Six or seven billion years from now the sun will begin to die, but it will not die alone. In its death throes it will swell into a red giant star, engulfing and incinerating Mercury, Venus, and Earth. Although life on Earth—if indeed any still exists—will surely end, a new theory suggests that the sun’s final agony may make possible the evolution of life on another world in the solar system—Saturn’s moon Titan.
Unlike any other moon in the solar system, Titan has a dense atmosphere composed mostly of nitrogen, as is Earth’s, and about 2 to 10 percent methane. Ultraviolet light from the sun breaks the methane apart, creating a thick, smoggy haze of organic compounds that hides Titan’s surface. And on that surface, some astronomers believe, lie seas of methane. Titan is also an extremely cold place. Besides being 900 million miles from the sun, the moon has ...
