Beyond “Fermi’s Paradox” XIII: What is the “Ocean Worlds” Hypothesis?

The "ocean worlds" of the Solar System. Credit: NASA/JPL

Welcome back to our Fermi Paradox series, where we take a look at possible resolutions to Enrico Fermi’s famous question, “Where Is Everybody?” Today, we examine the possibility that the reason for the Great Silence is that most life out there exists in warm water oceans under sheets of ice!

In 1950, Italian-American physicist Enrico Fermi sat down to lunch with some of his colleagues at the Los Alamos National Laboratory, where he had worked five years prior as part of the Manhattan Project. According to various accounts, the conversation turned to aliens and the recent spate of UFOs. Into this, Fermi issued a statement that would go down in the annals of history: “Where is everybody?

This became the basis of the Fermi Paradox, which refers to the disparity between high probability estimates for the existence of extraterrestrial intelligence (ETI) and the apparent lack of evidence. Since Fermi’s time, there have been several proposed resolutions to his question, which include the possibility that Oceans Worlds (and not rocky planets) might be the best candidates for finding life.

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Geysers on Europa might come from pockets of water under the ice

Artist's conception of a cryovolcanic eruption on Europa. Credit: Justice Blaine Wainwright

Observations have already confirmed the existence of a sub-surface ocean on Europa, and there has been rampant speculation about whether they could contain life.  While there have been tentative plans to send a submersible spacecraft to this ocean, we are still a long way from uncovering what lies in those depths.

Which is one big reason why the geysers that occasionally shoot out of Europa’s ice sheet have garnered such interest.  Scientists hoped that some of the ejected water could come from that ocean.  It could then be sampled with a simple fly-by mission, such as Europa Clipper, rather than a submersible craft.  However, a new paper published in Geophysical Research Letters suggests a much more mundane source of the geysers – local liquid water buried in the moon’s thick ice shelf.

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Europa’s Nightside Glows in the Dark

This illustration of Jupiter's moon Europa shows how the icy surface may glow on its nightside, the side facing away from the Sun. Variations in the glow and the color of the glow itself could reveal information about the composition of ice on Europa's surface. Credit: NASA/JPL-Caltech

In a few years, NASA will be sending a spacecraft to explore Jupiter’s icy moon Europa. Known as the Europa Clipper mission, this orbiter will examine the surface more closely to search for plume activity and evidence of biosignatures. Such a find could answer the burning question of whether or not there is life within this moon, which is something scientists have speculated about since the 1970s.

In anticipation of this mission, scientists continue to anticipate what it will find once it gets there. For instance, scientists from NASA’s Jet Propulsion Laboratory recently conducted a study that showed how Europa might glow in the dark. This could be the result of Europa constantly being pummeled with high-energy radiation from Jupiter’s magnetic field, the study of which could tell scientists more about the composition of Europa’s ice.

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The Newest Picture of Jupiter and Europa Captured by Hubble

This latest image of Jupiter, taken by the NASA/ESA Hubble Space Telescope on 25 August 2020, was captured when the planet was 653 million kilometres from Earth. Hubble’s sharp view is giving researchers an updated weather report on the monster planet’s turbulent atmosphere, including a remarkable new storm brewing, and a cousin of the Great Red Spot changing colour — again. The new image also features Jupiter’s icy moon Europa. Credit: NASA, ESA, A. Simon (Goddard Space Flight Center), and M. H. Wong (University of California, Berkeley) and the OPAL team.

The venerable Hubble Space Telescope has given us another gorgeous picture of Jupiter and its moon Europa. The incredibly sharp image was captured on August 25th, and shows some of the stunning detail in Jupiter’s stormy atmosphere. Hidden in all that stormy activity is something new: a bright white storm plume travelling at about 560 km/h (350 mp/h).

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NASA Releases a New Poster for the Europa Clipper Mission

Credit: NASA/JPL-Caltech

In this decade and the next, some very impressive missions will take place. For instance, NASA will send its robotic Europa Clipper orbiter investigate Jupiter’s icy moon Europa for the first time. The orbiter will launch sometime in the middle of the decade (likely 2024) and arrive in the Jovian sytem in the 2030s to look for possible signs of life.

In preparation for this momentous event, NASA recently released a stunning new mission poster. As you can see, the poster features the orbiter looking down on Europa’s icy surface with Jupiter hanging in the background. The orbiter itself is in shadow so as to draw attention to the landscape beneath it.

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Europa’s entire icy shell shifted 70-degrees a few million years ago

Images from NASA's Galileo spacecraft show the intricate detail of Europa's icy surface. Image: NASA/JPL-Caltech

The mysterious world Europa, the ice-covered second moon of Jupiter, sports deep scars that cut across its face. An international team of investigators studied high-resolution maps of that surface to reveal a pattern: something shook Europa sometime within the past few million years, causing the entire shell to shift by 70 degrees.

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More Evidence that Europa’s Oceans Could be Habitable

A "true color" image of the surface of Jupiter's moon Europa as seen by the Galileo spacecraft. In 2030, the Europa Clipper mission will start its close flybys of this ocean world. Image credit: NASA/JPL-Caltech/SETI Institute
A "true color" image of the surface of Jupiter's moon Europa as seen by the Galileo spacecraft. In 2030, the Europa Clipper mission will start its close flybys of this ocean world. Image credit: NASA/JPL-Caltech/SETI Institute

At first glance, Jupiter’s moon Europa doesn’t seem much like Earth. It’s a moon, not a planet, and it’s covered in ice. But it does have one important thing in common with Earth: a warm, salty ocean.

Now there’s even more evidence that Europa’s sub-surface ocean is habitable.

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Planets With Large Oceans are Probably Common in the Milky Way

The "ocean worlds" of the Solar System. Credit: NASA/JPL

Within our Solar Systems, there are several moons where astronomers believe life could be found. This includes Ceres, Callisto, Europa, Ganymede, Enceladus, Titan, and maybe Dione, Mimas, Triton, and the dwarf planet Pluto. These “ocean worlds” are believed to have abundant liquid water in their interiors, as well as organic molecules and tidal heating – the basic ingredients for life.

Which raises the all-important question: are similar moons to be found in other star systems? This is the question NASA planetary scientist Dr. Lynnae C. Quick and her team from NASA’s Goddard Space Flight Center sought to address. In a recent study, Quick and her colleagues examined a sample of exoplanet systems and found that ocean worlds are likely to be very common in our galaxy.

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Even More Evidence that Europa has Geysers

A "true color" image of the surface of Jupiter's moon Europa as seen by the Galileo spacecraft. In 2030, the Europa Clipper mission will start its close flybys of this ocean world. Image credit: NASA/JPL-Caltech/SETI Institute
A "true color" image of the surface of Jupiter's moon Europa as seen by the Galileo spacecraft. In 2030, the Europa Clipper mission will start its close flybys of this ocean world. Image credit: NASA/JPL-Caltech/SETI Institute

Earlier this week, we shared some stunning, newly reprocessed images of Europa from NASA’s Galileo spacecraft, which visited Jupiter and its moons from December 1995 to September 2003. Now, as scientists continue to revisit Galileo’s data, even more details are coming into focus about Jupiter’s enticing moon. Not only is there evidence within the past few years of geysers shooting from Europa’s surface, twenty years ago, Galileo may have also witnessed a cryovolcanic eruptions  — or plumes of water — spewing from the icy moon.

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Europe’s Mission to Jupiter’s Moons Just Got its First Instrument

Southwest Research Institute’s Norm Pelletier prepares the Ultraviolet Spectrograph (UVS) for delivery and integration onto the European Space Agency’s JUICE spacecraft. As part of a 10-instrument payload to study Jupiter and its large moons, UVS will measure ultraviolet spectra that scientists will use to study the composition and structure of the atmospheres of these bodies and how they interact with Jupiter’s massive magnetosphere. Credit: SwRI

The space agencies of the world have some truly ambitious plans in mind for the coming decade. Alongside missions that will search for evidence for past (and maybe present) life on Mars, next-generation space telescopes, and the “return to the Moon”, there are missions will which will explore Jupiter’s moons for signs of extra-terrestrial life. These include the ESA’s JUpiter Icy Moon Explorer (JUICE), which will launch in 2022.

As part of the agency’s Cosmic Vision 2015-2025 program, this spacecraft will conduct detailed observations of Jupiter and three of its large moons – Ganymede, Callisto, and Europa – to see if they could indeed harbor life in their interiors. Late last month (Feb. 25th), the first instrument that will fly aboard JUICE and aid in these efforts was delivered and began the process of integration with the spacecraft.

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