Spectral behavior of sulfides in simulated daytime surface conditions of Mercury: Supporting past (MESSENGER) and future missions (BepiColombo)

Varatharajan, Indhu; Maturilli, Alessandro; Helbert, J.; Alemanno, Giulia; Hiesinger, H.

doi:10.1016/j.epsl.2019.05.020

Cited by 23 publications

(44 citation statements)

References 17 publications

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“…The destruction of nanophase sulfides increases the reflectance and decreases the spectral slope and that could explain why hollow interiors have higher reflectance and less steep VISNIR‐slope than parent material (crater floor). In addition, as mentioned in Section 3.2, the particular spectral properties of hollows may be related to the presence of an absorption band centered around 300 nm associated with the sulfides CaS, NaS, and MgS (Varatharajan et al., 2019). The results shown in Figure 13 are consistent with the loss of sulfides progressively decreasing the depth of the absorption band, and thus decreasing the UV‐downturn and curvature during the hollow formation.…”

Section: Discussionmentioning

confidence: 99%

“…NaS shows stronger UV spectral features (Varatharajan et al, 2019). In consequence, the spectral features of CaS, MgS, and NaS, even under the temperature conditions of Mercury, may involve the high UV-downturn of the hollows.…”

Section: Near-uv Properties and Spectral Curvature As Diagnostic Of Hmentioning

confidence: 96%

“…(2013) showed that the thermal processing at Mercury daytime temperature reduces the spectral contrast of the diagnostic features of sulfides around 600 nm. In addition, recent laboratory measurements under MASCS observing conditions show that the sulfides (fresh or heated) proposed in Section 3.2 (CaS, NaS, and one MgS sample), to explain the high values of UV‐downturn in hollows spectra, do not exhibit absorption bands in the visible range (Varatharajan et al., 2019).…”

Section: Investigation Of Absorption Bands In Hollowsmentioning

confidence: 99%

“…Laboratory measurements carried out under the conditions of MASCS observations show that the spectra of fresh CaS, NaS, and MgS (two samples) have a strong absorption band between 280 and 350 nm, centered at 300 nm (Varatharajan et al., 2019). The Mercury daytime temperatures have different implications on the spectral features of these samples (Varatharajan et al., 2019). For one of the MgS sample, the absorption features disappear after the thermal processing at Mercury's surface temperatures.…”

Section: Spectral Properties Of Hollows From Near‐uv To Nirmentioning

confidence: 99%

“…For one of the MgS sample, the absorption features disappear after the thermal processing at Mercury's surface temperatures. The spectral contrast of the absorption features around 300 nm is slightly subdued for the heated CaS and the second heated MgS sample, while the heated NaS shows stronger UV spectral features (Varatharajan et al., 2019). In consequence, the spectral features of CaS, MgS, and NaS, even under the temperature conditions of Mercury, may involve the high UV‐downturn of the hollows.…”

Section: Spectral Properties Of Hollows From Near‐uv To Nirmentioning

confidence: 99%

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Near‐Ultraviolet to Near‐Infrared Spectral Properties of Hollows on Mercury: Implications for Origin and Formation Process

et al. 2020

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Section: Discussionmentioning

confidence: 99%

Section: Near-uv Properties and Spectral Curvature As Diagnostic Of Hmentioning

confidence: 96%

Section: Investigation Of Absorption Bands In Hollowsmentioning

confidence: 99%

Section: Spectral Properties Of Hollows From Near‐uv To Nirmentioning

confidence: 99%

Section: Spectral Properties Of Hollows From Near‐uv To Nirmentioning

confidence: 99%

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Near‐Ultraviolet to Near‐Infrared Spectral Properties of Hollows on Mercury: Implications for Origin and Formation Process

et al. 2020

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Anharmonic effects on the reflectivity of CaS and MgS: a first-principles based study

Chmeruk¹,

Núñez-Valdez²

2023

Appl. Phys. A

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We employ systematic calculations based on density functional theory to model the reflectivity of CaS and MgS in the infrared region. We show that in addition to the modeling using the harmonic approximation, an accurate spectral description requires the inclusion of anharmonic effects. Due to their conceptual simplicity, CaS and MgS are excellent systems for the explicit consideration of the anharmonicity, which we include here using a perturbative approach up to three-phonon scattering processes, and the consideration of isotopic disorder. All physical quantities, such as Born effective charges and dielectric constant, necessary for the calculation of the reflectivity within the Lorentz model are extracted from our first-principles computations. To validate our predicted optical and transversal modes, and reflectivity spectra, we compare them to available experimental results. We find that the overall agreement is good, which supports the importance of the inclusion of anharmonic terms in the modeling of optical properties in the infrared region.

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Rationale for BepiColombo Studies of Mercury’s Surface and Composition

et al. 2020

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BepiColombo has a larger and in many ways more capable suite of instruments relevant for determination of the topographic, physical, chemical and mineralogical properties of Mercury’s surface than the suite carried by NASA’s MESSENGER spacecraft. Moreover, BepiColombo’s data rate is substantially higher. This equips it to confirm, elaborate upon, and go beyond many of MESSENGER’s remarkable achievements. Furthermore, the geometry of BepiColombo’s orbital science campaign, beginning in 2026, will enable it to make uniformly resolved observations of both northern and southern hemispheres. This will offer more detailed and complete imaging and topographic mapping, element mapping with better sensitivity and improved spatial resolution, and totally new mineralogical mapping. We discuss MESSENGER data in the context of preparing for BepiColombo, and describe the contributions that we expect BepiColombo to make towards increased knowledge and understanding of Mercury’s surface and its composition. Much current work, including analysis of analogue materials, is directed towards better preparing ourselves to understand what BepiColombo might reveal. Some of MESSENGER’s more remarkable observations were obtained under unique or extreme conditions. BepiColombo should be able to confirm the validity of these observations and reveal the extent to which they are representative of the planet as a whole. It will also make new observations to clarify geological processes governing and reflecting crustal origin and evolution. We anticipate that the insights gained into Mercury’s geological history and its current space weathering environment will enable us to better understand the relationships of surface chemistry, morphologies and structures with the composition of crustal types, including the nature and mobility of volatile species. This will enable estimation of the composition of the mantle from which the crust was derived, and lead to tighter constraints on models for Mercury’s origin including the nature and original heliocentric distance of the material from which it formed.

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Spectral behavior of sulfides in simulated daytime surface conditions of Mercury: Supporting past (MESSENGER) and future missions (BepiColombo)

Cited by 23 publications

References 17 publications

Near‐Ultraviolet to Near‐Infrared Spectral Properties of Hollows on Mercury: Implications for Origin and Formation Process

Near‐Ultraviolet to Near‐Infrared Spectral Properties of Hollows on Mercury: Implications for Origin and Formation Process

Anharmonic effects on the reflectivity of CaS and MgS: a first-principles based study

Rationale for BepiColombo Studies of Mercury’s Surface and Composition

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