The End of Life on Earth

The Earth can’t live forever. In a mere 5.4 billion years, the Sun will exhaust the hydrogen in its core and begin fusing helium. Once the source of our planet’s habitability, the Sun will engulf Mercury, Venus, and potentially Earth. Even if all life on Earth ceases to exist, this could be the beginning of a new evolution of life in the outer Solar System. Although Jupiter and Saturn are gas giants without solid surfaces, their moons offer small terrestrial worlds that could harbor the development of life. 

Jovian Moons Today

Today, some moons of Jovian planets already contain components to support life. Titan, the largest moon of Saturn, has a thick and active atmosphere with large bodies of liquid methane and ethane. Even if there is no liquid water, the existence of methane based organisms has been modeled by a team of Cornell University researchers. Orbiting Jupiter, Europa has a thick icy crust that covers an ocean with more water than Earth. Due to tidal forces, the underground ocean doesn’t freeze over, creating the potential for life in the dark depths. Similarly, Enceladus has liquid water, as well as organic carbon, nitrogen, and an energy source.

"There is no other environment in the Solar System where we can make all those claims."

-Chris McKay, astrobiologist, NASA's Ames Research Center, speaking of Enceladus




Even if the moons are still too inhospitable for the development of life, that doesn’t necessarily seal their future. Under a red giant Sun, these moons would shed their icy layers, revealing the subsurface oceans. These Jovian moons could become the second phase of life in the Solar System.

Detecting Exomoons

But why stop there? If Jovian moons could be habitable in billions of years in our Solar System, what does that say about moons orbiting exoplanets hundreds of light years away? Beyond the search for habitable exoplanets, the next logical step is to search for exomoons. Ideally, these worlds would orbit super-Earths or gas giants within the habitable region of the host star. Current observational technology cannot detect exomoons. Although there exist many conceptual methods for finding them (most notably through transit timing), it may be a few years until observational precision pushes the barrier from exoplanets to exomoons.