Fig. 1: Derived depths of penetration of solar radiation into the Enceladus surface for various regolith grain sizes.
From: Low effective ultraviolet exposure ages for organics at the surface of Enceladus
Larger grain sizes result in greater penetration depths; the Enceladus surface is likely to be dominated by grains <1-5 micrometers in diameter2. Also shown are the estimated penetration depths into pure ice (red & black lines/asterisks), using two different sets of optical constants. Pure ice penetration depths are much deeper than for Enceladus because of the granular nature of the Enceladus regolith (compared with the layers of ice used in the lab to derive the optical constants for pure water ice) in addition to the non-ice component of the Enceladus regolith. We note that measurements by Picard et al. (2016)60 resulted in values intermediate between the datasets represented by the black and red lines.
