Figure 8-10: Temperature Distribution and Snow Line in the Solar Nebula (a) This graph shows how temperatures probably varied across the solar nebula as the planets were forming, and the present-day position of the planets (red arrows). Note the general decline in temperature with increasing distance from the center of the nebula. Between the present-day distances of Mars and Jupiter, the snow line marked where temperatures were low enough for water to condense and form ice; beyond about 16 AU, methane (CH4) could also condense into ice. (b) Terrestrial planets formed inside the snow line, where the low abundance of solid dust grains kept these planets small. The Jovian planets formed beyond the snow line where solid ices of water, methane, and ammonia added their mass to build larger cores, and attract surrounding gas.