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Scientific rationale for Saturn's in situ exploration

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journal contribution
posted on 18.01.2017, 16:48 by O. Mousis, L. N. Fletcher, J. P. Lebreton, P. Wurz, T. Cavalié, A. Coustenis, R. Courtin, D. Gautier, R. Helled, P. G. J. Irwin, A. D. Morse, N. Nettelmann, B. Marty, P. Rousselot, O. Venot, D. H. Atkinson, J. H. Waite, K. R. Reh, A. A. Simon, S. Atreya, N. André, M. Blanc, I. A. Daglis, G. Fischer, W. D. Geppertt, T. Guillot, M. M. Hedman, R. Hueso, E. Lellouch, J. I. Lunine, C. D. Murray, J. O'Donoghue, M. Rengel, A. Sánchez-Lavega, F. X. Schmider, A. Spiga, T. Spilker, J-M. Petit, M. S. Tiscareno, M. Ali-Dib, K. Altwegg, S. J. Bolton, A. Bouquet, C. Briois, T. Fouchet, S. Guerlet, T. Kostiuk, D. Lebleu, R. Moreno, G. S. Orton, J. Poncy
Remote sensing observations meet some limitations when used to study the bulk atmospheric composition of the giant planets of our solar system. A remarkable example of the superiority of in situ probe measurements is illustrated by the exploration of Jupiter, where key measurements such as the determination of the noble gases׳ abundances and the precise measurement of the helium mixing ratio have only been made available through in situ measurements by the Galileo probe. This paper describes the main scientific goals to be addressed by the future in situ exploration of Saturn placing the Galileo probe exploration of Jupiter in a broader context and before the future probe exploration of the more remote ice giants. In situ exploration of Saturn׳s atmosphere addresses two broad themes that are discussed throughout this paper: first, the formation history of our solar system and second, the processes at play in planetary atmospheres. In this context, we detail the reasons why measurements of Saturn׳s bulk elemental and isotopic composition would place important constraints on the volatile reservoirs in the protosolar nebula. We also show that the in situ measurement of CO (or any other disequilibrium species that is depleted by reaction with water) in Saturn׳s upper troposphere may help constraining its bulk O/H ratio. We compare predictions of Jupiter and Saturn׳s bulk compositions from different formation scenarios, and highlight the key measurements required to distinguish competing theories to shed light on giant planet formation as a common process in planetary systems with potential applications to most extrasolar systems. In situ measurements of Saturn׳s stratospheric and tropospheric dynamics, chemistry and cloud-forming processes will provide access to phenomena unreachable to remote sensing studies. Different mission architectures are envisaged, which would benefit from strong international collaborations, all based on an entry probe that would descend through Saturn׳s stratosphere and troposphere under parachute down to a minimum of 10 bar of atmospheric pressure. We finally discuss the science payload required on a Saturn probe to match the measurement requirements.

Funding

O.M. acknowledges support from CNES. L.N.F. was supported by a Royal Society Research Fellowship at the University of Oxford. P.W. acknowledges support from the Swiss National Science Foundation. O.V. acknowledges support from the KU Leuven IDO project IDO/10/2013 and from the FWO Postdoctoral Fellowship program. A.S.L. and R.H. were supported by the Spanish MICIIN project AYA2012-36666 with FEDER support, PRICIT-S2009/ESP-1496, Grupos Gobierno Vasco IT765-13 and UPV/EHU UFI11/55, G.F. acknowledges support from the Austrian Science Fund FWF via project P24325-N16.

History

Citation

Planetary and Space Science, 2014, 104, pp. 29-47 (19)

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy

Version

AM (Accepted Manuscript)

Published in

Planetary and Space Science

Publisher

Elsevier

issn

0032-0633

Acceptance date

25/09/2014

Available date

18/01/2017

Publisher version

http://www.sciencedirect.com/science/article/pii/S0032063314002955

Language

en