Low-temperature reflectance spectra of brucite and the primitive surface of 1-Ceres?

Beck, Pierre; Schmitt, Bernard; Cloutis, E. A.; Vernazza, Pierre

doi:10.1016/j.icarus.2015.05.031

Cited by 14 publications

(10 citation statements)

References 45 publications

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“…The clays produced by our model tend to be richer in Mg than Fe, although Fe-rich cronstedtite replaces magnetite as the dominant Fe mineral at low T in simulations with initial pure water. The presence of saponite and NH 4 -clays rather than brucite may be consistent with recent (and previous) interpretations of Ceres's 3.06 μm feature [Beck et al, 2015;King et al, 1992]. Carbonates, which seem prominent on Ceres [Rivkin et al, 2012], are absent from our equilibrium mineral assemblages, but present in some equilibrium solutions from which they could precipitate upon solution freezing or vaporization.…”

Section: Geochemistrysupporting

confidence: 90%

“…Other lines of evidence argue against a pure ice mantle. Ceres's surface is dark and uniform (albedo 0.04 to 0.09) [ Li et al , ], with spectra consistent with minerals resulting from aqueous alteration [ Lebofsky et al , ; Rivkin et al , ], possibly brucite, magnetite, carbonates (magnesite), and phyllosilicates (cronstedtite or saponites) [ King et al , ; Milliken and Rivkin , ; Rivkin et al , ; Beck et al , ]. Ceres's unique surface composition argues against exogenous sources such as meteoritic infall or formation from the observed surface material (as Zolotov [] suggests), unless the observed minerals formed out of fluid‐rock equilibrium in transient near‐surface fluids generated by chondritic impactors [ Zolotov , ].…”

Section: Introductionmentioning

confidence: 99%

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Geochemistry, thermal evolution, and cryovolcanism on Ceres with a muddy ice mantle

Neveu

Desch

2015

Geophysical Research Letters

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We present a model of the internal evolution of Ceres consistent with pre‐Dawn observations and preliminary data returned by Dawn. We assume that Ceres accreted ice and both micron‐ and millimeter‐sized rock particles and that micron‐sized fines stayed suspended in liquid during differentiation. We conclude that aqueously altered grains were emplaced on Ceres's surface during the first tens of megayears of its evolution. Our geochemical simulations suggest that Ceres's unusual surface mineralogy is consistent with aqueous alteration of CM material, possibly by NH3‐bearing fluid. Thermal evolution simulations including insulating fines yield present‐day liquid at depth if Ceres has a small core or no core at all; otherwise, they yield temperatures at the core‐mantle boundary of 240–250 K, just warm enough for chloride brines to persist and be freezing today. We hypothesize that ongoing freezing may overpressurize liquid or briny reservoirs, driving cryovolcanic outflow whose surface expression may have been observed by Dawn at Ceres's “bright spots.” These outflows may contribute to the water vapor being produced at Ceres.

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Section: Geochemistrysupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Geochemistry, thermal evolution, and cryovolcanism on Ceres with a muddy ice mantle

Neveu

Desch

2015

Geophysical Research Letters

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“…Our numerical model computes compaction of porous material and is, thus, very well suited to investigate the scenario proposed by Zolotov (2009). Furthermore, based on both previous observations by the Hubble Space Telescope (e.g., Carry et al 2008) and recent ones by Dawn (e.g., Beck et al 2015), minerals involved in the compositions adopted here are most probably present on Ceres and have played an important role in its evolution. The exact abundances of these minerals are not certain, however.…”

Section: Modelmentioning

confidence: 87%

“…On the other hand, a low-density phase, such as water ice, represents yet another explanation of Ceres' density and is no less plausible. In particular, based on the recent observations by the Dawn mission (see, e.g., Schenk et al 2015;Beck et al 2015), both water ice and hydrated minerals could be present on Ceres. Assuming that minerals involved in CIa and CIb probably played an important role in the evolution of Ceres, we envision an augmentation of the current model by considering water as an additional phase and water-rock differentiation.…”

Section: Discussionmentioning

confidence: 98%

Modelling the internal structure of Ceres: Coupling of accretion with compaction by creep and implications for the water-rock differentiation

Neumann

Breuer

Spohn

2015

A&A

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Aims. We model the compaction of a Ceres-like body that accretes from the protoplanetary dust as a porous aggregate. To do this, we use a comprehensive numerical model in which the accretion starts with a km-size seed and the final radius reaches ≈500 km. Our goal is to investigate the interplay of accretion and loss of porosity by hot pressing. We draw conclusions for the evolution of the porosity profile and the present-day porosity distribution on Ceres. In particular, we test the hypothesis that Ceres' low density can be explained by a porous interior instead of by the presence of ice, and whether compaction occurs due to creep or due to dehydration of hydrated minerals. Methods. We extended our thermal evolution model from previous studies to model compaction of an accreting asteroid that is initially porous. We considered two different compositions of Ceres suggested by other workers. The porosity change was calculated according to the thermally activated creep flow. Depending on the composition, parameters relevant for compaction were changed self-consistently with the mineral phases. Results. We find that compaction of initially porous Ceres is dominated by creep and only slightly perturbed by the dehydration. In particular, dehydration alone cannot lead to compaction because creep can occur before the dehydration. Depending on the accretion duration, timing of the compaction varies from between a few million years and more than one billion years. Thereby, late accretion cannot prevent compaction to an average porosity of <2.5%. We provide the evolution as well as the present-day porosity and temperature profiles for Ceres. The temperature allows for the existence of liquid water in the interior of Ceres at a depths of ≥5−33 km. Depending on the composition, either iron melt is produced regardless of the accretion timing or only for an accretion within the first 4 Ma relative to calcium-aluminium-rich inclusions. This argues for a small metallic core.

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“…Low-temperature reflectance spectra are acquired using SHINE coupled with the double environmental chamber CarboN-IR (Beck et al 2015;Grisolle et al 2014 reduces the thermal gradient inside the meteorite but needs two sapphire windows to close the outer and inner cells. The light passing through these two windows creates reflections between the sample and the inner cell window, but also between the windows themselves.…”

Section: Reflectance Spectroscopy Under Asteroidal Conditionsmentioning

confidence: 99%

Some things special about NEAs: Geometric and environmental effects on the optical signatures of hydration

Potin

Beck

Schmitt

et al. 2019

Icarus

Self Cite

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Here were report on a laboratory study aiming to reproduce specificities of near-Earth Asteroid. We study how the elevated surface temperature, their surface roughness (rock or regolith), as well as observation geometry can affect the absorption features detected on asteroids. For that purpose, we selected a recent carbonaceous chondrite fall, the Mukundpura CM2 chondrite which fell in India in June 2017. Bidirectional reflectance spectroscopy was performed to analyze the effect of the geometrical configuration (incidence, emergence and azimuth angle) on the measurement. Our results show that reflectance spectra obtained under warm environment (NEA-like) tends to show shallower absorption bands compared to low-temperature conditions (MBA-like), but still detectable in our experiments under laboratory timescales.Irreversible alteration of the sample because of the warm environment (from room temperature to 250°C) has been detected as an increase of the spectral slope and a decrease of the band depths (at 0.7µm, 0.9µm and 2.7µm). Comparing the meteoritic chip and the powdered sample, we found that surface texture strongly affects the shape of the reflectance spectra of meteorites and thus of asteroids, where a dust-covered surface presents deeper absorption features. We found that all spectral parameters, such as the reflectance value, spectral slope and possible absorption bands are affected by the geometry of measurement. We observed the disappearance of the 0.7 µm absorption feature at phase angle larger than 120°, but the 3µm band remains detectable on all measured spectra.the 700 nm and 900 nm bands. Acquisitions are set from room temperature (294 K) to 510K every 20K during the increase of temperature, and from 490K to room temperature every 40K when the cell is cooling down. The illumination is fixed at nadir, and the observation at 30°.

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Low-temperature reflectance spectra of brucite and the primitive surface of 1-Ceres?

Cited by 14 publications

References 45 publications

Geochemistry, thermal evolution, and cryovolcanism on Ceres with a muddy ice mantle

Geochemistry, thermal evolution, and cryovolcanism on Ceres with a muddy ice mantle

Modelling the internal structure of Ceres: Coupling of accretion with compaction by creep and implications for the water-rock differentiation

Some things special about NEAs: Geometric and environmental effects on the optical signatures of hydration

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