At first glance, Jupiter’s moon Europa doesn’t look much like Earth. It is a moon, not a planet, and it is covered in ice. But it has one important thing in common with Earth: a warm, salty ocean.
There is now even more evidence that Europe’s underground ocean is habitable.
NASA scientists have developed a new model that supports Europe’s ability to support life. They presented their work at the Goldschmidt 2020 Conference, an annual conference on geochemistry and similar topics. It is organized by the European Geochemical Association and the Geochemical Society.
“We believe this ocean could be quite habitable for life.”
M. Melwani Daswani, lead author, JPL.
The work is titled “Evolution of volatiles from the interior of Europe to its ocean”. The authors are M. Melwani Daswani and SD Vance, from the Jet Propulsion Laboratory. Their work has not yet been peer reviewed.
Europe is one of Jupiter’s Galilean moons, the smallest of the four. His brothers Ganymede and Callisto can also harbor oceans below the surface, while the fourth moon, Io, cannot.
The ocean of Europe is buried under a frozen crust approximately 10-30 km (6-19 miles) thick, and a liquid ocean below that may be 100 km (62 miles) thick. The probable source of heat for this liquid is the flexing of the tides due to the monstrous mass of Jupiter and the orbital resonance of Europe with the other Galilean moons. Evidence for this ocean dates back to the Voyager and Galileo spacecraft.
This new research presented at the Goldschmidt Conference suggests that this underground ocean was formed endogenously. That means it was formed by the decomposition of water-containing minerals due to tidal forces or radioactive decay. That opposes an exogenous ocean like Earth, which was probably sent to Earth by comets and / or asteroids.
This work is based primarily on data from the Galileo mission, which arrived at Jupiter in 1995. Galileo made a series of orbits for Jupiter and some of its moons, and the mission ended when it was exorbitant on Jupiter in 2003. But images from the space telescope Hubble also played an important role.
“We were able to model the composition and physical properties of the core, the silicate layer and the ocean,” lead author Daswani said in a press release. “We found that different minerals lose water and volatiles at different depths and temperatures. We add these volatiles that are estimated to have been lost from the interior, and we discovered that they are consistent with the predicted mass of the current ocean, which means that they are probably present in the ocean. “
While many researchers think that tidal flexing is responsible for warming, radioactive decay may also play a role. But whatever the source, as heat and pressure increased within Europe, minerals that contain water decompose and release that water.
Some scientific ideas say that water may be too acidic for life as we know it, due to the higher concentrations of calcium, sulfate and carbon dioxide. But this new model suggests that that was temporary, and the ocean grew rich in chloride over time.
“Europe is one of our best opportunities to find life in our solar system.”
M. MELWANI DASWANI, PRINCIPAL AUTHOR, JPL.
“In fact, it was thought that this ocean could still be quite sulfuric,” said Daswani, “but our simulations, along with data from the Hubble Space Telescope, showing chloride on the surface of Europe, suggest that the water probably became rich in chloride”. In other words, its composition was more like Earth’s oceans. We believe this ocean could be quite habitable for life. “
Habitable is one thing, but inhabited is another. And that’s why so much thought is given to a mission to Europe to investigate further.
“Europe is one of our best opportunities to find life in our solar system. NASA’s Europa Clipper mission will launch in the coming years, so our work aims to prepare for the mission, which will investigate the habitability of Europe, ”said Daswani. “Our models lead us to think that the oceans on other moons, such as Europe’s neighbor Ganymede, and Saturn’s moon Titan, may also have been formed by similar processes. However, we still need to understand several points, such as how fluids migrate through the rocky interior of Europe. “
“… What reliable flow of electrons could alien life use to feed in the cold, dark depths?”
Steve Mojzsis, professor of geology at the University of Colorado.
The issue of habitability could be reduced to one question. And it’s something that can only be answered by sending a spaceship to the moon. In a press release, Steve Mojzsis, a professor of geology at the University of Colorado, framed that question as an independent commenter not involved in the research.
“A long-standing question about whether a ‘covert ocean’ world like Europe could be livable boils down to whether it can sustain a flow of electrons that could provide the energy to fuel life. What is unclear is whether such icy moons They could generate enough heat to melt rocks; certainly, interesting chemistry is produced within these bodies, but what reliable flow of electrons could extraterrestrial life use to feed in the cold, dark depths? A key aspect that makes a world “habitable” is the intrinsic ability to maintain these chemical imbalances. Icy moons arguably lack this ability, so it must be tested on any future mission to Europe. “
The surface of Europe is an icy place. The temperature at the equator averages approximately 110 K (? 160 ° C ;? 260 ° F) and only about 50 K (? 220 ° C ;? 370 ° F) at the poles. That means that its surface is as hard as rock. But although scientists know that the ocean below the surface is warm, they don’t know its temperature.
Right now we only have a tantalizing taste of the nature of Europe’s ocean. There will be more studies and more models and simulations as time goes by, and that work is necessary. But only a mission to the moon can really answer our questions. (And it will probably raise a few more questions, too.)
While Europa Clipper will be just an orbiter, other concept missions go further. One concept requires a nuclear powered tunnel robot to traverse ice and study the ocean itself. Another suggested boring through the laser ice to get to the ocean. But those ideas are fancy, for now, and face many obstacles.
We will trust the Clipper to answer our questions about Europe and its ocean. And unfortunately, we are going to have to wait a few years for that.
