Mr. McMahon continued: "The deepest known life on Earth is 5.3km below the
surface, but there may well be life even 10km deep in places on Earth that
haven't yet been drilled.
"Using our computer model we discovered that the habitable zone for an
Earth-like planet orbiting a sun-like star is about three times bigger if we
include the top five kilometers below the planet surface.
"The model shows that liquid water, and as such life, could survive 5km below
the Earth's surface even if the Earth was three times further away from the sun
than it is just now.
"If we go deeper, and consider the top 10km below the Earth's surface, then
the habitable zone for an Earth-like planet is 14 times wider."
He added: "The results suggest life may occur much more commonly deep within
planets and moons than on their surfaces.
"This means it might be worth looking for signs of life outside conventional
habitable zones."
