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Kuiper Prize Lecture: Some Problems and Challenges in the Origin and Evolution of Icy Satellites and Dwarf Planets

Presentation #206.02 in the session Plenary Lectures: Prizes & Planetary Defense: DART & LICIACube (Plenary Lecture)

Published onOct 23, 2023
Kuiper Prize Lecture: Some Problems and Challenges in the Origin and Evolution of Icy Satellites and Dwarf Planets

Forty+ years of planetary exploration have revealed the true glory of the outer Solar System: a vast array of icy worlds, some being planets in all but name. Fundamental understanding of their origin and evolution remains elusive in many ways, however. The recent Decadal Survey outlined the important questions that can be addressed or answered in the next 10 years through a judicious application of robotic and human exploration, astronomical observations, experiments, theory, field work, and other fundamental research. But what about those critical questions that resist answers? And how can we really prove our cherished theories? Asking the right questions is more important than getting the right answers (mostly).

Plate tectonics has ruled the geosciences since the 1960s, but its ultimate proof has come from real-time GPS monitoring. I submit that surface transponders or beacons will be necessary to determine whether something analogous to plate tectonics is occurring presently on Europa. Such surface stations bring with them the ability to determine shell thicknesses from passive “cryo-seismology,” which would be a boon should the sounding radars planned for Europa prove inadequate to the task (unlikely), but would prove their worth for ocean worlds possessing thicker ice shells. In this way we would finally be able to calibrate tidal heating theories. Moreover, precise measurements of orbital secular accelerations would put a pin in estimates of global tidal dissipation within a given icy satellite and its giant planet parent. Barriers to success are primarily technical and fiscal.

Satellite evolution is tied to origins, and thus to the vexing question of when satellites formed, traditionally as a by-product of planet formation but possibly much later from evolving massive rings. Absolute dating of satellite accretion and later geological events demands attention, as does dating if not confirmation of the orbital migration and instability or instabilities among the giant planets. The architecture of the Kuiper belt is the primary evidence for the latter, but its truth will rise or fall as the “limits of completeness” (Kuiper’s term) are pushed ever deeper into transneptunian space. And finally, there is the great coupled question of composition and provenance. JWST is unveiling the true variation in outer Solar System surface compositions, and meteoritics has proposed the great isotopic dichotomy and its possible cause (Jupiter), but full interpretation of the former will require multiple New-Horizons-style exploratory missions and confirmation of the latter in situ and returned sample analyses.

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