From the Daily Mail:
Earth-like planets may be able to support life in a small area of their surface even if most of their water is permanently frozen, a new study has found.
Planets that orbit red dwarf stars, known as exoplanets, can become 'tidally locked' so that their water is frozen on their permanently cold night-time sides but they could still sustain life, astronomer Kristen Menou at Columbia University has explained.
... As a result, the planets have a permanent day side and permanent night side.
This means that the water is trapped unable to reach the temperate side of the planet, creating huge glaciers on the cold, dark side.
If the water moved around to the hot, daytime side of the planets, however, the water would simply evaporate.
On the night-side there would still be ice covering the surface, creating an unusual 'eyeball earth' effect.
This leaves only a thin band of water around the planet where the temperature was just right for it to remain liquid, and this is where organisms could grow.
This band is hoped to exist on planets very close to red dwarfs, which are not as hot as our sun.
The water-trapping principle is a major clue in trying to access the potential habitability of red dwarf orbiting planets.