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.
Just as our moon is tidally locked to the Earth, only showing us one hemisphere, the same is true of these exoplanets facing red dwarves. 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.
It would all depend on the parameters of the ice flow and melt, and whether that band of water left in the middle could be maintained. ‘No matter how efficient you are at trapping water on night side, there always has to be some water on the dayside,’ Dr Menou said.
Accordingly, small pockets of habitability might remain in these water-trapped worlds. Red dwarves make up approximately three quarters of the stars in the solar system, making the existence of some of these planets orbiting them much more likely.
