Is Jupiter's moon Europa habitable? Its interior ocean might be able to sustain life, say NASA scientists
Scientists have unlocked a secret that could explain the origins of a liquid ocean hiding underneath the icy surface of Europa, one of Jupiter's 79 confirmed moons. The findings suggest that our best shot at finding alien life could be within our solar system.
According to NASA scientists, the moon may have generated enough heat to prevent the water beneath its surface from freezing. These findings, which have not been tested for errors yet, may help experts study other neighboring ocean worlds for habitable conditions. It also paves the way for future alien life hunting missions. "Europa is one of our best chances of finding life in our solar system. NASA's Europa Clipper mission will launch in the next few years, and so our work aims to prepare for the mission, which will investigate Europa's habitability," the space agency's planetary scientist Mohit Melwani Daswani says.
NASA's interest in Europa began over four decades ago when the Voyager spacecraft hurtled past it. Scientists have since gathered evidence that an ocean is present under the icy moon's surface. Information from the Galileo spacecraft, which reached Europa in 1996, helped provide hints of a subsurface ocean. It flew through a plume — liquid piercing through the moon's icy shell and bursting out, erupting like a huge geyser. Others have detected water vapor, which is a crucial ingredient to support life. Despite the advances, little was known about the origins and composition of this ocean.
Using data gathered from the Galileo mission, NASA's Daswani tried to figure out how water formed on Europa. Their analysis showed that the density of the moon's interior is a lot deeper than its outer layers. "That already tells us a really important property of Europa's history and geology: It must have experienced high heat for that process of differentiation to occur," Daswani tells Space.com. Differentiation allowed layers of ice and liquid water to take form in Europa, like it did on Earth.
But where did the heat come from? Two factors may have had a role in it: tidal movement due to Europa's interaction with nearby moons or early radioactive decay. The heat may have, in turn, triggered the breakdown of minerals bearing water, creating oceans. Based on these findings, the team speculates that oceans in other moons, such as Europa's neighbor Ganymede and Saturn's moon Titan, may also have a similar history. Daswani added that they are yet to understand how fluids migrate through Europa's rocky interior.
Life also depends on electrons, which provides energy for sustenance. "A long-standing question over whether a 'cloaked ocean' world like Europa could be habitable boils down to whether it can sustain a flow of electrons that might provide the energy to power life. What remains unclear is whether such icy moons could ever generate enough heat to melt rock; certainly, interesting chemistry takes place within these bodies, but what reliable flow of electrons could be used by alien life to power itself in the cold, dark depths? A key aspect that makes a world 'habitable' is an intrinsic ability to maintain these chemical disequilibria. Arguably, icy moons lack this ability, so this needs to be tested on any future mission to Europa," Professor Steve Mojzsis, Professor of Geology at the University of Colorado, who was not involved in the study, says.
The findings were presented at the 2020 Goldschmidt Conference.