Researchers have identified more than 121 giant planets that potentially host moons capable of supporting life. These giant planets have orbits within the habitable zones of their stars, meaning it's neither too hot nor too cold for liquid water -- and potentially life -- to exist.

At more than three times the radii of the Earth, these gaseous planets are less common than terrestrial (rocky) planets, but each is expected to host several large moons. "There are currently 175 known moons orbiting the eight planets in our solar system. While most of these moons orbit Saturn and Jupiter, which are outside the Sun's habitable zone, that may not be the case in other solar systems," said Stephen Kane, Associate Professor at the University of California, Riverside (UCR), in the US.