An investigation of the bluish material on Ceres

Stephan, K.; Jaumann, R.; Krohn, Katrin; Schmedemann, N.; Zambon, F.; Tosi, F.; Carrozzo, F. G.; McFadden, L. A.; Otto, Katharina A.; Sanctis, M. C. De; Ammannito, E.; Matz, Klaus-Dieter; Preusker, Frank; Raymond, C. A.; Russell, C. T.

doi:10.1002/2016gl071652

Cited by 35 publications

(47 citation statements)

References 37 publications

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“…ADM crater ages range from < 6 Ma for Haulani to 110 ± 7.2 Ma for Urvara and 420 ± 60 Ma for Ernutet, the two oldest craters with floor faculae Pasckert et al, 2017 ). FC color images show that the floor facula craters occur in spectrally blue regions, which have a negative spectral slope over the visible wavelengths relative to the JID: YICAR [m5G;November 6, 2017;12:24 ] average surface, consistent with their young age Nathues et al, 2016;Schmedemann et al, 2016;Stephan et al, 2017 ). Floor formation ages of the floor facula craters are known in some cases to be significantly younger than crater formation ages, indicating extensive and sometimes long lasting postimpact activity .…”

Section: Characteristics Of Craters With Floor Faculaementioning

confidence: 87%

The Formation and Evolution of Bright Spots on Ceres

Stein¹,

Ehlmann²,

Palomba³

et al. 2017

Geological Society of America Abstracts With Programs

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a b s t r a c tThe otherwise homogeneous surface of Ceres is dotted with hundreds of anomalously bright, predominantly carbonate-bearing areas, termed "faculae," with Bond albedos ranging from ∼0.02 to > 0.5. Here, we classify and map faculae globally to characterize their geological setting, assess potential mechanisms for their formation and destruction, and gain insight into the processes affecting the Ceres surface and near-surface. Faculae were found to occur in four distinct geological settings, associated predominantly with impact craters: (1) crater pits, peaks, or floor fractures (floor faculae), (2) crater rims or walls (rim/wall faculae), (3) bright ejecta blankets, and (4) the mountain Ahuna Mons. Floor faculae were identified in eight large, deep, and geologically young (asteroid-derived model (ADM) ages of < 420 ± 60 Ma) craters: Occator, Haulani, Dantu, Ikapati, Urvara, Gaue, Ernutet, and Azacca. The geometry and geomorphic features of the eight craters with floor faculae are consistent with facula formation via impact-induced heating and upwelling of volatile-rich materials, upwelling/excavation of heterogeneously distributed subsurface brines or their precipitation products, or a combination of both processes. Rim/wall faculae and bright ejecta occur in and around hundreds of relatively young craters of all sizes, and the geometry of exposures is consistent with facula formation via the excavation of subsurface bright material, possibly from floor faculae that were previously emplaced and buried. A negative correlation between rim/wall facula albedo and crater age indicates that faculae darken over time. Models using the Ceres crater production function suggest initial production or exposure of faculae by large impacts, subsequent dissemination of facula materials to form additional small faculae, and then burial by impact-induced lateral mixing, which destroys faculae over timescales of less than 1.25 Gyr. Cumulatively, these models and the observation of faculae limited to geologically young craters indicate relatively modern formation or exposure of faculae, indicating that Ceres' surface remains active and that the near surface may support brines in the present day.

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Section: Characteristics Of Craters With Floor Faculaementioning

confidence: 87%

The Formation and Evolution of Bright Spots on Ceres

Stein¹,

Ehlmann²,

Palomba³

et al. 2017

Geological Society of America Abstracts With Programs

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“…Space weathering may be responsible for the fading of the blue color over time. Alternative explanations for the blue color are explored by Stephan et al (2016).…”

Section: Discussionmentioning

confidence: 99%

Resolved spectrophotometric properties of the Ceres surface from Dawn Framing Camera images

Schröder

Mottola

Carsenty

et al. 2017

Icarus

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100

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We present a global spectrophotometric characterization of the Ceres surface using Dawn Framing Camera (FC) images. We identify the photometric model that yields the best results for photometrically correcting images. Corrected FC images acquired on approach to Ceres were assembled into global maps of albedo and color. Generally, albedo and color variations on Ceres are muted. The albedo map is dominated by a large, circular feature in Vendimia Planitia, known from HST images (Li et al., 2006), and dotted by smaller bright features mostly associated with fresh-looking craters. The dominant color variation over the surface is represented by the presence of "blue" material in and around such craters, which has a negative spectral slope over the visible wavelength range when compared to average terrain. We also mapped variations of the phase curve by employing an exponential photometric model, a technique previously applied to asteroid Vesta . The surface of Ceres scatters light differently from Vesta in the sense that the ejecta of several fresh-looking craters may be physically smooth rather than rough. High albedo, blue color, and physical smoothness all appear to be indicators of youth. The blue color may result from the desiccation of ejected material that is similar to the phyllosilicates/water ice mixtures in the experiments of Poch et al. (2016). The physical smoothness of some blue terrains would be consistent with an initially liquid condition, perhaps as a consequence of impact melting of subsurface water ice. We find red terrain (positive spectral slope) near Ernutet crater, where De Sanctis et al. (2017) detected organic material. The spectrophotometric properties of the large Vendimia Planitia feature suggest it is a palimpsest, consistent with the Marchi et al. (2016) impact basin hypothesis. The central bright area in Occator crater, Cerealia Facula, is the brightest on Ceres with an average visual normal albedo of about 0.6 at a resolution of 1.3 km per pixel (six times Ceres average). The albedo of fresh, bright material seen inside this area in the highest resolution images (35 m per pixel) is probably around unity. Cerealia Facula has an unusually steep phase function, which may be due to unresolved topography, high surface roughness, or large average particle size. It has a strongly red spectrum whereas the neighboring, less-bright, Vinalia Faculae are neutral in color. We find no evidence for a diurnal ground fog-type haze in Occator as described by Nathues et al. (2015). We can neither reproduce their findings using the same images, nor confirm them using higher resolution images. FC images have not yet offered direct evidence for present sublimation in Occator.

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“…in which 1/β represents the radar photon's mean-free path; β is a function of the number density n b (bubbles m −3 ) and of the bubbles Mie's cross section σ Mie : β = n b σ Mie . The flux leaving the sea and returning to the RADAR is I out = (1 − R in )I ↑,τ =0 , here, the reflectance R in of the interface sea atmosphere, is assumed to take into account the effect of the rugosity (Grima et al 2017), which is usually, except in the occurrence of a "Magic Island" event, measured to be very small (Wye et al 2009;Zebker et al 2014;Grima et al 2017;Stephan et al 2010;Barnes et al 2011).…”

Section: Bubbles Radar Signaturementioning

confidence: 99%

Bubbles in Titan’s Seas: Nucleation, Growth, and RADAR Signature

Cordier

Liger-Belair

2018

ApJ

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In the polar regions of Titan, the main satellite of Saturn, hydrocarbon seas have been discovered by the Cassini-Huygens mission. RADAR observations have revealed surprising and transient bright areas over Ligeia Mare surface. As suggested by recent research, bubbles could explain these strange features. However, the nucleation and growth of such bubbles, together with their RADAR reflectivity, have never been investigated. All of these aspects are critical to an actual observation. We have thus applied the classical nucleation theory to our context, and we developed a specific radiative transfer model that is appropriate for bubbles streams in cryogenic liquids. According to our results, the sea bed appears to be the most plausible place for the generation of bubbles, leading to a signal comparable to observations. This conclusion is supported by thermodynamic arguments and by RADAR properties of a bubbly column. The latter are also valid in the case of bubble plumes, due to gas leaking from the sea floor.

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An investigation of the bluish material on Ceres

Cited by 35 publications

References 37 publications

The Formation and Evolution of Bright Spots on Ceres

The Formation and Evolution of Bright Spots on Ceres

Resolved spectrophotometric properties of the Ceres surface from Dawn Framing Camera images

Bubbles in Titan’s Seas: Nucleation, Growth, and RADAR Signature

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