Sunday02 February 2025
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Aliens might be closer than we think: what secrets does Jupiter's moon hold, and why is this a matter of great significance?

The mission has already become one of the most expensive in NASA's history.
Инопланетяне могут быть ближе, чем мы думаем: что таит в себе луна Юпитера и почему это важно для науки.

In October of 2024, the American aerospace agency (NASA) launched the Europa Clipper probe towards Jupiter. This mission represents yet another effort to find an answer to a question that humanity has pondered for centuries: are we alone in the universe?

Although the Europa Clipper has already embarked on its journey through the vast expanses of our Solar System, we will have to wait another five years for its arrival at its destination. While the probe will provide some answers to important questions, it is not designed for the search for life itself. However, let's take it step by step.

What’s all the fuss about?

It all began with the "Galileo" spacecraft, which studied Jupiter's moons from 1995 to 2003. In 1997, it flew past Europa—one of the four "Galilean" moons named after the great astronomer who discovered them—at an altitude of about 200 kilometers. At that time, it recorded strange changes in the surrounding plasma and magnetic field.

Back then, scientists couldn't figure out what it was, so they shelved the mystery for later. However, in 2012, the Hubble Space Telescope was able to observe ultraviolet light above Europa, which was interpreted as a plume of water vapor in the atmosphere. Further observations confirmed this hypothesis, prompting researchers to take a closer look at the anomaly recorded by Galileo.

It turned out that the probe not only detected water vapor but flew through a geyser's plume! Thus, in 2018—21 years later—the mystery was unveiled, but even more questions arose.

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It is worth noting that suspicions about the presence of water on Europa have existed since the 1970s. However, thanks to data from Galileo, scientists were able to assess Europa's deformation under Jupiter's influence and validate their ideas. The process here is similar to Earth's tides—due to gravity, water moves to one side of Europa and recedes from the other, causing its shape to change slightly. If this moon were made of solid material, these fluctuations would be insignificant.

Not just Europa?

Jupiter has four main moons (the same Galilean satellites)—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, making its surface too hot and unpredictable to support liquid water.

The others, due to gravitational influences and tidal forces from Jupiter, are constantly undergoing compression and stretching, generating internal heat that allows water to remain in liquid form. However, while Callisto may have an ocean beneath its 300-kilometer-thick ice cap, it is considered geologically "dead." Therefore, it is unlikely to have the energy to initiate life.

Ganymede, being the largest moon in the Solar System (even larger than the planet Mercury), may also have a liquid ocean, but detecting it would require drilling to a depth of 150 kilometers. Furthermore, the presence of its own magnetic field complicates the interpretation of the data obtained.

Thus, Europa remains the focus. It is believed that the thickness of the ice on it ranges from 15 to 25 kilometers, and the absence of large craters indicates that material exchange between the surface and the ocean is ongoing. Moreover, the geysers mentioned earlier provide humanity with a chance to glimpse the depths of Jupiter's moon without the need for deep drilling.

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At least, NASA hopes that Europa Clipper can replicate Galileo's success, but with the ability to use more advanced and specialized instruments for particle analysis. If it fails to fly through the geyser, alternative ideas exist, including the creation of a lander called Europa Lander, a thermal drill, and even robots capable of reaching Europa's hidden world. However, these are plans for future stages of the mission.

So what are we searching for?

The main objective of the current mission is not so much the search for life but rather the search for conditions for its emergence. We already know that Europa has carbon compounds (specifically methane) and oxides. This means that at least two of the most crucial elements for life as we understand it—carbon and oxygen—are already known to us.

However, it is essential to understand that even if the probe flies through a vapor cloud that hypothetically contains local organisms, it will not be able to recognize them. Europa Clipper has already become the largest automated interplanetary station ever launched by NASA, as well as one of the most expensive missions in history. It carries a wealth of equipment for chemical, geological, and thermal analyses of Europa, and adding more instruments would only make it larger, heavier, and more expensive.

Nevertheless, it does have equipment for searching for biomarker indicators. For instance, it might find a complex carbon-based compound that could not have arisen through inorganic synthesis. Or it might detect a high ratio of the carbon-12 isotope to the carbon-13 isotope, which on Earth is associated with biological activity.

While their discovery would be sensational, we will only be able to definitively confirm or deny the presence of life on Europa in future missions.

And what will we find?

As mentioned above, other spacecraft will likely follow Europa Clipper to refine data and analyze new parameters. This could take decades and require multi-billion dollar investments.

However, let's indulge in a bit of "play" and speculate on how Europa Clipper and all subsequent missions might conclude.

Important: the text below should be viewed solely as speculation without any grounding.

The outcome of the exploration of Europa can be summarized in four main scenarios, sorted by decreasing probability.

Scenario 1: More missions are needed

The most likely scenario that comes to mind is that we will not find life there, but "it's not that straightforward." There are several reasons for this.

If scientists say "there's no one in the room," it means they have checked every corner and under every baseboard to be absolutely sure. If we scale this hypothetical "room" to an object the size of Europa, the situation becomes much more complicated. The surface area of Jupiter's moon is over 30 million square kilometers. For comparison, the area of Ukraine is only 603,600 square kilometers, which is about 50 times smaller.

The depth of the ocean beneath Europa's ice is estimated to range from 60 to 150 kilometers. In comparison, the depth of the Mariana Trench, the deepest point on Earth, is only 11 kilometers.

If we consider that throughout the study of Earth's oceans, humans have explored only 5-10% of them, it will take centuries to unveil all the secrets of even our home planet. The volume of liquid water on Europa, according to current estimates, is 2-3 times greater than the volume of all Earth's oceans. In short, scientists will certainly have their hands full for the foreseeable future, and perhaps their children and grandchildren will too.

Scenario 2: There’s nothing there

For the reasons stated above, this scenario can be considered 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, even theoretically, then we can move on to search for extraterrestrial life elsewhere.

Fortunately, the universe is vast, and there are plenty of places where life could hide from us without Europa.

Scenario 3: Life?

Well, we already know that there is carbon on Europa. However, even on Earth, carbon-based compounds can arise through processes unrelated to life, so we shouldn't celebrate prematurely.

Even if scientists do find something on Jupiter's moon, it would only raise new questions like "is this life?"

Here, it would be helpful to look back at our home planet to see what the issue is. School biology textbooks state that life can be determined by seven criteria:

  • growth and development;
  • energy consumption to fuel internal processes (metabolism);
  • ability to reproduce;
  • inheritance of parental traits by offspring;
  • cellular structure;
  • internal stability (homeostasis);
  • response to external stimuli.

The presence of these characteristics is observed in all living things on Earth—from plants and animals to the tiniest bacteria.

However, viruses, despite being made of the same "building blocks" as living organisms, do not fulfill all the conditions on the list. Because of this, the question of whether they should be considered life has sparked numerous heated debates within the scientific community, with arguments "for" and "against" still being raised today. Moreover, if we delve into the classification of smaller "entities" like viroids (plant pathogens consisting solely of a chain of RNA), things become even stranger.

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The most obvious question that arises in the context of searching for life on Europa is