Once a star reaches the end of its life stage and becomes a red giant, any chance for life is extinguished. This is also true for our Sun, which is expected to turn into a red giant in about five billion years. When this happens, it will engulf Mercury, Venus, and likely Earth, turning them into smoldering wastelands. 

This catastrophic event will end all life on Earth, but according to a new study, this doesn’t mean our solar system would be entirely lifeless. The study authors suggest that while our world burns, Europe, one of Jupiter’s icy moons, could briefly become a warm, water-rich haven, potentially supporting life for up to 200 million years after our Sun’s death.

“It is possible that in a fiery, dramatic end to one part of the system, life could find new beginnings,” the study authors said. For instance, “a majority of habitable terrestrial planets, including ours, will one day face their inevitable end in the red giant branch. However, icy moons in our solar system and around other stars could evolve into a habitable world,” they added. 

Decoding the possibility of life on Europa

When a star like our Sun exhausts the hydrogen in its core, the process of nuclear fusion slows down. This triggers the core to shrink and the outer layers to balloon outward, transforming the star into a red giant that is hundreds of times larger and far more luminous than before. 

During this phase, the Sun could scorch the inner planets and evaporate Earth’s oceans, turning it into a charred and dead space rock. To understand how this transformation might affect the rest of the solar system, researchers at Cornell University’s Carl Sagan Institute ran simulations.

They predicted how the Sun’s increased brightness and heat would impact the outer planets and their moons. This is when they come across some interesting scenarios shaping Europa into a potential site for life.

During the red giant phase, both the Sun and Jupiter will shine brighter and become hotter. However, its moon Europa is tidally locked and therefore heats up unevenly. For instance, the side of the moon facing Jupiter would heat up the most, because it would receive extra radiation reflected from the now-brighter gas giant. 

This intense heat would cause Europa’s surface ice to sublimate, a process where ice turns directly into vapor. Meanwhile, the liquid ocean below the hundreds-of-miles-thick ice sheet would begin to evaporate. Most of the water would be lost from the areas facing Jupiter and from the equatorial regions. 

However,  interestingly, the northern and southern latitudes on the far side of Europa, the side facing away from Jupiter, would heat more gently. These regions would lose water more slowly, creating a thin but stable atmosphere of water vapor that could last up to 200 million years. Computer simulations suggest that during this time, Europa’s surface might temporarily resemble conditions suitable for life.

A new perspective on life in the universe

For a long time, scientists believed that once the Sun becomes a red giant, the solar system would no longer be able to support life. However, new findings paint a more optimistic picture. It now appears that even after the Sun begins to die, icy moons like Europa could briefly become habitable oases.

This might also be true for many other icy moons located in other solar systems as well. Until now, these cosmic entities were considered too cold and dark to support life. However, the new research sheds light on the important role these frozen worlds could play amid the death of the Sun and many other planets in the solar system.

The study authors now plan to apply their models to other icy moons and see whether some could be candidates for the next havens of life across the universe. 

The study was published in the journal arXiv.