What is stopping us from landing on Europa?
Remember 2010: The Year We Make Contact, the sequel to 2001: A Space Odyssey? In the film,
nine years after the Discovery's disaster, Heywood Floyd, the scientist we already
met in "2001," embarks on the Leonov, a Russian spacecraft, for a joint expedition following the
footsteps of the ill-fated Jupiter mission. Arriving in orbit around the giant planet,
the Leonov discovers traces of life on Europa, a moon of Jupiter. More importantly, it locates
the missing spacecraft. The rebellious onboard computer HAL is reactivated, not without concern,
by its original programmer. Dave Bowman, now an ethereal being capable of traveling through space,
visits Floyd and predicts that something wonderful will soon happen on Jupiter.
And indeed, something does happen. The monolith that orbited Jupiter in "2001" descends onto
the planet, creates millions of copies of itself, and increases Jupiter's mass, triggering a chain
reaction that transforms it into a new star. Why does the monolith perform this miracle?
The message Bowman dictates to Earth explains: "All these worlds..." he says,
referring to the former moons of Jupiter made habitable by the new star's warmth, "...are yours.
Except Europa. Do not attempt to land on Europa." From here, it becomes clear that the mysterious
aliens, the creators of the monolith, wanted to give a chance to the creatures of Europa,
aiding their evolution as they did millennia ago with mankind's ancestors.
You'll admit it's not easy to escape the suggestion of
that "do not attempt to land on Europa." And wouldn't you know it, what could only
appear as a narrative cue in the film's plot became a reality a few years later:
official science recognized Europa as the most suitable world to harbor primitive forms of life.
Coincidence, or is there something more to it? Yes, there's an ocean beneath it all!
Europa boasts a secret hidden beneath its icy surface: an ocean of liquid water with
the potential to unveil the mysteries of extraterrestrial life and reshape
our understanding of the universe. Unfortunately, NASA made a grave
mistake. At the end of this extraordinary and "chilling" video, we'll tell you what it is.
A point of light. That's what Europa has been for almost four centuries: a tiny source of light,
dim as a sixth-magnitude star. Nothing more than the second moon in distance
from Jupiter, and the smallest of the four discovered by Galileo in January 1610.
By the end of the 19th century, its diameter was estimated to be around 3100 km, comparable
to our Moon. It was thus reasonable to think of it as a body very similar, dry, and heavily
cratered. It was only in the '60s, thanks to the first spectroscopic studies, that suspicions
arose about its surface being covered in ice. Then the final word came from interplanetary
probes and the first missions to the outer planets It was Voyager 1, in March 1979, that first
captured close-up images of Jupiter's Galilean moons, particularly Io, Ganymede, and Callisto.
Europa, slightly more distant during the flyby, had to wait for Voyager 2's arrival in July 1979.
The initial high-resolution images revealed ice plains crossed by thousands of dark streaks
forming a gigantic reddish network across the entire surface. Filamentous structures
were interspersed with vast plains disturbed by chaotic terrains and dark
regions scattered with brownish-red material. It was later revealed that these streaks are,
in fact, grooves up to 20 km wide, a result of the breaking and reformation of the icy crust,
continually disrupted by the variable tidal forces induced by Jupiter.
These fractures traverse the surface for hundreds of kilometers, with the
peculiarity of branching or splitting, creating complex and irregular patterns.
Some are wide and deep, while others are thin and superficial, with the most recent ones overlying
the older ones. If the fractures are ancient, meaning they have opened and closed many times,
they form reliefs along their edges throughout their length, similar to the oceanic ridges on
Earth when two tectonic plates come into conflict. Then there are bright or dark regions that stand
out from the rest of the surface, which typically has a white-yellowish color.
They result from variations in the chemical composition or temperature of the ice. Some
are large and round, others are small and irregular; single or multiple and overlapping.
From the start, the probes revealed something even more extraordinary:
the almost complete absence of impact craters. There were some, but not as many as one would
expect from a planet with little to no atmosphere. Someone took the time to
count them, and it seems there are only 3500 with a diameter greater than 1 km.
At that point, three crucial questions emerged (at least): 1) Why are there so few
impact craters visible? 2) Why is the surface cracking in this way? 3) What is leaking from
the planet's interior? Needless to say, all three questions had to be resolved together.
Since it is scientifically unreasonable to believe that Europa has few impact craters only by chance,
there was only one other hypothesis that could explain the phenomenon.
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Namely, that the planetary surface had been "reshaped" over time by particular
geological events. In other words, the moon had to be geologically active, meaning there
must be a permanent heat source inside Europa. The first clues in favor of this hypothesis came
from considering the so-called "Laplace resonance," a specific gravitational
interaction phenomenon between Jupiter, Io, Europa, and Ganymede.
In practice, the revolution periods of these moons are integer multiples of each
other. This means that every time Ganymede completes an orbit around Jupiter, Europa
completes two orbits, and Io completes four. This specific way of orbiting Jupiter causes
gravitational perturbations that, periodically "stretching" the moon in all directions,
result in tidal effects producing heat and significant mechanical effects.
This, for example, is the same cause of Io's intense volcanic activity,
but it has been calculated that Europa's interior could also be warm enough to melt the ice beneath
the surface at depths exceeding 10 km. That's how, although it might have seemed
like a bizarre idea, astronomers seriously began to consider that beneath Europa's icy crust,
there might indeed hide a vast liquid ocean. The Galileo probe confirmed this notion.
Starting from December 1995, it had flown by Europa about a dozen times,
capturing thousands of extraordinary photos. More importantly, it measured gravity values
just below the icy cover compatible with a density similar to that of water. Salty water,
to be precise… a real ocean, about a hundred kilometers deep, with a volume at least
twice that of all Earth's oceans combined. The evidence for some form of water or slush
beneath Europa's surface is quite strong, based on models of how a buried ocean would
influence the ice above it. Measurements of the Moon's magnetic field also suggested the
presence of an electrically conductive fluid beneath the surface, such as salty water.
Later on, what initially appeared as a peculiarity of Europa - the presence of
an ocean beneath its surface - was also found on Ganymede, the largest moon in the Solar System,
and on Enceladus, Saturn's moon. At the time of the discovery,
the exceptional nature of this phenomenon prompted NASA and ESA to plan exploratory missions to reach
the moon's surface, making it one of the hottest targets in the solar system exploration program.
This interest was driven not only by the concrete hypothesis of the underwater ocean
but also by the possibility that Europa could have an environment similar to
hydrothermal vents found on Earth's ocean floor. More accurate observations in 2013 by the Hubble
Space Telescope allowed the identification of water vapor geysers, similar to those previously
found on Enceladus. This strengthened the hypothesis of a warm ocean and, more importantly,
the possibility of hydrothermal microbial life. Geysers are columns of water vapor that form
when liquid water from the underlying ocean escapes through cracks in Europa's crust.
They result from pressure and temperature causing vaporization or sublimation of water.
Some geysers are tall and powerful, while others are shorter and weaker. Some geysers are constant,
while others are intermittent or seasonal. The necessary heat for increasing water
pressure underground and forming the geyser mainly comes from the tidal forces generated
by Jupiter. These forces can deform the rocky core, causing friction that releases heat.
This heat transfers to the subsurface ocean, which, in turn, warms the icy crust. In certain
locations, liquid water manages to escape through cracks in the crust, forming water vapor geysers.
The interest in these phenomena lies in the fact that geysers could bring materials from
the ocean to the surface. Spectroscopic analysis conducted by probes demonstrated
that the long reddish streaks on the surface could be interpreted as deposits of magnesium sulfate,
essentially the salt residue of water brought to the surface by the geysers… a
perfect substrate for organic molecules. Indeed, these features made Europa one
of the most intriguing places in the search for chemosynthetic microbial life. However,
over the years, partly due to the discovery of other worlds with similar oceans and partly due
to the economic crisis reducing space agency budgets, interest in Europa has waned, and most
probe exploration projects have been abandoned. The only remaining, recently confirmed mission
is the launch by 2025 of a NASA mission called Europa Clipper.
It consists of a spacecraft orbiting Jupiter, allowing it to make 44 close
flybys of Europa. Europa Clipper is expected to reach Jupiter by the end of this decade,
potentially followed and assisted by the ESA's Jupiter Icy Moons Explorer mission. The latter
will fly by Europa twice and Callisto multiple times before entering orbit around Ganymede.
From this joint mission, scientists expect confirmations and assessments
regarding habitability and the potential for future human settlement on Europa's surface.
However, designing a mission for the colonization of a remote celestial body is obviously much more
complex than sending an interplanetary probe. While permanent bases on the Moon and Mars may
reasonably be expected within the next decade, the colonization of Europa is projected to take
at least a hundred years - unless, of course, one of the upcoming probes confirms the presence
of life, even at the microbial level. In that case, sending a manned mission
to Europa would likely become an immediate priority, potentially halving the timeline.
Everything depends on the motivations of that particular historical moment.
The question at this point is: Does NASA truly intend to find signs of life on Europa
or on any other object in the solar system? Most of you would undoubtedly answer yes.
But then, why does NASA operate, plan, and act as if its primary goal were different?
This has been observed with numerous missions sent to Mars, primarily capturing beautiful
photographs while almost meticulously avoiding sending rovers capable of chemical analyses for
life detection - a trend that we've seen since the Viking missions in 1971, over half a century ago!
The same attitude persists with Europa. What's the point of sending an orbiter instead of a
surface rover? NASA, once again, emphasizes that "the Europa Clipper mission does not
have the direct goal of searching for life but rather studying the habitability conditions of
Europa. The Europa Clipper cannot confirm or deny the presence of life on Europa, but it
can provide valuable information to understand if life could exist or have evolved on that moon."
This echoes the same refrain sung for Martian missions... Remember?
Meanwhile, we have gained certainty that water from Europa's ocean reaches the surface,
sprayed by geysers up to tens of kilometers high. So why not send a rover capable of analyzing the
material that would have accumulated over thousands of years near the geyser vent?
For some reason, NASA seems uninterested in this prospect.
Perhaps for them, maintaining a steady flow of government funding is more crucial than providing
a definitive answer to the most significant scientific question of the millennium.
Unfortunately, this leads us to fear that NASA might already know that life does not exist in the
solar system beyond Earth. They may be aware that revealing this would likely turn public opinion
against further financial allocations. Is this a conspiracy theory? Perhaps...
At least NASA is not taking Dave Bowman's warning literally…
We'd love to hear your opinion on the matter!