In the media, there is a habit of throwing a party every time a space probe discovers water. It is amazing how many times water has been discovered Marte On the moon or on any asteroid. This is so surprising that, interpreting those headlines, we can draw two clear conclusions. One: We have limited memory. And two: water is rare in our universe and its mere existence is already news. Also, while the first point is true, the second is counter-intuitive. Water is not only rare but common. It is a molecule Two hydrogen atoms and one oxygen atom The first and third most frequent elements in the universe, respectively.
We can understand the surprise if we at least move from theoretical assumption to practical confirmation. As much as we can estimate the abundance of water in the universe, we did not discover it until that moment, but it happened a long time ago. Without going further, we know that most comets are mostly composed of water ice. Their bodies melt as they approach the Sun, leaving behind two characteristic tails as they shrink in size. We know that other small bodies in our solar system (meteorites and asteroids) are common. Aqua In fact, there is a hypothesis that proposes that our planet's water may have come from them.
So, if water is so common, how do we begin to place so much importance on its discovery in the cosmos? Well, we don't know for sure, but it could be due to a misunderstanding. As many experts have said, it's strange to find out Liquid water Outside of Earth in our solar system. That word itself is important, because although matter exists and is abundant, conditions generally do not allow it to be in a liquid state. The low pressure of space contributes to the gaseous state, and in some nebulae, new stars form. Also, when the pressure increases, for example, on the surface of a planet, the prevailing low temperature of the universe, freezing Aqua Subsurface ice sheets, polar caps, or ice sheets capable of covering the entire Moon directly.
In fact, this is one of the key points to be addressed when we look for life beyond Earth. We don't know what he looks like or how he's supposed to live, but we have reason to think so Liquid water It is very important, so experts consider focusing the search where it exists. In addition to the fact that all life as we know it depends on water, we also know that it is one of the best organic solvents there is, and therefore facilitates the complex chemical reactions necessary for life to take place. Besides being useful as we said, it's abundant, so it doesn't seem crazy that other species need water too. However, we can find examples of liquid water in our surroundings.
Mars is a withered planet, or at least that's what it seems if we let ourselves be carried away by its history. It once resembled the primordial Earth. It had its own atmosphere and oceans of liquid water, and its crust was active, creating and destroying orogenies. Now, there is no more movement beneath its red regolith, its atmosphere has escaped into space and its oceans have dried up. However, water ice remains buried in the Martian soil. Known as permafrost, it does not melt year-round. Also, on the surface, you can see caps filled with snow, the surface of which changes depending on the season of the year. All of this we know for sure, but there's a lot more, and there's an amazing assumption that we can't confirm yet.
Some studies suggest that some lakes of liquid water may disappear into the Martian subsurface. Shallow, but very comprehensive. Places shielded from radiation were when the surface still had an atmosphere. Areas of liquid water where the biochemistry of certain alien microorganisms can be maintained. However, there is a trick. Because how is it possible for these lakes to be liquid on a planet with temperatures ranging from 20ºC to -135ºC. These lakes seem to have a very high concentration of mineral salts. Something similar happens to roads when they fill them with salt, lowering the freezing point of the water there and preventing it from freezing every time the temperature drops.
But if we're looking for a clear example of liquid water in our solar system, we have to travel a little further. Especially, for Jupiter's moons. There we will find Europa, a very special satellite that is slightly smaller than our moon and orbits Jupiter every three and a half days. Beneath its icy crust are oceans of liquid water that, if the calculations are correct, are equal to those of two planets like ours. With these data, Europe shows itself as the most promising candidate, but there is still more.
Two new studies have confirmed the presence of carbon dioxide on Europa's surface, which is commonly associated with biological processes, and found that this carbon, in some way, comes from the oceans beneath the moon's icy shell. Before we ring the bell, it's worth remembering that this carbon dioxide can take many forms and not all of them indicate the presence of life. Perhaps it is a purely passive process, more geological than biological. However, it's another detail that reinforces Europa's image as a prime candidate for finding extraterrestrial life.
As in Europe there are others. Enceladus, for example, a moon of Saturn, spews liquid water from gaps in its south pole. There are many examples, and the more we explore the universe outside the solar system, the more we will discover. Oceanic planets may await us there, where there is hardly any exposed land and whose surface appears to be a vast and continuous body of water. We're not dreaming and I hope it doesn't take long to find out. We increasingly have better telescopes and more precise methods for determining the chemical composition of very distant objects.
But we have to control our excitement because one thing is that we can find water in other worlds, but another strange thing is that we can find life in it. It will require more sophisticated technology. And to fully satisfy our curiosity and drive to find cosmic companions, we need to reach those distant places through expeditions that, now, are so far beyond our technology that we can only consider them as daydreams. So the smartest thing to do is to continue to marvel at every water molecule we find on some wet alien surface.
I do not know:
- Although Europa is outside our star's habitable zone (meaning it doesn't receive enough solar energy to support liquid water), the gravitational pull of massive, nearby Jupiter warms the moon's interior through a process called “tidal warming.” The proximity of two such massive bodies causes them to deform, as if pulled in opposite directions. We can compare it to an elastic band that we pull. As the skin returns to its original length, if we bring the skin close to the rubber, we will notice that it is hot. This is not the same as what happens in Europe, but it allows us to get a rough idea of ​​how it works. Therefore, heat is emitted from the Moon's interior, radiates outward and dissipates in the waters of its oceans.
Notes (MLA):
- Samantha K. Trumbo et al. “Distribution of CO2 in Europe indicates internal source of carbon”. Science, 2023 https://www.science.org/doi/10.1126/science.adg4155
- GL Villanueva et al. “Undetected Endogenous CO2 Ice Composition and Plume Activity at Europa's Surface”. Science, 2023 https://www.science.org/doi/10.1126/science.
