Low Water Outgassing from (24) Themis and (65) Cybele: 3.1 μm Near-IR Spectral Implications

O’Rourke, L.; Müller, Thomas; Biver, Nicolás; Bockelée‐Morvan, Dominique; Hasegawa, Susumu; Valtchanov, I.; Küppers, M.; Fornasier, S.; Campins, H.; Fujiwara, Hideaki; Teyssier, D.; Lim, T.

doi:10.3847/2041-8213/aba62b

Cited by 7 publications

(3 citation statements)

References 58 publications

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“…Several interpretations have been forwarded for the 3.0-3.2 μm band. In the case of Themis models incorporating very fine water frost (<0.1 μm) coating underlying refractory grains provide a good match (Campins et al 2010;Rivkin & Emery 2010; but see McKay et al 2017;O'Rourke et al 2020 for arguments against this interpretation). Meanwhile, N-H stretch absorption from ammoniated surface species has been hypothesized to be a primary contributor to the feature on Ceres (e.g., King et al 1992;De Sanctis et al 2015).…”

Section: μM Oh Bandmentioning

confidence: 99%

JWST Near-infrared Spectroscopy of the Lucy Jupiter Trojan Flyby Targets: Evidence for OH Absorption, Aliphatic Organics, and CO₂

Wong,

Brown,

Emery

et al. 2024

Planet. Sci. J.

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We present observations obtained with the Near Infrared Spectrograph on JWST of the five Jupiter Trojans that will be visited by the Lucy spacecraft—the Patroclus–Menoetius binary, Eurybates, Orus, Leucus, and Polymele. The measured 1.7–5.3 μm reflectance spectra, which provide increased wavelength coverage, spatial resolution, and signal-to-noise ratio over previous ground-based spectroscopy, reveal several distinct absorption features. We detect a broad OH band centered at 3 μm that is most prominent on the less-red objects Eurybates, Patroclus–Menoetius, and Polymele. An additional absorption feature at 3.3–3.6 μm, indicative of aliphatic organics, is systematically deeper on the red objects Orus and Leucus. The collisional fragment Eurybates is unique in displaying an absorption band at 4.25 μm that we attribute to bound or trapped CO2. Comparisons with other solar system small bodies reveal broad similarities in the 2.7–3.6 μm bands with analogous features on Centaurs, Kuiper Belt objects (KBOs), and the active asteroid 238P. In the context of recent solar system evolution models, which posit that the Trojans initially formed in the outer solar system, the significant attenuation of the 2.7–3.6 μm absorption features on Trojans relative to KBOs may be the result of secondary thermal processing of the Trojans’ surfaces at the higher temperatures of the Jupiter region. The CO2 band manifested on the surface of Eurybates suggests that CO2 may be a major constituent in the bulk composition of Trojans, but resides in the subsurface or deeper interior and is largely obscured by refractory material that formed from the thermophysical processes that were activated during their inward migration.

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Section: μM Oh Bandmentioning

confidence: 99%

JWST Near-infrared Spectroscopy of the Lucy Jupiter Trojan Flyby Targets: Evidence for OH Absorption, Aliphatic Organics, and CO₂

Wong,

Brown,

Emery

et al. 2024

Planet. Sci. J.

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“…For Themis, radiative-transfer models indicate that a 3 μm band without corresponding short-wavelength ice absorption features can be explained by a mixture of carbonaceous (low-albedo) grains and pyroxene grains, the latter coated with a thin 10–100 nm layer of water ice 18 . However, this interpretation has since been challenged by measurements that place sensitive upper limits to water production rates for this object, ruling out surface water ice as the cause of its 3 μm band 19 , 20 .…”

Section: Mainmentioning

confidence: 99%

Spectroscopic identification of water emission from a main-belt comet

Kelley

Hsieh

Bodewits

et al. 2023

Nature

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Main-belt comets are small Solar System bodies located in the asteroid belt that repeatedly exhibit comet-like activity (that is, dust comae or tails) during their perihelion passages, strongly indicating ice sublimation1,2. Although the existence of main-belt comets implies the presence of extant water ice in the asteroid belt, no gas has been detected around these objects despite intense scrutiny with the world’s largest telescopes3. Here we present James Webb Space Telescope observations that clearly show that main-belt comet 238P/Read has a coma of water vapour, but lacks a significant CO2 gas coma. Our findings demonstrate that the activity of comet Read is driven by water–ice sublimation, and implies that main-belt comets are fundamentally different from the general cometary population. Whether or not comet Read experienced different formation circumstances or evolutionary history, it is unlikely to be a recent asteroid belt interloper from the outer Solar System. On the basis of these results, main-belt comets appear to represent a sample of volatile material that is currently unrepresented in observations of classical comets and the meteoritic record, making them important for understanding the early Solar System’s volatile inventory and its subsequent evolution.

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“…However, this claim currently remains a matter of debate (e.g. Beck et al 2011;O'Rourke et al 2020).…”

Section: Introductionmentioning

confidence: 99%

The equilibrium shape of (65) Cybele: primordial or relic of a large impact?

Marsset

Brož

Vermersch

et al. 2023

A&A

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Context. Cybele asteroids constitute an appealing reservoir of primitive material genetically linked to the outer Solar System, and the physical properties (size and shape) of the largest members can be readily accessed by large (8m class) telescopes. Aims. We took advantage of the bright apparition of the most iconic member of the Cybele population, (65) Cybele, in July and August 2021 to acquire high-angular-resolution images and optical light curves of the asteroid with which we aim to analyse its shape and bulk properties. Methods. Eight series of images were acquired with VLT/SPHERE+ZIMPOL, seven of which were combined with optical light curves to reconstruct the shape of the asteroid using the ADAM, MPCD, and SAGE algorithms. The origin of the shape was investigated by means of N-body simulations.Results. Cybele has a volume-equivalent diameter of 263± 3 km and a bulk density of 1.55 ± 0.19 g.cm −3 . Notably, its shape and rotation state are closely compatible with those of a Maclaurin equilibrium figure. The lack of a collisional family associated with Cybele and the higher bulk density of that body with respect to other large P-type asteroids suggest that it never experienced any large disruptive impact followed by rapid re-accumulation. This would imply that its present-day shape represents the original one. However, numerical integration of the long-term dynamical evolution of a hypothetical family of Cybele shows that it is dispersed by gravitational perturbations and chaotic diffusion over gigayears of evolution. Conclusions. The very close match between Cybele and an equilibrium figure opens up the possibility that D ≥ 260 km (M ≥ 1.5 × 10 19 kg) small bodies from the outer Solar System all formed at equilibrium. However, we cannot currently rule out an old impact as the origin of the equilibrium shape of Cybele. Cybele itself is found to be dynamically unstable, implying that it was 'recently' (<1 Gyr ago) placed on its current orbit either through slow diffusion from a relatively stable orbit in the Cybele region or, less likely, from an unstable, Jupiter-family-comet orbit in the planet-crossing region.Based on observations made with ESO Telescopes at the Paranal Observatory under programme ID 107.22QN.001 (PI: M. Marsset)Reduced and deconvolved images listed in Table A.

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Low Water Outgassing from (24) Themis and (65) Cybele: 3.1 μm Near-IR Spectral Implications

Cited by 7 publications

References 58 publications

JWST Near-infrared Spectroscopy of the Lucy Jupiter Trojan Flyby Targets: Evidence for OH Absorption, Aliphatic Organics, and CO₂

JWST Near-infrared Spectroscopy of the Lucy Jupiter Trojan Flyby Targets: Evidence for OH Absorption, Aliphatic Organics, and CO₂

Spectroscopic identification of water emission from a main-belt comet

The equilibrium shape of (65) Cybele: primordial or relic of a large impact?

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Low Water Outgassing from (24) Themis and (65) Cybele: 3.1 μm Near-IR Spectral Implications

Cited by 7 publications

References 58 publications

JWST Near-infrared Spectroscopy of the Lucy Jupiter Trojan Flyby Targets: Evidence for OH Absorption, Aliphatic Organics, and CO2

JWST Near-infrared Spectroscopy of the Lucy Jupiter Trojan Flyby Targets: Evidence for OH Absorption, Aliphatic Organics, and CO2

Spectroscopic identification of water emission from a main-belt comet

The equilibrium shape of (65) Cybele: primordial or relic of a large impact?

Contact Info

Product

Resources

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JWST Near-infrared Spectroscopy of the Lucy Jupiter Trojan Flyby Targets: Evidence for OH Absorption, Aliphatic Organics, and CO₂

JWST Near-infrared Spectroscopy of the Lucy Jupiter Trojan Flyby Targets: Evidence for OH Absorption, Aliphatic Organics, and CO₂