Red material on the large moons of Uranus: Dust from the irregular satellites?

Cartwright, Richard; Emery, Joshua P.; Pinilla-Alonso, N.; Lucas, Michael P.; Rivkin, A. S.; Trilling, David E.

doi:10.1016/j.icarus.2018.06.004

Cited by 46 publications

(114 citation statements)

References 79 publications

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“…We analyzed new IRAC Ch.1 and Ch.2 geometric albedos to test the hypothesis that the surfaces of the classical Uranian satellites are mantled by tiny H2O ice grains. Radiative transfer modeling of these new data support the ubiquitous presence of tiny H2O ice grains (≤ 2 µm diameters), consistent with previous analyses of other long NIR datasets (~3 -5 µm; Cartwright et al, 2015Cartwright et al, , 2018. Furthermore, our results indicate that these moons have higher IRAC albedos on their trailing hemispheres compared to their leading hemispheres (except for Miranda), suggesting larger abundances of tiny H2O ice grains and/or less H2O ice is exposed on their trailing sides.…”

Section: Discussionsupporting

confidence: 90%

“…Therefore, the synthetic spectra presented here suggest that the Uranian satellites' regoliths are primarily composed of tiny H2O ice grains (~1 -2 µm diameters). The prevalence of 1 to 2 µm diameter H2O grains is consistent with previous spectral modeling efforts (Cartwright et al, , 2018. We explore how the surfaces of these moons might have developed thin mantles of tiny H2O ice grains in section 4.2.…”

Section: Best Fit Synthetic Spectrasupporting

confidence: 77%

“…If heliocentric dust collisions are driving the leading/trailing asymmetries in these measurements, then the innermost moon Miranda should exhibit similar hemispherical trends due to its high orbital velocity and proximity to Uranus. However, the results presented here, along with previous analyses (Cartwright et al, 2018), indicate that Miranda does not display obvious leading/trailing asymmetries in either its IRAC albedos or H2O ice band strengths. Additionally, although dust collisions could promote burial of existing tiny H2O grains, they could also promote grain fragmentation via impact comminution, thereby generating new tiny grains of H2O ice.…”

Section: Driven By Heliocentric Dust Impacts?supporting

confidence: 55%

“…However, over the center of Ariel's leading hemisphere (LE zone), there is a > 1σ difference between these two datasets, with slightly brighter results for the Program 71 observations. Analysis of short NIR spectra suggest that more H2O ice is exposed over Ariel's northern latitudes compared to its southern latitudes (Cartwright et al, 2018). Consequently, perhaps there is more exposed H2O ice over the northern latitudes of Ariel's leading hemisphere compared to the southern latitudes of its leading side, resulting in greater absorption and lower IRAC albedos.…”

Section: Identification Of Five Distinct Albedo Zones On Arielmentioning

confidence: 99%

“…After comparing the Program 71 and 11112 results, we combined these two datasets into one set of albedo zones (bolded columns in Table 5, Figure 4). Additionally, we compared these IRAC results to the two published SpeX/LXD albedos of this moon (Cartwright et al, 2018), which were collected over Ariel's UF and CT albedo zones. This comparison demonstrates broad agreement between these SpeX/LXD and IRAC albedos (Table 5).…”

Section: Identification Of Five Distinct Albedo Zones On Arielmentioning

confidence: 99%

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Probing the regoliths of the classical Uranian satellites: Are their surfaces mantled by a layer of tiny H2O ice grains?

Cartwright

Emery

Grundy

et al. 2020

Icarus

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We investigate whether the surfaces of the classical moons of Uranus are compositionally stratified, with a thin veneer of mostly tiny H2O ice grains (≤ 2 µm diameters) mantling a lower layer composed of larger grains of H2O ice, dark material, and CO2 ice (~10 -50 µm diameters). Near-infrared observations (~1 -2.5 µm) have determined that the H2O ice-rich surfaces of these moons are overprinted by concentrated deposits of CO2 ice, found almost exclusively on their trailing hemispheres. However, best fit spectral models of longer wavelength datasets (~3 -5 µm) indicate that the spectral signature of CO2 ice is largely absent, and instead, the exposed surfaces of these moons are composed primarily of tiny H2O ice grains. To investigate possible compositional layering of these moons, we have collected new data using the Infrared Array Camera (IRAC) onboard the Spitzer Space Telescope (~3 -5 µm). Spectral modeling of these new data is consistent with prior analyses, suggesting that the exposed surfaces of the Uranian moons are primarily composed of tiny H2O ice grains. Furthermore, analysis of these new data reveal that the trailing hemispheres of these moons are brighter than their leading hemispheres over the 3 to 5 µm wavelength range, except for Miranda, which displays no hemispherical asymmetries in its IRAC albedos. Our analyses also revealed that the surface of Ariel displays five distinct, regionalscale albedo zones, possibly consistent with the spatial distribution of CO2 ice on this moon. We discuss possible processes that could be enhancing the observed leading/trailing albedo asymmetries exhibited by these moons, as well as processes that could be driving the apparent compositional stratification of their near surfaces. 2019a. Exploring the composition of icy bodies at the fringes of the Solar System with next generation space telescopes. arXiv preprint arXiv:1903.07691. Cartwright, R.J., Emery, J.P., Pinilla-Alonso, N., Grundy, W.M., Cruikshank, D.P., 2019b.Probing the regoliths of the classical Uranian satellites using near-infrared telescope observations: Thick deposits of CO2 ice mantled by a thin veneer of tiny H2O ice grains?In AGU Fall Meeting Abstracts.

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Section: Discussionsupporting

confidence: 90%

Section: Best Fit Synthetic Spectrasupporting

confidence: 77%

Section: Driven By Heliocentric Dust Impacts?supporting

confidence: 55%

Section: Identification Of Five Distinct Albedo Zones On Arielmentioning

confidence: 99%

Section: Identification Of Five Distinct Albedo Zones On Arielmentioning

confidence: 99%

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Probing the regoliths of the classical Uranian satellites: Are their surfaces mantled by a layer of tiny H2O ice grains?

Cartwright

Emery

Grundy

et al. 2020

Icarus

Self Cite

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Compositions and Interior Structures of the Large Moons of Uranus and Implications for Future Spacecraft Observations

Castillo‐Rogez

Weiss

Beddingfield

et al. 2022

Preprint

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The five large moons of Uranus are important targets for future spacecraft missions. To motivate and inform the exploration of these moons, we model their internal evolution, present-day physical structures, and geochemical and geophysical signatures that may be measured by spacecraft. We predict that if the moons preserved liquid until present, it is likely in the form of residual oceans less than 30 km thick in Ariel, Umbriel, Titania, and Oberon. The preservation of liquid strongly depends on material properties and, potentially, on dynamical circumstances that are unknown. Miranda is unlikely to preserve liquid until present unless it experienced tidal heating a few tens of million years ago. The triaxial shapes estimated from Voyager 2 data for Miranda and Ariel further support the prospect that these moons are internally differentiated with a rocky core and icy shell. We find that since the thin residual layers may be hypersaline, their induced magnetic fields could be detectable by future spacecraft-based magnetometers. However, if the ocean is maintained primarily by ammonia, and thus well below the water freezing point, then its electrical conductivity may be too small to be detectable by spacecraft. Lastly, our calculated tidal Love number (k 2 ) and dissipation factor (Q) are consistent with the Q/k 2 values previously inferred from dynamical evolution models. In particular, we find that the low Q/k 2 estimated for Titania supports the hypothesis that Titania currently holds an ocean.

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Ice giant system exploration within ESA’s Voyage 2050

et al. 2021

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Of all the myriad environments in our Solar System, the least explored are the distant Ice Giants Uranus and Neptune, and their diverse satellite and ring systems. These ‘intermediate-sized’ worlds are the last remaining class of Solar System planet to be characterised by a dedicated robotic mission, and may shape the paradigm for the most common outcome of planetary formation throughout our galaxy. In response to the 2019 European Space Agency call for scientific themes in the 2030s and 2040s (known as Voyage 2050), we advocated that an international partnership mission to explore an Ice Giant should be a cornerstone of ESA’s science planning in the coming decade, targeting launch opportunities in the early 2030s. This article summarises the inter-disciplinary science opportunities presented in that White Paper [1], and briefly describes developments since 2019.

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Red material on the large moons of Uranus: Dust from the irregular satellites?

Cited by 46 publications

References 79 publications

Probing the regoliths of the classical Uranian satellites: Are their surfaces mantled by a layer of tiny H2O ice grains?

Probing the regoliths of the classical Uranian satellites: Are their surfaces mantled by a layer of tiny H2O ice grains?

Compositions and Interior Structures of the Large Moons of Uranus and Implications for Future Spacecraft Observations

Ice giant system exploration within ESA’s Voyage 2050

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