By building the world’s first physics-based computer simulation of the process, scientists from the University of Texas at Austin tested a theory that suggests Jupiter’s moon Europa may be habitable if radiolytic oxidants are generated at its surface travel efficiently through the ice.
Jupiter’s moon Europa is thought to have an ocean beneath its ice shell. The habitability of the internal ocean depends on the availability of redox gradients. The theories claim that saltwater within the icy shell of Jupiter’s moon Europa could be transporting oxygen into an ice-covered ocean of liquid water. There it could sustain life.
Scientists tested the theory by creating simulations of the process with oxygen rising on saltwater under the moon’s “chaos terrains”. These chaos terrains are landscapes of cracks, ridges, and ice blocks covering a quarter of the icy world.
Their simulation shows the possibility of oxygen transfer. Scientists also found that the amount of oxygen brought into Europa’s ocean could be similar to the quantity of oxygen in Earth’s oceans today.
Lead researcher Marc Hesse, a professor at the UT Jackson School of Geosciences Department of Geological Sciences, said, “Our research puts this process into the realm of the possible. It provides a solution to one of the great problems of the habitability of the Europa subsurface ocean.”
The ice shell of Europa is estimated to be about 15 miles thick. This shell is a barrier between water and oxygen- generated by sunlight and charged particles from Jupiter striking the icy surface.
Is there life in the ocean? If yes, there should be a way for oxygen to get to it. Hesse thinks the plausible scenario based on the available evidence is that the oxygen is carried by salt water or brine.
According to scientists, the chaos terrains form the surface regions where Europa’s ice shell partially melts to form brine. This brine can mix with oxygen from the surface.
The new model showed what happens to the brine after forming the Chaos terrain. It also shows that the brine drains uniquely: It takes the form of a porosity wave, causing pores in the ice to momentarily widen – allowing the brine to pass through before sealing back up.
This way effectively brings oxygen through the ice. 86% of the oxygen taken up at the surface riding the wave to the ocean.
Steven Vance, a research scientist at NASA’s Jet Propulsion Laboratory (JPL), said, “The highest estimate would make the oxygen levels in Europa’s ocean similar to those in Earth’s oceans – which raises hope about the potential for that oxygen to support life in the hidden sea.”
“It’s enticing to think of some kind of aerobic organisms living just under the ice.”
Kevin Hand, a scientist, who focused on Europa research at NASA JPL, who was not part of the study, said that the study presents a compelling explanation for oxygen transport on Europa.
“We know that Europa has useful compounds like oxygen on its surface, but do those make it down into the ocean below, where life can use them? In work by Hesse and his collaborators, the answer seems to be yes.”
- Marc A. Hesse et al. Downward Oxidant Transport Through Europa’s Ice Shell by Density-Driven Brine Percolation. DOI: 10.1029/2021GL095416