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29P/Schwassmann-Wachmann: A Rosetta Stone for Amorphous Water Ice and CO₂ -> CO Conversion in Centaurs and Comets?

Presentation #408.06 in the session Comets: Nucleus (Oral Presentation)

Published onOct 23, 2023
29P/Schwassmann-Wachmann: A Rosetta Stone for Amorphous Water Ice and CO₂ -> CO Conversion in Centaurs and Comets?

Centaur 29P/Schwassmann-Wachmann 1 is a highly active object orbiting in the transitional “Gateway” region between the Centaur and Jupiter Family Comet regions. SW1 is unique among the Centaurs, in that it experiences quasi-regular major outbursts and produces CO emission continuously; however, the source of the CO is unclear. We argue that due to its very large size (~32 km radius, Schambeau et al. 2015, 2020), Centaur SW1 is likely still responding, via amorphous water ice (AWI) conversion to crystalline water ice (CWI), to the “sudden” change in its external thermal environment produced by its dynamical migration from the Kuiper belt to the Gateway Region at the inner edge of the Centaur region at 6 au. It is this conversion process that we believe is the source of the abundant CO and dust released from SW1’s nucleus during its quiescent and outburst phases. If correct, these arguments have a number of important, testable predictions (Lisse et al. 2022), including: the quick release on Myr timescales of CO from AWI conversion for any few km-scale scattered disk TNO transiting into the inner system; that to date SW1 has only converted between 50 to 65% of its nuclear AWI to CWI; that volume changes upon AWI conversion could have caused subsidence and cave-ins, but not significant mass wasting on SW1; that when SW1 transits into the inner system within the next ~1 Myr, it will be a very different kind of SP comet; and that SW1’s coma should contain abundant amounts of CWI + CO2-rich “dust” particles that only slowly release their contents at large distances as they stream away from the nucleus.

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