A new study by a research team at Pasadena’s Jet Propulsion Laboratory suggests that Jupiter’s moon Europa might be able to support life even if there’s little or no volcanic activity under the satellite’s icy shell.
The study suggests that in the salty ocean of liquid water beneath Europa’s icy crust, there is enough energy that could support biological systems.
The team, led by Steve Vance, a planetary scientist who heads JPL’s Icy Worlds Astrobiology group, has found that, even without taking volcanic processes into account, Europa likely produces 10 times more oxygen than hydrogen, just like Earth does.
The team’s work is now drawing attention to the ways that Europa’s rocky interior may be much more complex and possibly Earth-like than most people think.
“We’re studying an alien ocean using methods developed to understand the movement of energy and nutrients in Earth’s own systems,” Vance says. “The cycling of oxygen and hydrogen in Europa’s ocean will be a major driver for Europa’s ocean chemistry and any life there, just as it is on Earth.”
Vance and his team ultimately desire to also understand the cycling of life’s other major elements in the ocean: carbon, nitrogen, phosphorus and sulfur.
As part of their study, the researchers calculated how much hydrogen that could be produced in Europa’s ocean as seawater reacts with rock, in a process called serpentinization. During this process, water percolates into spaces between mineral grains and reacts with the rock to form new minerals, releasing hydrogen in the process.
The other half of Europa’s chemical-energy-for-life equation would be provided by oxidants – oxygen and other compounds that could react with the hydrogen – being cycled into Europa’s ocean from the icy surface above. Europa is bathed in radiation from Jupiter, which splits apart water ice molecules to create these materials.
“The oxidants from the ice are like the positive terminal of a battery, and the chemicals from the seafloor, called reductants, are like the negative terminal. Whether or not life and biological processes complete the circuit is part of what motivates our exploration of Europa,” said Kevin Hand, another JPL planetary scientist who co-authored the study.
Scientists have long considered it possible that Europa might also have volcanic activity, like its neighboring Jovian moon Io, as well as hydrothermal vents, where mineral-laden hot water would emerge from the sea floor.
With the new study, Vance said even without the volcanic factor, the processes happening in Europa’s ocean could actually be balancing the oxidants in a ration comparable to that in Earth’s oceans.
Vance’s team is among the many NASA groups currently formulating a mission to explore Europa and investigate in depth whether the icy moon might be habitable.
Some time in the 2020s, NASA plans to send a highly capable, radiation-tolerant spacecraft into a long, looping orbit around Jupiter to perform repeated close flybys of Europa. During these flybys, the mission would take high-resolution images, determine the composition of the icy moon’s surface and faint atmosphere, and investigate its ice shell, ocean and interior.
For more information about NASA’s mission to Europa, visit www.nasa.gov/europa.