Why doesn't the ice on comets or on the moon Enceladus sublime? Enceladus doesn't have an atmosphere, so what is it that prevents Enceladus' water ice surface from becoming a gas? Did I miss something?

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    $\begingroup$ Ice sublimes, it does not boil. It is very slow process at low T, slowing down like exponentially with T. Nature 2005: Atmosphere found on Enceladus $\endgroup$
    – Poutnik
    Commented Aug 13, 2022 at 11:08
  • $\begingroup$ @Poutnik Thank you. There's still the question why tiny comets don't sublime around their aphelions though. How long would it take for a 1 mile (1.6 km) diameter comet to sublime (disregarding their evaporation in proximity of the Sun)? $\endgroup$ Commented Aug 13, 2022 at 11:59
  • $\begingroup$ See also engineeringtoolbox.com/ice-thermal-properties-d_576.html for table and chart of progressive decrease of vapor pressure. Enceladus noon t (of static surface) is reportedly near -190 °C. $\endgroup$
    – Poutnik
    Commented Aug 13, 2022 at 12:13
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    $\begingroup$ And once some comes off, the partial pressure at the surface is no longer zero. $\endgroup$
    – Jon Custer
    Commented Aug 13, 2022 at 14:54
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    $\begingroup$ For a comet at aphelion? Much longer than the age of the universe. $\endgroup$
    – Mithoron
    Commented Aug 13, 2022 at 16:49


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