New theory suggests Europa has an oxygen-rich ocean much like Earth’s

(ORDO NEWS) — Jupiter’s moon Europa is a prime candidate for the search for life. The frozen moon has a subsurface ocean that data shows is warm, salty, and rich in life-promoting chemicals.

New research shows that the moon is pulling oxygen down under its icy shell, where it can fuel simple life.

The question of whether Europa can support life in its subsurface ocean is highly debatable, and the debate is essentially neutral until NASA sends the Europa Clipper there.

A mission to Europa must be carefully designed, and NASA bases part of the design on what specific questions the scientists want the Clipper to explore. We can’t send a spacecraft to Europa and ask it to find life.

NASA designs missions with big questions in mind, but they can only answer smaller, specific questions. Therefore, scientists study various aspects of Europe and conduct simulations to refine the questions that the mission should answer.

One of these issues is oxygen. It may be the last detail in understanding Europe’s habitability.

Europa has, or we think it has, almost everything that is needed to sustain life. Water is the main ingredient and is found in abundance in its subsurface ocean. Europa has more water than Earth’s oceans.

It also has essential chemical nutrients. Life needs energy, and the source of energy for Europa is Jupiter’s tidal action, which heats its interior and keeps the ocean from freezing. For most scientists, these are well-established facts.

The frozen moon also has oxygen on its surface, another intriguing hint at the possibility of habitability. Oxygen is produced when sunlight and charged particles from Jupiter hit the surface of the moon.

But there’s a problem: Europa’s thick ice sheet is a barrier between oxygen and the ocean. The surface of Europa is covered with ice, so any life must be in its vast ocean.

How can oxygen get from the surface into the ocean?

Pools of salt water in Europa’s icy shell could carry oxygen from the surface to the ocean, according to a new science letter. The study, titled “Downward Transport of Oxidizers Through the Europa Ice Shell by Density Driven Brine Percolation,” is published in Geophysical Research Letters.

The lead author is Mark Hesse, Professor in the Department of Geological Sciences at the UT Jackson School of Geosciences.

These salt pools exist in areas of the shell where some of the ice is melting due to convection currents in the ocean. Above these basins, the famous and photogenic chaos of Europe is formed.

New theory suggests Europa has an oxygen rich ocean much like Earths 1

The relief of chaos covers about 25 percent of Europa’s frozen surface. Chaos relief is when ridges, fissures, faults and plains are mixed together.

So far, there is no clear understanding of the exact causes of chaos, but, most likely, it is associated with uneven heating and melting of the subsurface layer. Some of Europe’s most iconic shots showcase this extraordinarily beautiful feature.

Scientists believe that the Europa ice sheet is between 15 and 25 kilometers (10 to 15 miles) thick. A 2011 study showed that the chaotic terrain on Europa could be over huge lakes of liquid water just 3 kilometers (1.9 miles) below the ice.

These lakes are not directly connected to the subsurface ocean, but may flow into it. Liquid lakes can mix with surface oxygen and deliver large amounts of oxygen to the deeper subsurface ocean over time, according to a new study.

“Our research takes this process into the realm of the possible,” Hesse said. “It provides a solution to what is considered to be one of the unsolved habitability problems in Europe’s subsurface ocean.”

The researchers showed how oxygen is transported through ice in their simulations.

New theory suggests Europa has an oxygen rich ocean much like Earths 2

Above: This figure shows how oxidizers are generated and distributed in Europa’s surface ice. Radiolysis splits H2O into H2 and O, while O recombines into O2.

Some of the O2 is expelled into the lunar atmosphere, but most is returned to the icy regolith and trapped in bubbles. Bubbles are the dominant near-surface reservoir for oxidizers. Over thousands of years, bubbles can end up in the ocean.

The oxygenated brine moves into the subsurface ocean in a wave of porosity. A wave of porosity carries the brine through the ice, momentarily expanding the pores in the ice and then quickly sealing them back up again. Over thousands of years, these waves of porosity carry oxygen-rich brine into the ocean.

The relationship between chaotic relief and oxygen transport is not completely clear. But scientists believe that the convective uplift caused by tidal heating is partially melting the ice, manifesting itself as chaos on the surface. The ice under the brine must be melted or partially melted so that the oxygen-rich brine can drain into the ocean.

“In order for these brines to drain, the underlying ice must be permeable and therefore partially molten. Previous studies show that tidal heating raises the upwelling temperature in the convecting portion of the Europa ice sheet to the melting temperature of pure ice,” the authors write.

“Given that chaotic reliefs are likely to form above the diapiric upwells, it can be assumed that the underlying ice is partially melted,” the letter says. The presence of NaCl in the bonding ice probably enhances melting.”

Europa’s surface is very cold, but not so cold that it freezes so quickly that oxygen cannot be carried in the brines. Temperatures never rise above minus 220 C (370 F.) at the Moon’s poles.

But the results of the model “…show that surface freezing is too slow to stop brine drainage and prevent delivery of oxidants to the inland ocean.”

Although Europa’s surface ice is firmly frozen, the ice underneath is convective, which delays freezing. And some studies show that the seabed may be volcanic.

The study says that about 86 percent of the oxygen absorbed on Europa’s surface ends up in the ocean. Over the history of the moon, this percentage could change dramatically.

But the highest score obtained by the researchers’ model creates an oxygen-rich ocean much like Earth’s. Can something live under the ice?

“It’s tempting to think that some kind of aerobic organisms live under the ice,” said study co-author Stephen Vance, a NASA Jet Propulsion Laboratory (JPL) scientist and leader of the Planetary Interiors and Geophysics Group.

Kevin Hand is one of many scientists with a strong interest in Europa, its potential for life, and the upcoming Europa Clipper mission. Hand is a NASA/JPL scientist whose work focuses on Europe. He hopes that Hess and his fellow researchers have solved the problem of oxygen in the oceans of the frozen moon.

“We know that there are useful compounds like oxygen on Europa’s surface, but do they end up in the ocean where life can use them?” he asks. “In the work of Hess and his colleagues, the answer seems to be yes.”

What questions can Europa Clipper ask to support these findings?

The Clipper is the first mission designed to explore Europe. We think we know a lot about Europe that we haven’t been able to confirm yet. The Clipper is designed to solve three big problems:

– Examine the composition of the ocean to determine if it contains the ingredients needed to sustain life.
– Explore the geology of the moon to understand how its surface was formed, including the chaotic topography.
– Determine the thickness of the ice shell and find out if there is liquid water inside and under it. They will also determine how the ocean interacts with the surface: Does anything in the ocean rise up through the shell? Does any material from the surface end up in the ocean?

The latter refers to the potential transfer of oxygen from the surface to the ocean. The Europa Clipper will carry ten instruments that will work together to answer these questions.

The MAss SPectrometer for Planetary EXploration/Europa (MASPEX) is of particular interest when it comes to oxygen transport on Europa.

“MASPEX will provide critical answers from gases near Europa, such as the chemistry of Europa’s surface, atmosphere and proposed ocean,” the instrument’s web page explains. “MASPEX will study how Jupiter’s radiation changes Europa’s surface connections and how the surface and ocean exchange materials.”

MASPEX and the rest of the Europa Clipper instruments can confirm the transfer of oxygen from the surface to the ocean, where it can be used by life, if it exists there.

But we will have to wait a while.

The launch of Europa Clipper is scheduled for October 2024, and it will reach the Jupiter system only after 5.5 years. The scientific phase of the flight is expected to last four years. So it could be 2034 before we get all the data.


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