Jupiter’s moon Europa is a top candidate for the search of life. The frozen moon has a sub-surface ocean, and proof shows it’s warm, salty, and good in life-enabling chemistry.
New research indicates that the moon is pulling oxygen down underneath its icy shell, in which it can be feeding simple life.
Whether or not Europa can maintain life in its sub-surface ocean is pretty debatable, and the debate is basically stuck in neutral till NASA sends the Europa Clipper there. The mission to Europa must be meticulously designed, and NASA bases a part of the design on what particular questions scientists need the Clipper to address. We can not send a spacecraft to Europa and inform it to find life.
NASA designs missions with enormous questions in mind, however they are able to just answer smaller, particular questions. So scientists are analyzing different factors of Europa and performing simulations to fine-tune the questions they want the mission to ask.
Oxygen is at the coronary heart of one of these questions. It is probably the very last piece in understanding Europa’s habitability.
Europa has, or we believe it has, greatest of what life requires to sustain itself. Water is the main ingredient, and it has an abundance of water in its sub-surface ocean. Europa has greater water than Earth’s oceans. It additionally has the needed chemical nutrients. Life requires energy, and Europa’s energy source is tidal flexing from Jupiter, that heats its interior and prevents the ocean from freezing solid. These are quite well-established facts to many scientists.
The frozen moon additionally has oxygen at its surface, any other fascinating trace of habitability. The oxygen is produced when sunlight and charged particles from Jupiter strike the moon’s surface. However, there’s a problem: Europa’s thick ice sheet is a barrier among oxygen and the ocean. Europa’s surface is frozen solid, so any life could need to be in its vast ocean.
How can oxygen create its way from the surface to the ocean?
According to a brand new research letter, saltwater pools in Europa’s icy shell may be transporting the oxygen from the surface to the ocean. The research letter is “Downward Oxidant Transport Through Europa’s Ice Shell through Density-Driven Brine Percolation,” published withinside the magazine Geophysical Research Letters. The lead author is Marc Hesse, a professor of the UT Jackson School of Geosciences Department of Geological Sciences.
These briny-pools exist in places withinside the shell in which some ice melts because of convection currents withinside the ocean. Europa’s well-known and photogenic chaos terrain forms above those pools.
Chaos terrain covers approximately 25 percent of Europa’s frozen surface. Chaos terrain is in which ridges, cracks, faults, and plains are jumbled together. There is no clear understanding of the precise reasons of chaos terrain, though it is possibly associated with uneven subsurface heating and melting. Some of Europa’s greatest iconic images spotlight this surprisingly stunning feature.
Scientists believe Europa’s ice sheet is approximately 15 to 25 km (10 to 15 miles) thick. A 2011 study discovered that chaos terrain on Europa can be located above large lakes of liquid water as little as 3 km (1.9 miles) under the ice. These lakes are not directly linked to the sub-surface ocean however can drain into them. According to this new study, the briny lakes can mix with surface oxygen and over time, can supply big portions of oxygen to the deeper subsurface ocean.
“Our research puts this process into the realm of the possible,” stated Hesse. “It offers a solution to what’s considered one of the outstanding problems of the habitability of the Europa sub-surface ocean.”
The researchers indicate how oxygen is transported via the ice in their simulation. The oxygen-laden brine moves to the sub-surface ocean in a porosity wave. A porosity wave transports the brine via the ice through momentarily widening the pores withinside the ice before quickly sealing up again. Over thousands of years, those porosity waves transport the oxygen-rich brine to the ocean.
The relationship among chaos terrain and oxygen transport isn’t absolutely clear. But scientists suppose that convective upwellings resulting from tidal heating partially melt the ice, manifesting because the jumbled chaos terrain at the surface. The ice below the brine should be molten or partially molten for the oxygen-rich brine to drain into the ocean. “For those brines to drain, the underlying ice should be permeable and therefore partially molten. Previous studies indicates that tidal heating rise the temperature of upwellings in the convecting part of Europa’s ice shell to the melting point of pure ice,” the authors write.
“Given that chaotic terrain probably form over diapiric upwellings, it’s possible that the underlying ice is partially molten,” the letter says. The presence of NaCl withinside the connecting ice probably will increase the melt.
Europa’s surface is bitterly cold however not cold sufficient to refreeze so fast that oxygen can not be transported in brines. At the moon’s poles, the temperature in no way rises above minus 220 C (370 F.) However, the model’s results “… demonstrate that refreezing on the surface is too slow to arrest the drainage of the brine and stop oxidant delivery to the internal ocean.” Though Europa’s surface ice is frozen solid, the ice below it is convective, that delays freezing. And some research indicates that the seafloor can be volcanic.
The study says that approximately 86 percent of the oxygen taken up at Europa’s surface makes it to the ocean. Over the moon’s history, that percent might have shifted widely. But the best estimate produced by the researchers’ model creates an oxygen-rich ocean very much like Earth’s. Could something be living below the ice?
“It’s enticing to think about some type of aerobic organisms living just below the ice,” stated co-author Steven Vance, a research scientist at NASA’s Jet Propulsion Laboratory (JPL) and the supervisor of its Planetary Interiors and Geophysics Group.
Kevin Hand is one among many scientists keenly interested in Europa, its capacity for life, and the upcoming Europa Clipper mission. Hand is a NASA/JPL scientist whose work make attention to Europa. He is hopeful that Hesse and his fellow researchers solved the problem of oxygen in the frozen moon’s oceans.
“We know that Europa has beneficial compounds like oxygen on its surface, however do those make it down into the ocean below, in which life can use them?” he asked. “In the work by Hesse and his collaborators, the answer appears to be yes.”
What questions can the Europa Clipper ask that would verify those findings?
The Clipper is the first mission devoted to Europa. We suppose we know many things about Europa that we have not been capable of confirm. The Clipper is designed to deal with 3 large objectives:
• Investigate the ocean’s composition to check if it has the essential components to sustain life.
• Investigate the moon’s geology to understand how the surface formed, which include the chaos terrain.
• Determine the ice shell’s thickness and if there is liquid water inside and below it. They will also check how the ocean interacts with the surface: Does whatever inside the ocean rise through the shell to the top? Does any material from the surface work its way down into the ocean?
That final factor speaks to the capacity transport of oxygen from the surface to the ocean. The Europa Clipper will bring ten instruments so that it will work collectively to deal with those questions.
The MAss SPectrometer for Planetary EXploration/Europa (MASPEX) is in particular thrilling when it comes to oxygen transport on Europa.
“MASPEX will benefit important answers from gases close to Europa, including the chemistry of Europa’s surface, atmosphere, and suspected ocean,” the instrument’s web page describes. “MASPEX will study how Jupiter’s radiation changes Europa’s surface compounds and how the surface and ocean exchange material.”
MASPEX, and the remaining of Europa Clipper’s instruments, would possibly verify oxygen transport from the surface to the ocean, in which life should use it if life exists there. But we will must wait a while. Europa Clipper is scheduled to launch in October 2024 and would not reach the Jupiter system till 5.5 years later. Once there, its science phase is predicted to last 4 years. So it may be 2034 before we’ve got all of the data.
In the meantime, research like this may whet our appetites.
This research was published in the journal Geophysical Research Letters.