The moon of Jupiter is a good place to look for life. Evidence shows that the frozen moon is rich in life-enabling chemistry.

New research shows that the moon is pulling oxygen to the surface, where it could be feeding simple life.

The debate about whether or not life can be found in the ocean's surface is highly debatable, and the debate is stuck in neutral until NASA sends the Europa Clipper there. NASA bases part of the design of the Clipper mission on what scientists want it to address. We can't tell a spaceship to find life on a planet.

NASA can only answer small, specific questions when they design missions with big questions in mind. Scientists are studying different aspects of the planet and performing simulations to find out what questions they need to ask.

Oxygen is at the center of one of those questions. It could be the final piece in understanding habitability.

Most of what life needs to sustain itself is what we think Europa has. There is an abundance of water in the ocean. The oceans of Earth have less water than the waters of Europa. It also has the required vitamins. Life needs energy and it comes from Jupiter, which warms its interior and stops the ocean from freezing solid. Most scientists know these facts.

Oxygen is found at the frozen moon's surface, another hint of habitability. The moon's surface is covered with charged particles from Jupiter. The problem is that the ice sheet is a barrier between the ocean and oxygen. Any life would have to be in the ocean because the surface is frozen solid.

Oxygen makes its way from the surface to the ocean.

When charged particles strike Europa's surface, they split water molecules apart. The lighter hydrogen floats away into space, but the oxygen stays behind. If the oxygen somehow makes its way to the ocean, it could possibly provide chemical energy for microbial life. Image Credit: NASA
When charged particles strike Europa’s surface, they split water molecules apart. The lighter hydrogen floats away into space, but the oxygen stays behind. If the oxygen somehow makes its way to the ocean, it could provide chemical energy for microbial life. Image Credit: NASA

According to a new research letter, pools of saltwater in the icy shell could be transporting oxygen to the ocean. The research letter was published in the journal. The lead author is a professor at the UT Jackson School of Geosciences.

The briny pools are in places in the shell where some ice melt due to the ocean currents. Chaos forms above these pools.

Chaos terrain covers 25% of the frozen surface. There are ridges, cracks, faults, and plains in chaos terrain. There is no clear understanding of the causes of chaos terrain, and it is likely related to heating and melting. This feature is highlighted in some of the most famous images of Europa.

Image of Europa’s ice shell, taken by the Galileo spacecraft, of fractured “chaos terrain.” A tunnelling robot would likely be sent to this type of surface area. Image Credit: NASA/JPL-Caltech
Image of Europa’s ice shell, taken by the Galileo spacecraft, of fractured “chaos terrain.” Saltwater pools below chaos terrain may be transporting oxygen to the moon’s ocean. Image Credit: NASA/JPL-Caltech

Scientists think the ice sheet is 10 to 15 miles thick. A study found that chaos terrain can be found above lakes of liquid water as little as 3 km below the ice. The lakes are not directly connected to the ocean. The briny lakes can mix with surface oxygen and deliver large quantities of oxygen to the deeper ocean according to a new study.

This figure from the study shows how oxidants are generated and distributed in Europa's surface ice. Radiolysis sputters H2O into H2 and O, with O recombining into O2. Some of the O2 is released into the moon's atmosphere, but most of it returns to the icy regolith and is trapped in bubbles. The bubbles are the dominant near-surface reservoir for oxidants. Over thousands of years, the bubbles can make their way down to the ocean. Image Credit: Hesse et al. 2022.
This figure from the study shows how oxidants are generated and distributed in Europa’s surface ice. Radiolysis sputters H2O into H2 and O, with O recombining into O2. Some of the O2 is released into the moon’s atmosphere, but most of it returns to the icy regolith and is trapped in bubbles. The bubbles are the dominant near-surface reservoir for oxidants. Over thousands of years, the bubbles can make their way down to the ocean. Image Credit: Hesse et al. 2022.

The research puts this process into the realm of possibilities.

Oxygen is transported through the ice in a simulation. The brine moves to the ocean in a wave. A porosity wave transports the brine through the ice by widening the pores in the ice before it seals up again. The waves carry the oxygen-rich brine to the ocean.

The physics-based model built by the researchers shows a porosity wave (spherical shape) carrying brine and oxygen at Europa’s surface through the moon’s ice shell to the liquid water ocean below. The chart shows time (in thousands of years) and ice shell depth (in kilometres). Red indicates higher levels of oxygen. Blue represents lower levels of oxygen. Credit: Hesse et al. 2022

Oxygen transport and chaos terrain are not completely clear. Scientists think that the convective upwellings are caused by the partial melt of the ice. The ice under the brine must be molten or partially molten. The authors write that previous studies show that tidal heating increases the temperature of upwellings in the convecting portion of the ice shell.

It is plausible that the underlying ice is partially molten because of the chaotic terrains that form over diapiric upwellings. The connecting ice is likely to increase the melt.

Oxygen can't be transported in brines because the surface is not cold enough to refreeze. The temperature at the moon's poles is minus 220 C. The results of the model show that reoxidant at the surface is too slow to arrest the drainage of the brine. The research shows that the seafloor may be volcanic.

This illustration shows how volcanism in Europa's interior might work to maintain a liquid ocean. Credit: NASA/JPL-Caltech/Michael Carroll
This illustration shows how volcanism in Europa’s interior might work to maintain a liquid ocean. Credit: NASA/JPL-Caltech/Michael Carroll

The study says that most of the oxygen taken up at the surface makes it to the ocean. That percentage could have changed over the course of the moon's history. The model that produced the highest estimate creates an ocean that is very similar to Earth. Is something living under the ice?

Artist's impression of a hypothetical ocean cryobot (a robot capable of penetrating water ice) in Europa. Credit: NASA
Artist’s impression of a hypothetical ocean cryobot (a robot capable of penetrating water ice) in Europa. Credit: NASA

Steven Vance is a research scientist at NASA's Jet Propulsion Laboratory and the supervisor of the paper.

Kevin Hand is one of the many scientists who are interested in the potential for life and the upcoming Europa Clipper mission. Hand is a NASA/JPL scientist. He is hopeful that the problem of oxygen in the frozen moon's oceans has been solved by the researchers.

He asked if the compounds on the surface of the ocean could be used by life.

What questions can the Clipper ask to confirm the findings?

The Clipper is the first mission dedicated to the island. We have not been able to confirm many things about Europa. The Clipper addresses three larger objectives.

  • Investigate the ocean’s composition to determine if it has the necessary components to sustain life.
  • Investigate the moon’s geology to understand how the surface formed, including the chaos terrain.
  • Determine the ice shell’s thickness and if there’s liquid water within and beneath it. They also will determine how the ocean interacts with the surface: Does anything in the ocean rise through the shell to the top? Does any material from the surface work its way down into the ocean?

Oxygen can be transported from the surface to the ocean. The instruments that will work together to address these questions will be carried by the Europa Clipper.

When it comes to oxygen transport, the MAss SPectrometer is particularly interesting.

The chemistry of the surface, atmosphere, and suspected ocean are some of the important answers thatMASPEX will gain.

Oxygen could be transported from the surface to the ocean if life exists there. We will have to wait a while. The Jupiter system won't be reached until 5.5 years after the launch of the Europa Clipper. The science phase is expected to last four years. We don't have all the data yet.

We will be whetted by research like this.

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