Dawn arrives at Ceres: Exploration of a small, volatile-rich world

Russell, C. T.; Raymond, C. A.; Ammannito, E.; Buczkowski, D. L.; Sanctis, M. C. De; Hiesinger, H.; Jaumann, R.; Konopliv, A. S.; McSween, H. Y.; Nathues, A.; Park, R. S.; Pieters, C. M.; Prettyman, T. H.; McCord, T. B.; McFadden, L. A.; Mottola, S.; Zuber, M. T.; Joy, S. P.; Polanskey, C.; Rayman, Marc D.; Castillo‐Rogez, Julie; J., P.; Combe, Jean-Philippe; Ermakov, A.; Fu, R. R.; Hoffmann, M.; Jia, Y. D.; King, Scott D.; Lawrence, D. J.; Li, J.-Y.; Marchi, S.; Preusker, Frank; Roatsch, Thomas; Ruesch, O.; Schenk, P.; Villarreal, M. N.; Yamashita, N.

doi:10.1126/science.aaf4219

Cited by 194 publications

(138 citation statements)

References 40 publications

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“…As shown below, this approximation is reasonable in the case of Ceres' surface, which shows small variability at large scale (>1 km). Nonetheless, a number of isolated bright features have been recognized throughout the surface of the body, as also reported by Schröder et al (2017, Russell et al (2016). They show a much higher albedo than the average, which cannot be described by the same set of photometric parameters derived here.…”

Section: Photometric Correction Accuracysupporting

confidence: 76%

Spectrophotometric properties of dwarf planet Ceres from the VIR spectrometer on board the Dawn mission

Ciarniello

Sanctis

Ammannito

et al. 2017

A&A

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Aims. We present a study of the spectrophotometric properties of dwarf planet Ceres in the visual-to-infrared (VIS-IR) spectral range by means of hyper-spectral images acquired by the VIR imaging spectrometer on board the NASA Dawn mission. Methods. Disk-resolved observations with a phase angle within the 7• < α < 132• interval were used to characterize Ceres' phase curve in the 0.465-4.05 µm spectral range. Hapke's model was applied to perform the photometric correction of the dataset to standard observation geometry at VIS-IR wavelength, allowing us to produce albedo and color maps of the surface. The V-band magnitude phase function of Ceres has been computed from disk-resolved images and fitted with both the classical linear model and H-G formalism.Results. The single-scattering albedo and the asymmetry parameter at 0.55 µm are w = 0.14 ± 0.02 and ξ = −0.11 ± 0.08, respectively (two-lobe Henyey-Greenstein phase function); at the same wavelength, Ceres' geometric albedo as derived from our modeling is 0.094 ± 0.007; the roughness parameter isθ = 29• ± 6• . Albedo maps indicate small variability on a global scale with an average reflectance at standard geometry of 0.034 ± 0.003. Nonetheless, isolated areas such as the Occator bright spots, Haulani, and Oxo show an albedo much higher than average. We measure a significant spectral phase reddening, and the average spectral slope of Ceres' surface after photometric correction is 1.1% kÅ • gives H = 3.14 ± 0.04 and G = 0.10 ± 0.04, while the classical linear model provides V(1, 1, 0 • ) = 3.48 ± 0.03 and β = 0.036 ± 0.002. The comparison of our results with spectrophotometric properties of other minor bodies indicates that Ceres has a less back-scattering phase function and a slightly higher albedo than comets and C-type objects. However, the latter represents the closest match in the usual asteroid taxonomy.

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Section: Photometric Correction Accuracysupporting

confidence: 76%

Spectrophotometric properties of dwarf planet Ceres from the VIR spectrometer on board the Dawn mission

Ciarniello

Sanctis

Ammannito

et al. 2017

A&A

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“…This has been remarkably illustrated by fly-by and rendezvous space missions (Belton et al, 1992(Belton et al, , 1996Zuber et al, 2000;Fujiwara et al, 2006;Sierks et al, 2011;Russell et al, 2012Russell et al, , 2016, as well as observations from the Earth (e.g., Carry et al 2008Carry et al , 2010bMerline et al 2013). In the late nineties, observations of (4) Vesta with the Hubble Space Telescope (HST) led to the discovery of the now-called "Rheasilvia basin" and allowed for establishment of the origin of the Vestoids and HED meteorites found on Earth Binzel et al, 1997).…”

Section: Introductionmentioning

confidence: 99%

3D shape of asteroid (6) Hebe from VLT/SPHERE imaging: Implications for the origin of ordinary H chondrites

Marsset

Carry

Dumas

et al. 2017

A&A

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Context. The high-angular-resolution capability of the new-generation ground-based adaptive-optics camera SPHERE at ESO VLT allows us to assess, for the very first time, the cratering record of medium-sized (D∼100-200 km) asteroids from the ground, opening the prospect of a new era of investigation of the asteroid belt's collisional history. Aims. We investigate here the collisional history of asteroid (6) Hebe and challenge the idea that Hebe may be the parent body of ordinary H chondrites, the most common type of meteorites found on Earth (∼34% of the falls). Methods. We observed Hebe with SPHERE as part of the science verification of the instrument. Combined with earlier adaptiveoptics images and optical light curves, we model the spin and three-dimensional (3D) shape of Hebe and check the consistency of the derived model against available stellar occultations and thermal measurements. Results. Our 3D shape model fits the images with sub-pixel residuals and the light curves to 0.02 mag. The rotation period (7.274 47 h), spin (ECJ2000 λ,β of 343 • ,+47 • ), and volume-equivalent diameter (193 ± 6 km) are consistent with previous determinations and thermophysical modeling. Hebe's inferred density is 3.48 ± 0.64 g.cm −3 , in agreement with an intact interior based on its H-chondrite composition. Using the 3D shape model to derive the volume of the largest depression (likely impact crater), it appears that the latter is significantly smaller than the total volume of close-by S-type H-chondrite-like asteroid families. Conclusions. Our results imply that (6) Hebe is not the most likely source of H chondrites. Over the coming years, our team will collect similar high-precision shape measurements with VLT/SPHERE for ∼40 asteroids covering the main compositional classes, thus providing an unprecedented dataset to investigate the origin and collisional evolution of the asteroid belt.

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“…Detection of an atmosphere on Ceres has been reported, but the occurrence is only episodic (A 'Hearn & Feldman 1992;Rousselot et al 2011;Küppers et al 2014;Roth et al 2016). No instrument on the Dawn spacecraft was designed to detect an exosphere, but observations during the initial highest-altitude orbit yielded no evidence of forwardscattered light that a dust-carrying atmosphere would have produced (Russell et al 2016). Evidence of haze on Ceres (Nathues et al 2015;Thangjam et al 2016) is controversial .…”

Section: Introductionmentioning

confidence: 99%

“…Evidence of haze on Ceres (Nathues et al 2015;Thangjam et al 2016) is controversial . However, the detection of energetic electrons on three successive spacecraft orbits after a solar proton event can be interpreted as the by-product of a transient atmosphere (Russell et al 2016;Jia et al 2017;Villarreal et al 2017).…”

Section: Introductionmentioning

confidence: 99%

The Putative Cerean Exosphere

Schörghofer

Byrne

Landis

et al. 2017

ApJ

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The ice-rich crust of dwarf planet 1 Ceres is the source of a tenuous water exosphere, and the behavior of this putative exosphere is investigated with model calculations. Outgassing water molecules seasonally condense around the winter pole in an optically thin layer. This seasonal cap reaches an estimated mass of at least 2 10 kg 3 , and the aphelion summer pole may even retain water throughout summer. If this reservoir is suddenly released by a solar energetic particle event, it would form a denser transient water exosphere. Our model calculations also explore species other than H 2 O. Light exospheric species escape rapidly from Ceres due to its low gravity, and hence their exospheres dissipate soon after their respective source has faded. For example, the theoretical turn-over time in a water exosphere is only 7 hr. A significant fraction of CO 2 and SO 2 molecules can get trapped and stored in perennially shadowed regions at the current spin axis orientation, but not at the higher spin axis tilt, leaving H 2 O as the only common volatile expected to accumulate in polar cold traps over long timescales. The D/H fractionation during migration to the cold traps is only about 10%.

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Dawn arrives at Ceres: Exploration of a small, volatile-rich world

Cited by 194 publications

References 40 publications

Spectrophotometric properties of dwarf planet Ceres from the VIR spectrometer on board the Dawn mission

Spectrophotometric properties of dwarf planet Ceres from the VIR spectrometer on board the Dawn mission

3D shape of asteroid (6) Hebe from VLT/SPHERE imaging: Implications for the origin of ordinary H chondrites

The Putative Cerean Exosphere

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