Scientific rationale for Uranus and Neptune in situ explorations

O. Mousis (1) , D. H. Atkinson (2) , T. Cavalié (3) , L. N. Fletcher (4) , M. J. Amato (5) , S. Aslam (5) , F. Ferri (6) , Jean-Baptiste Renard (7) , T. Spilker (8) , E. Venkatapathy (9) , P. Wurz (10, 11) , K. Aplin (12) , A. Coustenis (3) , M. Deleuil (1) , M. Dobrijevic (13) , T. Fouchet (3) , T. Guillot (14) , P. Hartogh (15) , T. Hewagama (16, 5) , M. D. Hofstadter (8) , V. Hue (13) , R. Hueso (17) , Jean-Pierre Lebreton (7) , E. Lellouch (3) , J. Moses (18) , G. S. Orton (8) , J. C. Pearl (5) , A. Sanchez-Lavega (4) , A. Simon (5) , O. Venot (19) , J. H. Waite (20) , R. K. Achterberg (21, 5) , S. Atreya (22) , F. Billebaud (13) , M. Blanc (23) , Fabien Borget (24) , B. Brugger (25) , S. Charnoz (26, 27) , T. Chiavassa (24) , V. Cottini (21, 5) , L. d'Hendecourt (28) , G. Danger (24) , T. Encrenaz (3) , N. J. P. Gorius (5) , L. Jorda (1) , B. Marty (29) , R. Moreno (3) , A. Morse (30) , C. Nixon (5) , K. Reh (8) , T. Ronnet (1) , F.-X. Schmider (14) , S. Sheridan (31) , C. Sotin (8) , P. Vernazza (1) , G. L. Villanueva (5)

1 LAM - Laboratoire d'Astrophysique de Marseille
2 University of Idaho [Moscow, USA]
3 LESIA (UMR_8109) - Laboratoire d'études spatiales et d'instrumentation en astrophysique
4 University of Leicester
5 GSFC - NASA Goddard Space Flight Center
6 CISAS - Centro di Ateneo di Studi e Attività Spaziali “Giuseppe Colombo”
7 LPC2E - Laboratoire de Physique et Chimie de l'Environnement et de l'Espace
8 JPL - Jet Propulsion Laboratory
9 ARC - NASA Ames Research Center
10 Physikalisches Institut [Bern]
11 CSH - Center for Space and Habitability
12 AOPP - Department of Atmospheric, Oceanic and Planetary Physics [Oxford]
13 ASP 2018
14 LAGRANGE - Joseph Louis LAGRANGE
15 MPS - Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research
16 University of Maryland [College Park]
17 Departamento de Fisica Aplicada [Bilbao]
18 SSI - Space Science Institute [Boulder]
19 LISA (UMR_7583) - Laboratoire Interuniversitaire des Systèmes Atmosphériques
20 Space Science and Engineering Division [San Antonio]
21 Department of Astronomy [College Park]
22 University of Michigan [Ann Arbor]
23 IRAP - Institut de recherche en astrophysique et planétologie
24 PIIM - Physique des interactions ioniques et moléculaires
25 UTINAM - Univers, Transport, Interfaces, Nanostructures, Atmosphère et environnement, Molécules (UMR 6213)
26 AIM (UMR7158 / UMR_E_9005 / UM_112) - Astrophysique Interprétation Modélisation
27 IPGP - Institut de Physique du Globe de Paris
28 IAS - Institut d'astrophysique spatiale
29 CRPG - Centre de Recherches Pétrographiques et Géochimiques
30 School of Physical Sciences [Milton Keynes]
31 OU - The Open University [Milton Keynes]

The ice giants Uranus and Neptune are the least understood class of planets in our solar system but the most frequently observed type of exoplanets. Presumed to have a small rocky core, a deep interior comprising ~70% heavy elements surrounded by a more dilute outer envelope of H2 and He, Uranus and Neptune are fundamentally different from the better-explored gas giants Jupiter and Saturn. Because of the lack of dedicated exploration missions, our knowledge of the composition and atmospheric processes of these distant worlds is primarily derived from remote sensing from Earth-based observatories and space telescopes. As a result, Uranus's and Neptune's physical and atmospheric properties remain poorly constrained and their roles in the evolution of the Solar System not well understood. Exploration of an ice giant system is therefore a high-priority science objective as these systems (including the magnetosphere, satellites, rings, atmosphere, and interior) challenge our understanding of planetary formation and evolution. Here we describe the main scientific goals to be addressed by a future in situ exploration of an ice giant. An atmospheric entry probe targeting the 10-bar level, about 5 scale heights beneath the tropopause, would yield insight into two broad themes: i) the formation history of the ice giants and, in a broader extent, that of the Solar System, and ii) the processes at play in planetary atmospheres. The probe would descend under parachute to measure composition, structure, and dynamics, with data returned to Earth using a Carrier Relay Spacecraft as a relay station. In addition, possible mission concepts and partnerships are presented, and a strawman ice-giant probe payload is described. An ice-giant atmospheric probe could represent a significant ESA contribution to a future NASA ice-giant flagship mission.

Mots clés: atmosphere; Neptune; Uranus; Entry probe; Astrophysics - Earth and Planetary Astrophysics; evolution; formation

Domaines: Planétologie et astrophysique de la terre [astro-ph.EP]

O. Mousis, D. H. Atkinson, T. Cavalié, L. N. Fletcher, M. J. Amato, et al.. Scientific rationale for Uranus and Neptune in situ explorations. Planetary and Space Science, 2018, 155, pp.12-40. ⟨10.1016/j.pss.2017.10.005⟩. ⟨hal-01582556⟩