Astronomers certainly dream of the day when humans will be capable of traveling long distances in interstellar travels around the galaxies and finding new ways of life that will bring new ways to conceive the reality. But, unfortunately, until now it has been just a dream, limited by our relative “rudimentary” technology that keeps us on the borders of our beautiful planet. Nevertheless, more and more work has been done in recent years to take, at least, the first glance in our neighborhood to start testing our understanding of life.
The planet Mars is the object of special attention. The results provided by the Martian missions Mariner 9, Viking 1 and 2, Mars Pathfinder, Mars Global Surveyor, Mars Odyssey, Mars Express, the two Mars Exploration rovers Spirit and Opportunity, and the Phoenix spacecraft clearly indicate that Mars hosted large amounts of water on its surface.
The permanent presence of water assumes a temperature constantly near or above 0 C, a temperature probably reached thanks to the existence of a dense atmosphere generating a significant youporn greenhouse effect. Thanks to this atmosphere, the planet was able to accumulate micrometeorites on its surface like the Earth. The ingredients that allowed life to appear on Earth were therefore gathered on Mars. It is therefore tempting to think that an elementary life of terrestrial type could have appeared and developed on the red planet.
Viking experiments did not find organic molecules on the surface of Mars, but some SNC meteorites (after the three classes of Shergotty, Nakhla, and Chassigny meteorites) contain organic molecules. These meteorites, now numbering 50, most likely find their origin on Mars. Among them is the famous meteorite ALH 84001 presented as containing fossilized Martian nanobacteria. This interpretation is now abandoned.
The Martian oceans deposited sediment, observed by the cameras of Mars Global Surveyor and Mars Express and by the Opportunity rover. Sedimentary Martian meteorites would represent privileged materials for the search for biological signatures. However, to date, we have no sedimentary meteorites. Are they destroyed upon entry into the atmosphere? To verify this point, experiments with artificial meteorites were piloted by the exobiology team of the Center for Molecular Biophysics, in collaboration with teams from Austria, the UK, the Netherlands, and Switzerland.
A dolomite, calcium magnesium carbonate, set in the heat shield of a Russian FOTON πορνο automatic satellite has been recovered up to 30%, demonstrating that extraterrestrial sediments can survive the atmospheric impact.
Other sedimentary rocks have been inoculated with a photosynthetic cyanobacterium living within 5 millimeters of the rock surface. Despite extensive thermal ablation, all the rocks partially survived entry into the atmosphere. However, no microorganism survived. The death of the photosynthetic cyanobacteria is a clear indication that terrestrial photosynthesis was created in place and could not be imported from space via a meteorite. Sedimentary rocks containing fossilized microorganisms have also survived.
The Mars Express Planetary Fourier Spectrometer has detected methane in the atmosphere of Mars. The content varies between 10 and 30 parts per billion. The presence of methane has been confirmed from Earth. With a lifespan of 300 years, a permanent source of methane is needed: biological? geological? To decide, it would be necessary to be able to detect other gaseous biomarkers (ammonia, formaldehyde) but these compounds have a very short lifespan, of the order of a few hours in the Martian environment.
Epicurus dreamed of an infinity of living worlds, a dream taken up later by great thinkers such as Giordano Bruno, Bernard Le Bovier de Fontenelle, Christiaan Huygens, and Emmanuel Kant. To this day, this dream has not yet received concrete reality. However, we are increasingly aware of the conditions that allowed life to emerge on Earth, and the extraterrestrial sites where these conditions prevail are increasingly identified. But why this relentlessness in seeking extraterrestrial life? Einstein answered by writing: Wichtig ist, dass man nicht aufhört zu fragen (It is important to never stop asking).
It is indeed curiosity and the urge to understand that has brought humans to present knowledge. Beyond the urgent need to understand, this research has concretely demonstrated the primordial role of terrestrial water, an essential partner of life, and the fragility of the human species, a tiny entity lost in the vastness of the Universe. No one can predict what the societal needs of tomorrow will be, and great scientific advances often happen by accident, the paths of discovery being impenetrable. Sacrificing exploratory research, known as knowledge, on the altar of short-term productivity would seriously hamper the future of our society.
When we wonder about life elsewhere in the Universe, we must above all analyze the conditions favorable to the appearance of life in its most primitive forms, that is to say, the transition from chemistry to biology or even transition from molecular to single-cell forms. Liquid water is obviously a very favorable factor, and in the face of the extraordinary multitude of planetary systems present in our Galaxy, one can rightly think that life could have appeared elsewhere in many places.
Here we will ask ourselves the following question: if life has appeared elsewhere, will it evolve into more complex forms or even civilizations as it has happened on Earth?
To better understand this question, we must recognize the importance of time. It does indeed play a central role. To do this, let’s transpose the age of the Universe from 13.7 billion years to a single year of what we will call the Cosmic Calendar. Briefly in this Cosmic Calendar, the Solar System appears on September 13, life on Earth is already there at the end of September while multicellular life forms do not appear until mid-December. Homo sapiens sapiens is only present on December 31 a few minutes before midnight!
As in the last chapter of the book “Where are we going to live tomorrow” (A. Vidal-Madjar, 2009), let us try to imagine the future of humanity, not in 10 years or even in 100 or 1000 years, but really in 20,000 years. This is only one minute after midnight on the Cosmic Calendar! And yet in this “tiny” period, it is certain that mankind will have already settled on all the planets of the Solar System and will undoubtedly have started a few first attempts to reach the stars.
If even a million years were necessary to reach them, that is to say not even an hour after midnight on the Cosmic Calendar, it is easy to demonstrate that then a few tens of millions of additional years should be sufficient to humanity to explore all the planets of our Galaxy, that is to say before January 2 of the New Cosmic Year!
If therefore a single civilization had crossed only once what we have lived on Earth, with a single Cosmic day in advance (for example by having appeared on a planetary system on Cosmic September 12), this civilization would already be everywhere in the Galaxy and especially right here on Earth. As is not obvious, Enrico Fermi as early as the 1950s felt compelled to cry out: “Where are they? “. This famous question has since then been widely debated under the name of the Fermi Paradox.
This argument is true if every implicit step in this reasoning turns out to be correct. The assumptions made are as follows:
If these four steps are true, then the Fermi Paradox takes on its full significance. If, on the other hand, only one of these steps does not occur, there is nothing paradoxical about the Fermi Paradox!
The discussion of the paradox can be conducted as follows:
Let us, therefore, analyze this fourth point: once present on a planet, does a civilization become capable of crossing interstellar spaces or not?
This is a major clue about how life started in the universe pic.twitter.com/YYKTSIguuX
— Seeker (@Seeker) September 1, 2020
4a) Few civilizations emerge, a few dozen for example. We would therefore be very few and this hypothesis would then strongly resemble the one which claims that we are alone in the Universe because differentiating between 1 and a few dozen is of course impossible in the highly speculative and very difficult context of this discussion. This first hypothesis, therefore, amounts to saying that we are “almost alone” in the Universe.
4b) A very large number of new civilizations are continually being born in the Galaxy, civilizations which would then number in the thousands, even millions, not to say billions!
As we discover once again if we ask ourselves the question of whether we are alone in the Universe as a civilization, we only must discuss the last hypothesis 4b). In all other cases, the answer would be very clear: We are alone in the Universe!
The only way out, therefore, is that hypothesis 4b) is correct. There would then be very many extraterrestrial civilizations currently present in the Galaxy.
In the latter case, they are indeed everywhere around us, but something must necessarily prevent them ALL, systematically, from traveling in interstellar spaces, otherwise they would of course already be here. We see then the interest of having separated the discussion between cases 4a) and 4b) because now we must find a “universal” explanation which is capable of preventing ALL civilizations, which in this case are millions, from traveling to ours.
What are the possible mechanisms to explain our isolation in our little corner of the Universe?
Many have been proposed. The first most obvious reason is: interstellar travel is simply impossible.
This reason would certainly be major and has been widely debated by many authors. It would seem, however, that interstellar travel is certainly a difficult exercise but not insurmountable at least for automatic probes. We must look elsewhere. Other reasons often cited as to why the “others” are not already there are:
All these socio-psychological reasons come up against the same difficulty in the context of hypothesis 4b) which assumes that the number of civilizations is considerable. Indeed if it is always possible to say that such and such a civilization destroyed itself, or simply did not want to make these interstellar jumps, or any other reason of this type, it is not possible to think that ALL of the myriads of them fall into these different obstacles SYSTEMATICALLY. Indeed, it only takes one and only one of them to avoid all these obstacles for them to already be here! Since they do not appear to be here, hypothesis 4b) is false.
There cannot be a very large number of civilizations currently in the Galaxy, this number is necessarily very small, and it is even quite possible that it is equal to 1!
As you can see, whatever the hypothesis you choose, we come to the same conclusion: We are alone!
For those die-hards of the existence of “others” elsewhere, there remains a little hope, which is 4a), that is, we are not alone but relatively few. It is with this glimmer of hope that the researchers of the SETI program attach themselves to this idea because if there are only 2 of us in the Galaxy right now, it would be extraordinary to make a successful contact.
The answer to the question “Where are they?” seems firmly established: Nowhere or almost nowhere!
Or: Here on Earth!