Cometary plasma science: Open science questions for future space missions

Comets hold the key to the understanding of our Solar System, its formation and its evolution, and to the fundamental plasma processes at work both in it and beyond it. A comet nucleus emits gas as it is heated by the sunlight. The gas forms the coma, where it is ionised, becomes a plasma, and eventually interacts with the solar wind. Besides these neutral and ionised gases, the coma also contains dust grains, released from the comet nucleus. As a cometary atmosphere develops when the comet travels through the Solar System, large-scale structures, such as the plasma boundaries, develop and disappear, while at planets such large-scale structures are only accessible in their fully grown, quasi-steady state. In situ measurements at comets enable us to learn both how such large-scale structures are formed or reformed and how small-scale processes in the plasma affect the formation and properties of these large scale structures. Furthermore, a comet goes through a wide range of parameter regimes during its life cycle, where either collisional processes, involving neutrals and charged particles, or collisionless processes are at play, and might even compete in complicated transitional regimes. Thus a comet presents a unique opportunity to study this parameter space, from an asteroid-like to a Mars- and Venus-like interaction. The Rosetta mission and previous fast flybys of comets have together made many new discoveries, but the most important breakthroughs in the understanding of cometary plasmas are yet to come. The Comet Interceptor mission will provide a sample of multi-point measurements at a comet, setting the stage for a multi-spacecraft mission to accompany a comet on its journey through the Solar System. This White Paper, submitted in response to the European Space Agency’s Voyage 2050 call, reviews the present-day knowledge of cometary plasmas, discusses the many questions that remain unanswered, and outlines a multi-spacecraft European Space Agency mission to accompany a comet that will answer these questionsby combining both multi-spacecraft observations and a rendezvous mission, and at the same time advance our understanding of fundamental plasma physics and its role in planetary systems.

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Funding Information: C. G. is supported by an ESA Research Fellowship. H. G. acknowledges support by the Swedish National Space Agency grant 108/18. B. S.-C. acknowledges support through UK-STFC grant ST/S000429/1. French co-authors acknowledge the support of CNES for the Rosetta and Comet Interceptor missions. I. M. acknowledges support through grants of Research Council of Norway (262941 and 275503). Publisher Copyright: © 2021, The Author(s), under exclusive licence to Springer Nature B.V.

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Comet, Plasma, Rosetta

DOI

10.1007/s10686-021-09783-z

Citation

Goetz , C , Gunell , H , Volwerk , M , Beth , A , Eriksson , A , Galand , M , Henri , P , Nilsson , H , Wedlund , C S , Alho , M , Andersson , L , Andre , N , De Keyser , J , Deca , J , Ge , Y , Glassmeier , K H , Hajra , R , Karlsson , T , Kasahara , S , Kolmasova , I , LLera , K , Madanian , H , Mann , I , Mazelle , C , Odelstad , E , Plaschke , F , Rubin , M , Sanchez-Cano , B , Snodgrass , C & Vigren , E 2021 , ' Cometary plasma science: Open science questions for future space missions ' , Experimental Astronomy . https://doi.org/10.1007/s10686-021-09783-z

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https://urn.fi/URN:NBN:fi:aalto-202109089091

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[article-cris] Sähkötekniikan korkeakoulu / ELEC

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Cometary plasma science: Open science questions for future space missions

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