- NASA's Juno mission found that Jupiter's icy moon Europa produces 1,000 tons of oxygen every 24 hours.
- It's enough to keep a million people breathing for a day, but it's much lower than previously thought.
- This new data may narrow the odds that Europa supports life in its vast underground ocean.
About 400 million miles away, floating in deep space is a watery world called Europa, producing 1,000 tons of oxygen every 24 hours. That's enough oxygen to keep a million people alive for one day. NASA reported this week.
However, these new estimates have been published in the peer-reviewed journal Nature astronomyIt is not intended to limit the number of people that could inhabit this moon of Jupiter. They help scientists figure out whether Europa is hosting life of its own.
“We think Europa is the most likely place to look beyond Earth for life today,” said Kurt Niebuhr, NASA's principal scientist for exoplanet exploration who was not involved in the study.
If life forms exist on Europa, they might look like microbes, or perhaps something more complex. According to NASA. But it will not be visible from the surface, as it is a frozen desert.
It is likely to be found in the moon's vast underground ocean, which may contain twice the amount of water found on Earth.
While water is one of the essential elements of life, as we know it, it is not the only element. There is a long list of other chemicals that scientists are looking for, and oxygen is one of them.
Now, NASA's Juno spacecraft, currently flying around Jupiter and its moons, has taken the most accurate estimate of Europa's oxygen production to date. It turns out to be much lower than we thought.
The latest estimate is 1,000 tons of oxygen every 24 hours, which is more than 86 times less than some previous estimates. This new data may call into question Europe's habitability.
How does Europe produce oxygen?
Oxygen production looks very different on Europa than on Earth. While Earth gets its oxygen from photosynthesis, Europa is the result of its parent planet Jupiter.
Jupiter emits powerful radiation that showers Europe with high-energy particles. These particles then interact with frozen water ice (H2O) on the moon's surface.
The reaction splits H2O molecules into hydrogen and oxygen gas. But where does this oxygen go is the big question. Some might get stuck in the ice, some might escape into space, and some might even travel to the ocean beneath Europa's surface.
If enough oxygen reaches underground, it would mean that Europa's ocean contains one of the vital ingredients for life as we know it. “But this is a big question mark for us,” Niebuhr said, because oxygen can end up in many different places.
What NASA's Juno mission did was shed more light on the total amount of oxygen generated by Europa's surface. However, it is still unclear how much, if any, is leaking into the underground ocean.
Oxygen measurement over Europe
To measure the amount of oxygen generated by Europa's surface, scientists used the Jovian Aurora Distributions Experiment (JADE) instrument on board Juno.
JADE is designed to measure charged particles in Jupiter's auroral regions. But when Juno flew by Europa in September 2022, JADE successfully measured charged particles emitted from the moon's atmosphere for the first time.
Using JADE data, scientists estimated the total amount of hydrogen gas (but not oxygen) in Europe's thin atmosphere. Because there is one oxygen atom for every two hydrogen atoms in a water molecule, scientists can use hydrogen gas data to calculate the amount of oxygen generated at the surface.
“This has improved and narrowed our understanding of how much oxygen is synthesized at the surface,” said the study's lead author, Jami Salai, a space physicist at Princeton University.
“But we don’t know how much of it leaves the surface and how much of it makes its way into the ocean,” Salai added. NASA's upcoming Clipper mission to Europa may bring us closer to answering this question.
A constant search for the possibility of life
NASA's Europa Clipper mission is scheduled to launch in October 2024. Its primary goal is to determine whether Europa is habitable or not.
Clipper will be equipped with instruments that will help reveal Europa's internal structure, such as subsurface radar. Using this tool, NASA scientists will drill dozens of miles below the crust to identify features that could help determine whether oxygen is reaching the subsurface ocean, Niebuhr told BI.
“Clipper is an incredibly exciting mission, with important scientific goals that are likely to revolutionize our understanding of the ice crust, the subsurface ocean, and how they interact with each other,” Szalay said.
While knowing whether or not Europa's subsurface ocean contains oxygen would improve our understanding of the moon's habitability, it would not automatically confirm whether life exists, or can exist, on Europa.
“The amount of oxygen available on Europa is not a binary switch that you can flip to decide whether life is possible or not,” Niebuhr explained.
He pointed out that life has existed on Earth for about 1.5 billion years without oxygen. If it could happen here, it could happen on this distant moon, too.
As for the Juno mission, Szalay will continue to work from the data he recovered during this flyby of Europa.
“For years to come, we will be researching this and learning everything we can,” he said.
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