2025-11-10 オックスフォード大学
The new study constrained the Enceladus’ global conductive heat flow by studying its seasonal temperature variations at its north pole (yellow). These results, when combined with existing ones of its highly active south polar region (red) provide the first observational constraint of Enceladus’ energy loss budget (<54 GW) – which is consistent with the predicted energy input (50 to 55 GW) from tidal heating. This implies Enceladus’ current activity is sustainable in the long term – an important prerequisite for the evolution of life, which is thought possible to exist in its global sub-surface ocean. Image credit: University of Oxford/NASA/JPL-CalTech/Space Science Institute (PIA19656 and PIA11141)
＜関連情報＞
- https://www.ox.ac.uk/news/2025-11-10-saturn-s-icy-moon-may-host-stable-ocean-fit-life-new-study-finds
- https://www.science.org/doi/full/10.1126/sciadv.adx4338
エンケラドスの北極における内因性熱 Endogenic heat at Enceladus’ north pole
Georgina Miles, Carly J. A. Howett, Francis Nimmo, and Douglas J. Hemingway
Science Advances Published:7 Nov 2025
DOI:https://doi.org/10.1126/sciadv.adx4338
Abstract
The long-term survival of Enceladus’ ocean depends on the balance between heat production and heat loss. To date, the only place where a direct measurement of Enceladus’s heat loss has been made is at the south pole. Here, we show that the north pole also emits heat at a greater rate than can be explained by purely passive models. By comparing winter and summer observations taken with the Cassini Composite InfraRed Spectrometer, we find a winter temperature ~7 kelvin warmer than passive modeling predicts, accounting for uncertainties in emissivity and thermal inertia. An additional endogenic heat flux of 46 ± 4 milliwatts per square meter is required to match the observed radiance. The implied local shell thickness is 20 to 23 kilometers—consistent with the higher end of thickness models based on gravity, topography, and libration measurements. This work provides a previously unidentified constraint for models of tidal heat production, shell thickness, and the long-term evolution of Enceladus’ ocean.
