New research suggests that signs of alien life could be trapped beneath layers of high-pressure ice on distant exoplanets. Scientists have modelled rocky worlds with very deep oceans and found that liquid water could exist under thick ice sheets, potentially harbouring life.
The study, led by Dr Lena Noack from the Royal Observatory of Belgium, examined planets with Earth-like mass but oceans up to 15 times deeper than our own. On such a planet, a layer of high-pressure ice can form at depths of around 100 miles (170km). However, if enough heat flows from the planet's interior, water beneath the ice can remain liquid, creating a possible habitat for life.
Two exoplanets that could fit this description are Kepler-62e and Kepler-62f, discovered by NASA's Kepler mission in 2013. Kepler-62f is about 1.4 times the size of Earth and lies 1,200 light-years away in the constellation Lyra. Kepler-62e is estimated to be 1.6 times larger. Their predicted densities suggest they could have a high water content.
The model applies to planets up to ten times Earth's mass; larger worlds would have too much gravitational pressure for liquid water to form. The researchers also note that Jupiter's moon Ganymede, which has a high proportion of water, could similarly have a thick ice layer covering liquid water, depending on internal heat.
