The lifecycle of hollows on Mercury: An evaluation of candidate volatile phases and a novel model of formation

Phillips, Michael S.; Moersch, Jeffrey E.; Viviano, C. E.; Emery, Joshua P.

doi:10.1016/j.icarus.2021.114306

Cited by 8 publications

(9 citation statements)

References 167 publications

(388 reference statements)

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“…Our detailed analysis of the different facies in the hollows within the Eminescu crater suggests that the bright halo is the most enriched facies in sulfur-bearing minerals. This result is consistent with reprecipitation and/or remobilization of sulfides in the bright halo as proposed in ( 13 , 14 , 23 , 29 ). Moreover, Wang et al .…”

Section: Discussionsupporting

confidence: 92%

“…In literature, the most common candidates for hollow-forming materials are sulfides [e.g., ( 1 – 3 , 7 , 9 , 10 , 14 , 17 – 20 )] due to the high abundance of sulfur at Mercury’s surface [e.g., ( 21 , 22 )]. Thermal modeling suggests that the hollow-forming phase may have been produced through the thermal decomposition of sulfides within LRM ( 23 ), the major spectral unit thought to be spatially associated with the hollows ( 4 , 7 , 23 ). Composition and spectroscopic data revealed that LRM may be enriched with as much as 4 wt % of carbon over the local mean ( 8 , 24 ).…”

Section: Resultsmentioning

confidence: 99%

“…Then, chemical reactions are also proposed to explain the high reflectance of the hollow bright halo ( 2 , 3 ). Thermal modeling ( 23 ) and experimental studies ( 29 ) show that chemical reactions can lead to collapse, remobilization, and/or (re-)precipitation of sulfides at the surface along hollow rim and floor. Our detailed analysis of the different facies in the hollows within the Eminescu crater suggests that the bright halo is the most enriched facies in sulfur-bearing minerals.…”

Section: Discussionmentioning

confidence: 99%

“…S5). If LRMs are the parent material of the hollows and are enriched in sulfides ( 4 , 7 , 23 ), then the spectra used as reference (background material) for the spectral modeling should already contain a larger proportion of sulfides than the spectra used for the hollows not associated with LRM (Eminescu and Tyagaraja). Therefore, the sulfide enrichment in the hollows of the Hopper and Warhol impact craters should be inferior to those measured in the hollows of the Eminescu and Tyagaraja impact craters.…”

Section: Discussionmentioning

confidence: 99%

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Low sulfide concentration in Mercury’s smooth plains inhibits hollows

2023

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MESSENGER (Mercury, Surface, Space Environment, Geochemistry, and Ranging) mission to Mercury led to the discovery of hollows. These geological landforms have no close counterpart on other airless silicate bodies. Multispectral images and geochemical measurements by MESSENGER suggest that hollows are formed by the loss of volatile-bearing minerals. We investigated the mineralogical composition of the hollows using near-ultraviolet to near-infrared spectra obtained by MESSENGER. We compared reflectance spectra of hollows with laboratory spectra of Mercury’s analogs: sulfides, chlorides, silicates, and graphite. The best candidates to reproduce the curvature of the hollow spectra are calcium sulfide, magnesium sulfide, and sodium sulfide. In addition, we performed spectral modeling with spectra obtained at the highest spectral and spatial resolution within the hollows. Our results show that the enrichment of sulfides in hollow material is up to two times higher than the sulfide concentration derived from chemical measurements of Mercury’s high-reflectance smooth plains. This result explains the small percentage of hollows found within these plains.

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Section: Discussionsupporting

confidence: 92%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Low sulfide concentration in Mercury’s smooth plains inhibits hollows

2023

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“…Destabilization of graphite in the harsh surface environment of Mercury might have supported the formation of hollows 14,15 , and assimilation of sulfur and/or carbon from crustal rocks by ascending magma may have driven the explosive volcanism 3,[16][17][18] . Alternatively, other volatile species, such as chlorides 19 and sulfides [20][21][22] , were also proposed to be hollow-forming materials. The debating interpretations of hollow-forming materials (e.g., graphite, chlorides and sulfides) were all largely based on a rather weak absorption feature at the wavelength of ca.…”

mentioning

confidence: 99%

Dark spots on Mercury show no signs of weathering during 30 Earth months

Wang

Xiao

et al. 2022

Commun Earth Environ

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Dark spots on Mercury are recently-formed thin and low-reflectance materials that are related with volatile activity and supposed to be much shorter-lived than their central hollows. Containing unique information about the possible building blocks of Mercury, dark spots have unresolved darkening phases, formation mechanism, and lifetime. Here we investigated reflectance spectra, sub-resolution roughness, and temporal changes of dark spots using the full-mission dataset of MESSENGER. We find that dark spots have the highest concentration of graphite and an intense outgassing origin. Temporal imaging for dark spots reveals no detectable reflectance changes in 30 Earth months, and possibly over 40 Earth years. These observations demonstrate that thermally unstable sulfides such as MgS and CaS are not the major components in dark spots. Possible reflectance changes of dark spots may occur at much longer time scales, providing a reference for modeling the spectral behavior of graphite caused by space weathering on Mercury.

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