In a protoplanetary disk , the inner edge of the region where the temperature falls below the condensation temperature of water is referred to as the ’ snow line ’ .
Outside the snow line , water ice increases the surface density of solids by a factor of 4 .
The mass of the fastest growing planetesimal ( the ’ isolation mass ’ ) scales as the surface density to the 3/2 power .
It is thought that ice-enhanced surface densities are required to make the cores of the gas giants ( Jupiter and Saturn ) before the disk gas dissipates .
Observations of the Solar System ’ s asteroid belt suggest that the snow line occurred near 2.7 AU .
In this paper we revisit the theoretical determination of the snow line .
In a minimum-mass disk characterized by conventional opacities and a mass accretion rate of 10 ^ { -8 } M _ { \odot } / { yr } , the snow line lies at 1.6–1.8 AU , just past the orbit of Mars .
The minimum-mass disk , with a mass of 0.02 M _ { \odot } , has a life time of 2 million years with the assumed accretion rate .
Moving the snow line past 2.7 AU requires that we increase the disk opacity , accretion rate , and/or disk mass by factors ranging up to an order of magnitude above our assumed baseline values .