Analytic solution of pressure distribution P(r) of water vapor in cometary nucleus. Panel (a) shows P(r) near the contact boundary between the primitive region and the dust mantle in the case with R = 1 km and Δ = 1 cm. Panels (b) and (c) show the dependence on Δ. Panel (b) is a magnified view of P(r) in the primitive region, and panel (c) is in the dust mantle. The horizontal axis indicates the distance from the contact boundary, where negative values indicate the primitive region side and positive values indicate the dust mantle side. Note that the horizontal axis in panel (c) is normalized by Δ. The region corresponding to the dust mantle is filled in gray. The pressure in the vertical axis is normalized by the equilibrium vapor pressure P_e.