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In October of last year, 2024, the American Aerospace Administration (NASA) sent Europa Clipper probe towards Jupiter. This mission was another attempt to find an answer to a question that humanity has been asking for many hundreds of years: are we alone in the universe?
Although Europa Clipper has already set off to conquer the vast expanses of our solar system, we will have to wait another five years for its arrival at its destination. And although the probe itself will provide some answers to important questions, it is not intended to directly search for life. But first things first.
What's all the fuss about?
It all started with the Galileo spacecraft, which studied Jupiter’s moons from 1995 to 2003. In 1997, it flew past Europa, one of the planet’s four “Galilean” moons, at an altitude of about 200 kilometers. The probe then recorded a strange change in the surrounding plasma and magnetic field.
At the time, scientists couldn't figure out what it was, so they put the mystery on the back burner. However, in 2012, the Hubble Space Telescope was able to see an ultraviolet glow over Europa that was interpreted as water vapor being released into the atmosphere. Further observations confirmed this hypothesis, prompting researchers to take a closer look at the anomaly that Galileo had recorded.
It turned out that The probe not only saw water vapor, but flew through the geyser's exhaust! Thus, in 2018, that is, 21 years later, the secret was revealed, but even more questions arose.
It is worth noting that suspicions about the presence of water on Europa have existed since the 70s. However, thanks to the Galileo data, scientists were able to assess the deformation of Europa under the influence of Jupiter and confirm their ideas. The process here resembles the Earth's ebb and flow - due to gravity, water moves in one direction of Europa and leaves in the other, which causes its shape to change slightly. If this moon consisted of solid material, these fluctuations would be insignificant, but this is not the case.
Not a united Europe?
Jupiter has four major moons (the Galilean moons)—Io, Europa, Ganymede, and Callisto. In total, there are 95 natural objects orbiting the planet.
Io is considered the most volcanically active moon in the entire solar system, so its surface is too hot and unpredictable to support liquid water on the surface.
Others, thanks to the gravitational influence and tidal forces of Jupiter, are constantly in the process of compression and expansion, which generates internal heat and allows water to be maintained in a liquid state. But. Callisto, although it may have an ocean somewhere under an ice cap 300 kilometers thick, is considered geologically “dead”. Therefore, it is unlikely that it would have the energy to give rise to life.
Ganymede, the largest moon in the solar system (it's even bigger than the planet Mercury), may also have a liquid ocean, but to find it we would have to drill to a depth of 150 kilometers. In addition, the presence of its own magnetic field makes it difficult to interpret the data obtained.
So that leaves Europe. It is believed that the thickness of the ice on it is from 15 to 25 kilometers, and the absence of large craters suggests that the exchange of material between the surface and the ocean is constant. At the same time, the geysers mentioned above give humanity the opportunity to look into the interior of Jupiter's moon without the need for deep drilling.
At the very least, NASA hopes that Europa Clipper will be able to replicate Galileo's success, but with the ability to use more advanced and specialized instruments to analyze particles. If flying through a geyser doesn't work, there are alternative ideas that include creating a Europa Lander to descend to the surface, a thermal drill, and even robots capable of reaching Europa's hidden world. However, these are plans for the next stages of the mission in the distant future.
So what are we looking for?
The main task of the current mission is not so much the search for life, but the search for conditions for its occurrenceWe already know that Europa has carbon compounds (including methane), and even oxides. That is We already know about at least the two most important elements for the origin of life on Earth—carbon and oxygen.
However, it is important to understand that even if the probe flies through a cloud of vapor, in which local organisms are purely hypothetically located, it will not be able to recognize them. Europa Clipper has already become the largest automated interplanetary station ever launched by NASA, and one of the most expensive missions in history. It carries a large amount of equipment on board for chemical, geological and thermal analysis of Europa, and the presence of additional instruments would make it even larger, heavier and more expensive.
However, it has equipment on board to search for biomarkers. That is, for example, it can find some complex carbon-based compound that could not have arisen during inorganic synthesis. Or it may notice a high ratio of the isotope carbon-12 to the isotope carbon-13, which on Earth is associated with biological activity.
Although their discovery would be a real sensation, we will only have to definitively confirm or deny the presence of life on Europa during subsequent missions.
And what will we find?
As mentioned above, Europa Clipper will likely be followed by other spacecraft to refine the data and analyze new parameters. All of this could take decades and require multi-billion dollar financial investments.
However, let's "play around" a bit and fantasize about what the Europa Clipper and all subsequent missions might end up being.
Important: The text below should be taken solely as speculation without any justification.
The result of the study of Europe can be formulated in four main options and sorted in order of decreasing probability.
Option 1. Need more missions
The most likely option that comes to mind is that we won't find life there, but "it's not that clear-cut." There are several reasons for this.
If scientists say "there is no one in the room," it means they looked into every corner and under every baseboard to make sure. If you scale the conventional "room" to an object the size of Europe, things become much more complicated. The surface area of Jupiter's moon is over 30 million square kilometers. For comparison, the area of Ukraine is only 603,6 thousand square kilometers, that is, about 50 times smaller.
The depth of the ocean beneath Europa's ice is estimated to be between 60 and 150 km. For comparison, the Mariana Trench, the deepest place on Earth, is only 11 km deep.
Considering that over the entire time humans have explored the Earth's oceans, learned them by 5-10%, then it will take more than one hundred years to reveal all the secrets of even our home planet. The volume of liquid water in Europa, according to current estimates, is 2-3 times greater than the volume of all Earth's oceans. In general, in the near future, scientists will definitely have something to do, and maybe their children and grandchildren will have something to do too.
Option 2: There is nothing there
For the reasons stated above, we consider this option less likely.
However, if Europa Clipper or future missions show that the water in Europa's ocean is too toxic or radioactive for anything to survive there, even in theory, then we could then look elsewhere for extraterrestrial life.
Fortunately, the Universe is huge and there are enough places where life can hide from us even without Europe.
Option 3: Life?
Well, we already know that carbon exists on Europa. However, even on Earth, carbon-based compounds can appear in processes that are in no way related to life, so we shouldn't get excited ahead of time.
However, even if scientists hos and if they are found on Jupiter's moons, it will only raise new questions like "Is this even life?"
It would be nice to go down to our home planet to see what the problem is. School biology textbooks say that life can be defined by seven characteristics:
- growth and development;
- energy consumption to fuel internal processes (metabolism);
- ability to reproduce;
- inheritance of parental traits by offspring;
- cellular structure;
- internal stability (homeostasis);
- reaction to external stimuli.
The presence of these signs is recorded in all living things on Earth — from plants and animals to the smallest bacteria.
However, viruses, although they are made up of the same “building blocks” as living organisms, do not meet all the conditions on the list. Because of this, the question of whether they should be considered life has given rise to numerous heated discussions in the scientific community, and arguments for and against are still being expressed to this day. And when it comes to the classification of smaller “things” like viroids (plant pathogens consisting only of a chain of RNA), things only get weirder.
The most obvious question that arises in the context of the search for life on Europa is: should the local organisms fit into the terrestrial classification? Let it remain open.
But if the stars in the sky align and NASA finds something that meets all seven signs of life, it will most likely be some kind of prokaryotic organism resembling terrestrial archaea — single-celled creatures without a nucleus and organelles, similar to bacteria, but with an even simpler structure.
The archaea variant was chosen because on Earth they are often live in extreme conditions, including in hydrothermal vents, in Arctic ice, and even in active volcanoes. That is, they are a good example of how living organisms can exist even in unsuitable conditions.
Life on our planet is thought to have originated in the warm, mineral-rich walls of “black smokers”—deep-sea thermal vents. And if Jupiter’s moon has something similar, scientists will be able to focus their search for “aliens” on a specific spot, instead of searching for them across the entire ocean.
Option 4: What if…
The idea of finding multicellular life on Europa excites the minds of space enthusiasts around the world, but too many coincidences would have to occur for it not only to appear, but also to survive.
Even if we delve deeper into the history of our planet, we can find that at the initial stage of its development, several events occurred that almost wiped out early life.
An example is the "Gardens of Ediacaran", in which some of the first multicellular creatures developed. A short retelling of this story: they failed, and our distant ancestors appeared millions of years later. Therefore, on Europe, the probability that multicellular organisms have not yet appeared or have already died out is much higher than that they are living right now.
For our planet, one of the main milestones in the development of life was the emergence of photosynthesis. All life requires energy, and sunlight is essentially an unlimited source of it. However, in the ocean of Europa, hidden under a thick layer of ice, such a luxury will not be, and therefore local organisms will have to obtain energy from chemical reactions, the source of which is tectonic processes. This limitation in resources will be a huge problem for multicellular life, if it tries to appear in such conditions.
If multicellular aliens do exist, their appearance may be completely unbelievable. However, for inspiration, we can look at the invertebrates of Earth's oceans, which can amaze with the diversity of forms and survival strategies.
What we can say for sure is that we won't find little green men in Europa's ocean. No. Sorry. Just no.
