Snowball planets’ lifeless future

Habitable stage skipped when chilled façades thaw in absence of carbon cycle.

When icy planets without a strong carbon cycle warm up, they might skip straight past a state amenable to life.

Earth escaped its ice-covered ‘snowball’ state as carbon-rich volcanic gas accumulated in and warmed the atmosphere, making the planet habitable. Researchers have previously proposed that planets and moons without such gaseous carbon conditions might also reach similar life-hosting states as their stars become brighter and melt the ice away.

Jun Yang and Yongyun Hu at Peking University in Beijing and their team modelled such climate evolution on snowball planets that have neither an active carbon cycle nor enough greenhouse gases to trap water vapour in their atmospheres. They found that the amount of stellar energy needed to melt these icy planets is so great that the worlds would shoot straight past a life-hosting sweet spot, and all their water would boil away.