00:00The Panspermia theory postulates that life can naturally spread in space,
00:06like seeds scattered throughout the universe.
00:09Long debated, this hypothesis was lacking proof until recently.
00:14Thanks to scientific advances, it is now taken seriously.
00:19It used to be believed that it was impossible for an organism to survive its expulsion from a planet,
00:25and that some micro-organisms managed to cross space and land intact on another star.
00:33In the 1970s, the interest in this question was revived after the discovery of Martian rocks on Earth,
00:40demonstrating that materials could travel between planets.
00:43Scientists have identified several mechanisms allowing rock fragments to be propelled into space
00:50and to resist the rigors of travel.
00:53These observations have given a new credit to the Panspermia hypothesis.
00:57Researchers wondered if micro-organisms could have migrated from one planet to another within the solar system.
01:04To make this conceivable, they would have to survive their expulsion,
01:08withstand the space vacuum, and endure the impact on a new star.
01:12To test this hypothesis, many experiments have been carried out to reproduce these extreme environments.
01:19It turned out that some sports resist these conditions taken individually,
01:24and even to combinations of stress factors in laboratories.
01:27A transfer of micro-organisms between Mars and Earth, or to another habitable planet, therefore seems scientifically plausible.
01:35This phenomenon could not be limited to Mars and Earth.
01:39Some moons of Jupiter and Saturn, such as Kyo, Europe, Ganymede, Callisto, Titan, and Enceladus,
01:46also present conditions likely to allow the survival of biological forms.
01:51Micro-organisms can survive years in space with a simple protection against UV.
01:57In a way, they look like cosmic superheroes, provided they are slightly sheltered.
02:03And if they are under a layer of two meters of meteorite, their longevity could reach 25 million years,
02:09a duration much longer than that of most marriages.
02:14Even more surprising, scientists have managed to revive terrestrial microbes after a sleep of 250 million years.
02:22It's a bit like a fossil suddenly found life and screamed,
02:26Surprise!
02:28All these discoveries have shaken our approach to the search for extraterrestrial life.
02:33In the past, we thought that life could only prosper on planets with similar conditions to those on Earth.
02:39Now, we know that it can adapt to extreme environments.
02:43This better understanding has contributed to the development of astrobiology,
02:47a discipline devoted to the study of the origin, evolution, and distribution of life in the universe.
02:54Mars is among the most promising targets.
02:58We know that it once had an environment similar to that of Earth,
03:02which means that life could have appeared there.
03:06In addition, the presence of traces of methane in its atmosphere intrigues scientists,
03:11because this gas could be of biological origin.
03:14Recently, underground lakes of liquid water have also been detected,
03:19revealing the possibility that Martian microbes are still developing there today.
03:25Europe, one of Jupiter's moons, represents another fascinating track.
03:30Its underground ocean could house a life similar to those that proliferate around the hydrothermal sources of the terrestrial abysses,
03:37or in the Vostok Lake, buried under the Antarctic ice.
03:41Encelade, a moon of Saturn,
03:43has geysers that project water vapor and organic particles,
03:48a possible sign of biological activity.
03:52In short, space is a territory full of mysteries and surprises.
03:57Who knows what discoveries await us yet?
04:01Yes, this long explanation was based on the Panspermi.
04:05But it is certainly not the only theory on the origin of life in space.
04:10In addition to the Panspermi, there is the Directed Panspermi,
04:15a slightly bolder idea.
04:18It suggests that life on Earth would have been intentionally introduced by an advanced extraterrestrial civilization,
04:25assuming that life is too rare in the universe to have spontaneously appeared on our planet.
04:35The Directed Panspermi is based on the idea that beings from other planets would have intentionally sent life to Earth.
04:42I'm not kidding.
04:44Some advances, as well as extraterrestrials, would have deliberately sent microorganisms,
04:49or even entire organisms, to initiate life on our planet.
04:54According to this theory,
04:56these interstellar travelers would have sought to spread life throughout the universe,
05:00and Earth would have been just a step among others.
05:03A bit like cosmic gardening,
05:05they would have sown life and let nature grow.
05:10As strange as it may seem,
05:12some scientists take this hypothesis seriously.
05:16They believe that the complexity of life on Earth is too great to be the result of mere chance,
05:21and that an external influence could have played a role.
05:24However, the classic theory of the Directed Panspermi remains, in my opinion, more convincing.
05:32Another hypothesis, called chemical evolution, proposes a different approach.
05:36It suggests that life would have been born from simple organic molecules,
05:40spontaneously formed in the primitive atmosphere of Earth or in space.
05:46These molecules would then have evolved into more complex structures,
05:50giving birth to the first living organisms.
05:53Primitive Earth presented very different conditions from those we know today.
05:59Its atmosphere was mainly made up of gases such as methane, ammonia and carbon dioxide,
06:05without any trace of oxygen.
06:07These conditions were conducive to the formation of organic molecules.
06:11Among the experiments that supported the theory of chemical evolution,
06:15the Miller-Urey experiment, carried out in 1952, is undoubtedly the most famous.
06:21Stanley Miller and Harold Urey recreated in a laboratory the supposed atmosphere of primitive Earth
06:27and succeeded in producing amino acids, the fundamental components of proteins.
06:33This experiment thus demonstrated that organic molecules
06:37could emerge from simple inorganic compounds in conditions similar to those of the time.
06:44Over time, these elementary organic molecules
06:47came together to form more and more complex structures,
06:50gradually leading to the appearance of the first living organisms.
06:54This process would have taken millions of years,
06:57and probably took place in successive stages.
07:01Although chemical evolution remains a hypothesis
07:03and that many questions remain about the origin of life,
07:07it is a credible explanation of the way in which inanimate matter
07:11could have given birth to living beings.
07:15Ready to discover a new hypothesis?
07:17Let's talk about the theory of hydrothermal sources.
07:20According to this idea, life on Earth would have appeared near the underwater chimneys
07:24located at the bottom of the oceans.
07:27These formations release a mixture of minerals and chemical substances in a heated water,
07:32thus creating an environment that could have favored the emergence of the first organic molecules
07:37and the development of life.
07:39This theory offers another explanation of the origin of life.
07:43It suggests that, in the ocean depths,
07:46sources of heated water fed by the activity of the Earth's core
07:50release a great variety of minerals and chemical compounds.
07:54These particular conditions could have offered an ideal setting
07:57for the appearance of the first forms of life.
08:00Scientists estimate that the first living organisms
08:03could have emerged around these hydrothermal sources,
08:06exploiting the chemical and mineral elements present to produce energy.
08:10Over time, these organisms would have evolved and colonized other areas of the ocean.
08:15Although the theory of hydrothermal sources is still a subject of research and debate,
08:20it is a fascinating clue to understand the origin of life on Earth.
08:25Let's finish with another major hypothesis,
08:27that of the world of AARN.
08:29According to this theory, ribonucleic acid
08:32would have been the first molecule capable of self-replicating.
08:35Playing a key role in the evolution of life.
08:38AARN is indeed capable of storing genetic information
08:42and catalyzing chemical reactions,
08:44which would make it a possible precursor of DNA and proteins.
08:49In other words, this hypothesis suggests that life on Earth
08:52could well have started with a simple molecule of AARN.
08:57AARN is a kind of cousin of DNA,
09:00which makes up our genome.
09:02Researchers think it could have been the first molecule capable of reproducing itself,
09:06a fundamental mechanism for the emergence of life.
09:10The idea is that, in the early days of the Earth,
09:13various chemical compounds were suspended.
09:16At some point, these elements would have come together to form molecules of AARN.
09:21Thanks to its ability to self-replicate,
09:24AARN would then gradually give birth to more complex forms of life.
09:29Although this hypothesis has not yet been proven,
09:32it remains a seductive explanation.
09:34And who knows,
09:35maybe one day we will discover that it is the origin of our existence.
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