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Geophysical evidence that Saturn's Moon Phoebe originated from a C-type asteroid reservoir

Abstract : Saturn's Moon Phoebe has been suggested to originate from the Kuiper Belt. However, its density is twice that of Kuiper Belt objects (KBOs) in the same size class, which challenges that relationship. Since the internal evolution of mid-sized planetesimals (100-300 km in diameter) is primarily driven by the amount of accreted short-lived radioisotopes, it is possible to constrain the relative times of formation of these bodies based on their bulk porosity content, hence their densities. From modelling the thermal evolution of KBOs, we infer a difference in formation timing between these bodies and Phoebe. This confirms prior suggestions for a delayed accretion timeframe with increasing distance from the Sun. This geophysical finding combined with spectral observations suggests Phoebe formed in the same region as C-type asteroids and support recent dynamical models for a C-type body reservoir between the orbits of the giant planets. On the other hand, the similarly low densities of mid-sized D-type asteroids, Trojan asteroids, and KBOs add to the growing evidence that these objects shared a common reservoir near or beyond the orbit of Neptune and were heat starved overall.
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Contributor : Nathalie Pothier Connect in order to contact the contributor
Submitted on : Thursday, May 12, 2022 - 5:23:34 PM
Last modification on : Saturday, May 14, 2022 - 3:03:54 AM


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Julie Castillo-Rogez, Pierre Vernazza, Kevin Walsh. Geophysical evidence that Saturn's Moon Phoebe originated from a C-type asteroid reservoir. Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP): Policy P - Oxford Open Option A, 2019, 486, pp.538-543. ⟨10.1093/mnras/stz786⟩. ⟨insu-03666743⟩



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