In unknown places in the galaxy, life could be hiding. The satellites of some exoplanets could be as hot and humid as Earth
Could there be life besides Earth? The question has been unanswered for millennia, yet exoplanet research may soon lead to a positive statement. It all depends on water, and studies are focusing within the circumstellar habitable zone (CHZ) that surrounds stars. For our solar system, this area would be roughly between the orbits of Venus and Mars. Most exoplanets that meet these criteria are super Earths orbiting small red dwarf stars. These worlds are too hot to be habitable, but their moons may have similar temperature and humidity to the Earth's globe.
Studies on exoplanets with water
Recent research has identified how large gaseous planets don't even necessarily have to orbit near their star to have water-filled moons. For example, Ganymede, one of Jupiter's satellites, has an ocean beneath its icy surface, and Europa also has more water than Earth. What's interesting is that the presence of liquid water on these moons is not due to the Sun's heat, but to thermal heating caused by their planet's gravitational tug.
In a recent paper published in the International Journal of Astrobiology, scientists wondered how potentially habitable exolunas could form and whether they could maintain liquid water long enough to allow the evolution of primordial life. If light and heat from the star are needed for moons within a star system, for those on exoplanets, a primary influence would be cosmic rays. This, combined with tidal heating, could lead to the evolution of the lunar atmosphere over time.
The team of researchers modeled an Earth-mass moon orbiting a Jupiter-mass exoplanet. They found that, with some assumptions about chemical composition and orbital stability, an exoluna could maintain liquid water on its surface, albeit to a lesser degree than Earth. In any case it could be enough to allow life to evolve.
While studies continue on the possibility of making habitable new worlds in space in addition to Earth, Jeff Bezos is preparing to leave on the New Shepard in the mission that could start the business of space tourism.