Is there life on the oceanic moon Europa of Jupiter? This moon has fascinated space enthusiasts for decades, as scientists have determined that there is a global ocean of water beneath the moon’s outer frozen crust. Last week (June 24, 2020), NASA scientists announced new research to support the idea that the ocean of Europe is habitable. They said that this underground ocean is probably similar in many ways to the oceans outdoors on Earth.
The fascinating results were presented at the Goldschmidt conference (virtual thanks to Covid-19 this year). The associated abstract is available on the conference website. These are preliminary and not yet peer-reviewed results.
First, the results support what scientists predicted about the composition of the ocean, as planetary scientist and chief researcher Mohit Melwani Daswani explained in a statement:
We were able to model the composition and physical properties of the core, the silicate layer and the ocean. We find that different minerals lose water and volatile substances at different depths and temperatures. We added these birds that are estimated to have been lost from the inside and found that they are consistent with the expected mass of the current ocean, which means they are probably present in the ocean.
To reach this conclusion, the researchers modeled the geochemical basins within Europe using data from the old Galileo mission. The results are significant because they show that oceans like the one on Europe can be formed by metamorphism, that is, by a change of minerals or by a distinct arrangement of minerals (a change in what geologists call texture) in pre-existing rocks (protoliths) without the protolite dissolves in liquid magma.
On Europe, the warming and rising pressure caused by early radioactive decay or subsequent tidal movement of the subsoil would have caused a breakdown of the minerals containing water. The trapped water would be released and the underground ocean of Europe would be born.
And what about habitability?
The study also found that the ocean of Europe was initially slightly acidic, with high concentrations of carbon dioxide, calcium and sulfate. But over time it has become rich in chloride, similar to the oceans on Earth (sea water on Earth contains 1.94% chloride). According to Daswani:
In fact it was thought that this ocean could still be quite sulfuric, but our simulations, combined with data from the Hubble Space Telescope, which showed chloride on the surface of Europa, suggest that the water most likely became rich in chloride. In other words, its composition became more similar to the oceans on Earth. We believe that this ocean could be quite habitable for life.
Europe is one of our best chances to find life in our solar system. NASA’s Europa Clipper mission will be launched in the coming years, and therefore our work aims to prepare us for the mission, which will investigate the habitability of Europa. Our models lead us to think that the oceans of other moons, such as the nearby Europe of Ganymede and the moon of Titan of Saturn, may also have formed with similar processes.
We still need to understand several points, such as how fluids migrate through the rocky interior of Europa.
Another interesting possibility is that volcanic vents on the ocean floor of Europe’s ocean may have contributed to the chloride enrichment process of the water. It would be exciting, since such vents on Earth provide heat and nutrients to a wide variety of life in the deep oceans of our world.
The Cassini spacecraft has already found evidence for such vents on the seabed of Saturn’s moon Enceladus, which also has a global ocean under its frozen crust.
These or other sources of energy would be necessary for life to evolve and thrive in an underground ocean: a dark and sunless environment. As Steve Mojzsis, a professor of geology at the University of Colorado Boulder, observed:
A long-standing question about whether a “hidden ocean” world like Europe can be habitable boils down to whether it can sustain an electron flow that could provide the energy to fuel life. What remains unclear is whether such frozen moons can ever generate enough heat to melt the rock; within these bodies a definitely interesting chemistry takes place, but what reliable flow of electrons could be used by alien life to feed on the cold and dark depths?
A key aspect that makes a world “habitable” is the intrinsic ability to maintain these chemical imbalances. Probably, frozen moons do not have this capability, so this must be tested in any future mission in Europe.
The results of the new study are tempting, but more work needs to be done. How much chloride is there really in the ocean of Europe? As mentioned in an article dated June 25, 2020 Centauri Dreams, a 2019 document states the following about sodium chloride (NaCl) on Europe:
The presence of NaCl on Europe has important implications for our understanding of internal chemistry and its geochemical evolution over time. While the aqueous differentiation of the chondritic material and the long-term leaching from a chondritic seabed can result in a sulfate-rich system, a more extensive hydrothermal circulation, as on Earth, can lead to an ocean rich in NaCl. The chemistry of the plume of Enceladus, which is perhaps the best analogue in Europe, suggests an ocean dominated by NaCl and a hydrothermically active seabed. However, the compositional relationship between the ocean of Europe and its endogenous material is unknown and the surface can simply represent the final result of a compositional stratification within the ice shell … Regardless of whether the observed NaCl is directly related to the composition of the ocean, its presence guarantees a reassessment of our understanding of the geochemistry of Europe.
Scientists can learn more about the ocean of Europe by modeling, but obtaining concrete evidence will actually require sending a mission there. Fortunately, NASA’s Europa Clipper mission is set to do just that, which is slated to launch in 2023.
Europe is one of the largest moons in the solar system with a diameter of 1,926 miles (3,100 km), just under the moon on Earth. While the underground ocean is relatively warm (exact temperature not yet known), temperatures on Europe’s almost airless surface are always bitter minus 256 degrees Fahrenheit (minus 160 degrees Celsius) or less.
There is also growing evidence of water vapor plumes over Europe, similar to those on Saturn’s moon Enceladus. If they are there, Europa Clipper could fly through them, just like Cassini did in Enceladus, and sample the steam for analysis. If connected to the ocean, as Enceladus is thought to be, it would provide valuable clues about conditions in the European ocean and, perhaps, even about the test of life itself.
The latest analysis of the ocean of Europe is tempting, but we will know much more after Europa Clipper – and ESA’s Jupiter Icy Moon Explorer (JUICE) mission – we will look more closely in the years to come.
In conclusion: a new study conducted by NASA scientists shows that the ocean of Europe is habitable.
Source: evolution of birds from within Europe into its ocean
Via Astrobiology Web