroclastic deposits, both in the visible and near‐infrared. Additional calibration steps are proposed to reconcile the difference of absolute reflectance between the visible (VIS) and near‐infrared (NIR) detectors. These calibration steps allow the use of the full spectral range of the MASCS instrument. Pyroclastic deposits exhibit a redder spectral slope in the VIS and NIR. This spectral slope diminishes toward the edge of the deposits to match that of Mercury's average surface. Spectral properties in the ultraviolet (UV) also change as a function of distance to the vent. Only the UV properties unambiguously separate the pyroclastic deposits from Mercury's average spectra. The spectral variations are consistent with a lower iron content of the pyroclastic deposits with respect to the average surface of Mercury, similar to what has been proposed for pyrolcastic deposits on the lunar surface. Nonetheless, given the limited illumination conditions diversity of the MASCS instrument, other causes such as grain size, space weathering, and bulk composition could also be accounted for the spectral variations. Variability of the pyroclastic deposits' properties within the entire basin are potentially identified between the three main clusters, and could be related to space weathering of deposits of different ages.

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Section: Mercury's Volcanismmentioning

confidence: 99%

Spectroscopic properties of explosive volcanism within the Caloris basin with MESSENGER observations

2015

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“…Portions of what have previously been termed intermediate plains (IPs) are also believed to be volcanically emplaced, though clear geomorphic evidence such as flow fronts has been mostly obliterated by intense cratering (e.g., Trask & Guest, 1975;Whitten et al, 2014). Geologically young pyroclastic deposits are found distributed across the globe, mostly within impact craters, though not necessarily associated with smooth plains (e.g., Goudge et al, 2014;Kerber et al, 2011;Thomas et al, 2014bThomas et al, , 2015.…”

Section: Introductionmentioning

confidence: 99%

Global Distribution and Spectral Properties of Low‐Reflectance Material on Mercury

Klima

Denevi

Ernst

et al. 2018

Geophysical Research Letters

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We examine the global distribution and spectral properties of low‐reflectance material (LRM) across Mercury to estimate the relative carbon abundance of prominent exposures and to test hypotheses for the origin of carbon in LRM. Our mapping demonstrates that LRM is consistently excavated from depth and that the spectral curvature attributed to carbon becomes more subdued as these surface deposits age. We find that the 600‐nm band depth in LRM deposits is related to carbon content and can be used to estimate carbon enrichment. LRM deposits excavated by basins and large craters may be enriched with as much as 4 wt% carbon over the local mean. Regional deposits, associated with the most heavily cratered terrains, are enriched by an average of ~2.5 wt% carbon. The association of LRM with excavation from depth shows that the carbon in LRM is native to the planet, rather than deposited over time by impacts.

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“…The first hypothesis is consistent with the absence of spectral evidence for sulfide minerals in surface rocks (McClintock et al, 2008;Izenberg et al, 2014) while the second could explain the correlations between S and Ca-Mg observed in Mercurian lavas . Understanding the origin of high sulfur concentrations at the surface of Mercury is important to better constrain the structure of the planet and the distribution of sulfur amongst the different reservoirs (mantle, core and crust), the mechanisms of explosive volcanism (Kerber et al, 2009;Thomas et al, 2014a;Weider et al, 2016), and the formation of the hollows (sub-kilometer scale shallow depressions surrounded by bright deposits) which may have formed during sublimation of volatiles (Blewett et al, 2013;Thomas et al, 2014b).…”

Section: Introductionmentioning

confidence: 99%

Sulfur solubility in reduced mafic silicate melts: Implications for the speciation and distribution of sulfur on Mercury

Namur

Charlier

Holtz

et al. 2016

Earth and Planetary Science Letters

118

160

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Chemical data from the MESSENGER spacecraft revealed that surface rocks on Mercury are unusually enriched in sulfur compared to samples from other terrestrial planets. In order to understand the speciation and distribution of sulfur on Mercury, we performed high temperature (1200-1750 • C), lowto high-pressure (1 bar to 4 GPa) experiments on compositions representative of Mercurian lavas and on the silicate composition of an enstatite chondrite. We equilibrated silicate melts with sulfide and metallic melts under highly reducing conditions (IW-1.5 to IW-9.4; IW = iron-wüstite oxygen fugacity buffer). Under these oxygen fugacity conditions, sulfur dissolves in the silicate melt as S 2− and forms complexes with Fe 2+ , Mg 2+ and Ca 2+ . The sulfur concentration in silicate melts at sulfide saturation (SCSS) increases with increasing reducing conditions (from <1 wt.% S at IW-2 to >10 wt.% S at IW-8) and with increasing temperature. Metallic melts have a low sulfur content which decreases from 3 wt.% at IW-2 to 0 wt.% at IW-9. We developed an empirical parameterization to predict SCSS in Mercurian magmas as a function of oxygen fugacity ( f O 2 ), temperature, pressure and silicate melt composition. SCSS being not strictly a redox reaction, our expression is fully valid for magmatic systems containing a metal phase. Using physical constraints of the Mercurian mantle and magmas as well as our experimental results, we suggest that basalts on Mercury were free of sulfide globules when they erupted. The high sulfur contents revealed by MESSENGER result from the high sulfur solubility in silicate melt at reducing conditions. We make the realistic assumption that the oxygen fugacity of mantle rocks was set during equilibration of the magma ocean with the core and/or that the mantle contains a minor metal phase and combine our parameterization of SCSS with chemical data from MESSENGER to constrain the oxygen fugacity of Mercury's interior to IW-5.4 ± 0.4. We also calculate that the mantle of Mercury contains 7-11 wt.% S and that the metallic core of the planet has little sulfur (<1.5 wt.% S). The external part of the Mercurian core is likely to be made up of a thin (<90 km) FeS layer.

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Long‐lived explosive volcanism on Mercury

Cited by 79 publications

References 46 publications

Spectroscopic properties of explosive volcanism within the Caloris basin with MESSENGER observations

Spectroscopic properties of explosive volcanism within the Caloris basin with MESSENGER observations

Global Distribution and Spectral Properties of Low‐Reflectance Material on Mercury

Sulfur solubility in reduced mafic silicate melts: Implications for the speciation and distribution of sulfur on Mercury

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