abundance ratio in chemical equilibrium of a gas of the solar-system elemental
abundance. The dashed lines indicate contours of constant
;
along the solid line labeled CO-CH
. The quenching temperature for CO to CH
conversion is shown by the curve labeled by
. Here the quenching temperature
is defined as the temperature at which the time required to achieve chemical
equilibrium,
, becomes equal to the nebular dynamical time scale, for which Fegley and
Prinn (1989) take
s. The dash-dotted curves indicate the temperature-pressure profiles of
the solar nebula and Jovian subnebula that they supposed. [Taken from Fegley
and Prinn (1989).]
Fig. 6: Sublimation temperatures
of the candidate parent molecules of the cometary ice as a function of
the gas density of the solar nebula.
is the temperature of the nebular gas at which each of the molecular species
sublimes, and
is the corresponding grain temperature. The emissivity of
(Greenberg, 1978) and the background radiation temperature of K (Kusaka
et al., 1970) are adopted. Two temperature distributions of the
solar nebula are shown with the formation regions of the planets indicated
by M, V, E, : (A) the radiative equilibrium distribution (Hayashi, 1981),
and (B) the adiabatic distribution (Cameron, 1978).
Fig. 7: Schematic illustration of transition of amorphous ice
to crystalline ice.
Fig. 8: Temperature in the interior of a cometary nucleus as
a function of time for the nucleus radius
km, the silicate mass fraction x=0.5, and the reduction factor
.
Fig. 9: The same as in Fig. 8 except for
.
Fig. 10: Degree of crystallization,
, at the center of the nucleus after
yr as a function of the reduction factor for
of
km and x=0.5.
Fig. 11: Schematic behavior of
as a function of temperature.