Surface compositions across Pluto and Charon

Grundy, W. M.; Binzel, Richard P.; Buratti, B. J.; Cook, J. C.; Cruikshank, D. P.; Ore, C. M. Dalle; Earle, A. M.; Ennico, K.; Howett, C. J. A.; Lunsford, Allen; Olkin, C. B.; Parker, A. H.; Sylvain, Philippe; Protopapa, S.; Quirico, E.; Reuter, Dennis C.; Schmitt, Bernard; Singer, K. N.; Verbiscer, A.; Beyer, R. A.; Buie, M. W.; Cheng, A. F.; Jennings, Donald E.; Linscott, I. R.; Parker, J. Wm.; Schenk, P.; Spencer, J. R.; Stansberry, J.; Stern, S. A.; Throop, H. B.; Tsang, C. C. C.; Weaver, Harold A.; Weigle, Gerald; Young, L. A.

doi:10.1126/science.aad9189

Cited by 268 publications

(251 citation statements)

References 54 publications

(89 reference statements)

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“…Hence water-ice blocks can float in solid N 2 or CO, but not in solid CH 4 . Water ice has been identified in the rugged mountains that surround SP 3 , and blocks and other debris shed from the mountains at SP's periphery appear to be floating 2 ; moreover, glacial inflow appears to carry along water-ice blocks, and these blocks almost exclusively congregate at the margins of the cells/polygons, consistent with being dragged to the downwelling limbs of convective cells (Fig. 2a).…”

mentioning

confidence: 78%

Convection in a volatile nitrogen-ice-rich layer drives Pluto’s geological vigour

McKinnon

Nimmo

Wong

et al. 2016

Nature

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The vast, deep, volatile-ice-filled basin informally named Sputnik Planum is central to Pluto's geological activity 1,2 . Composed of molecular nitrogen, methane, and carbon monoxide ices 3 , but dominated by N2-ice, this ice layer is organized into cells or polygons, typically ~10-40 km across, that resemble the surface manifestation of solid state convection 1,2 . Here we report, based on available rheological measurements 4 , that solid layers of N2 ice ≳1 km thick should convect for estimated present-day heat flow conditions on Pluto. More importantly, we show numerically

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mentioning

confidence: 78%

Convection in a volatile nitrogen-ice-rich layer drives Pluto’s geological vigour

McKinnon

Nimmo

Wong

et al. 2016

Nature

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110

120

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“…The term tholins was introduced by Sagan and Khare () to name the “brown, sometimes sticky, residue” they produced in laboratory at Cornell University by irradiating with various sources of energy a mixture of the cosmically abundant gases CH 4 , C 2 H 6 , NH 3 , H 2 O, HCHO, and H 2 S. The definition was later expanded to include many other components produced from different mixtures and even by irradiation of ices. It now seems that tholin‐like materials are present in many bodies in the solar system: on Pluto (Grundy et al, ), Charon (Grundy et al, ), comets (McDonald et al, ; Stern et al, ), Triton (McDonald et al, ) and, of course, Titan (Sagan et al, ).…”

Section: Methodsmentioning

confidence: 99%

Electrical Properties of Tholins and Derived Constraints on the Huygens Landing Site Composition at the Surface of Titan

et al. 2018

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In 2005, the complex permittivity of the surface of Saturn's moon Titan was measured by the PWA‐MIP/HASI (Permittivity Wave Altimetry‐Mutual Impedance Probe/Huygens Atmospheric Structure Instrument) experiment on board the Huygens probe. The analysis of these measurements was recently refined but could not be interpreted in terms of composition due to the lack of knowledge on the low‐frequency/low‐temperature electrical properties of Titan's organic material, a likely key ingredient of the surface composition. In order to fill that gap, we developed a dedicated measurement bench and investigated the complex permittivity of analogs of Titan's organic aerosols called “tholins.” These laboratory measurements, together with those performed in the microwave domain, are then used to derive constraints on the composition of Titan's first meter below the surface based on both the PWA‐MIP/HASI and the Cassini Radar observations. Assuming a ternary mixture of water ice, tholin‐like dust and pores (filled or not with liquid methane), we find that at least 10% of water ice and 15% of porosity are required to explain observations. On the other hand, there should be at most 50–60% of organic dust. PWA‐MIP/HASI measurements also suggest the presence of a thin conductive superficial layer at the Huygens landing site. Using accurate numerical simulations, we put constraints on the electrical conductivity of this layer as a function of its thickness (e.g., in the range 7–40 nS/m for a 7‐mm thick layer). Potential candidates for the composition of this layer are discussed.

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“…Among the most striking observations of Pluto, made by the cameras aboard New Horizons during the July 2015 flyby, is a planetary‐scale multikilometer‐thick equatorial

{normalN}_{2}

‐rich ice sheet (mixed with small amounts of CO and

{CH}_{4}

), covering the floor of the Sputnik Planitia basin that extends between latitudes 25°S and 50°N at a level 3 km below the surrounding terrains (Grundy et al, ; Stern et al, ; Schenk et al, ). Highlands to the east of this structure are also covered by

{normalN}_{2}

‐rich ices, which merge with the ices of Sputnik Planitia through several valley glaciers (Howard et al, ; Protopapa et al, ; Schmitt et al, ).…”

Section: Introductionmentioning

confidence: 99%

Pluto's Beating Heart Regulates the Atmospheric Circulation: Results From High‐Resolution and Multiyear Numerical Climate Simulations

et al. 2020

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Pluto's atmosphere is mainly nitrogen and is in solid‐gas equilibrium with the surface nitrogen ice. As a result, the global nitrogen ice distribution and the induced nitrogen condensation‐sublimation flows strongly control the atmospheric circulation. It is therefore essential for Global Climate Models to accurately account for the global nitrogen ice distribution in order to realistically simulate Pluto's atmosphere. Here we present a set of new numerical simulations of Pluto's atmosphere in 2015 performed with a Global Climate Model using a 50‐km horizontal resolution (3.75° × 2.5°) and taking into account the latest topography and ice distribution data, as observed by the New Horizons spacecraft. In order to analyze the seasonal evolution of Pluto's atmosphere dynamics, we also performed simulations at coarser resolution (11.25° × 7.5°) but covering three Pluto years. The model predicts a near‐surface western boundary current inside the Sputnik Planitia basin in 2015, which is consistent with the dark wind streaks observed in this region. We find that this atmospheric current could explain the differences in ice composition and color observed in the northwestern regions of Sputnik Planitia, by significantly impacting the nitrogen ice sublimation rate in these regions through processes possibly involving conductive heat flux from the atmosphere, transport of dark materials by the winds, and surface albedo positive feedbacks. In addition, we find that this current controls Pluto's general atmospheric circulation, which is dominated by a retrorotation, independently of the nitrogen ice distribution outside Sputnik Planitia. This exotic circulation regime could explain many of the geological features and longitudinal asymmetries in ice distribution observed all over Pluto's surface.

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Surface compositions across Pluto and Charon

Cited by 268 publications

References 54 publications

Convection in a volatile nitrogen-ice-rich layer drives Pluto’s geological vigour

Convection in a volatile nitrogen-ice-rich layer drives Pluto’s geological vigour

Electrical Properties of Tholins and Derived Constraints on the Huygens Landing Site Composition at the Surface of Titan

Pluto's Beating Heart Regulates the Atmospheric Circulation: Results From High‐Resolution and Multiyear Numerical Climate Simulations

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