Heat from radioactivity, not starlight, could warm planets enough to allow liquid water to exist on their surfaces. By Katherine KorneiNot too close, but not too far.
That’s long been the rule describing how distant a planet should be from its star in order to sustain life. But a new study challenges that adage: A planet can maintain water and other liquids on its surface if it’s heated, not by starlight, but by radioactive decay, researchers calculate.
That opens up the possibility for many planets-even free-floating worlds untethered to stars—to host life, they speculate.Radioactive isotopes such as uranium-238, thorium-232, and potassium-40 pepper Earth’s crust and mantle.