Image: Accretion disk around the nascent star HL Tauri located 450 light years away in the constellation Taurus.
This real image of a proto-stellar and therefore protoplanetary nebula reveals the possible locations of planets in formation (dark areas of the nascent system). All forming objects absorb surrounding matter and undergo cataclysmic bombardment.
Credit: ALMA (ESO/NAOJ/NRAO), NSF.
The main hypotheses about the origin of life on Earth are classified into two categories:
- Early Earth hypotheses suggest that the first life forms appeared on Earth in the environment that existed early in the planet's history, 4.54 billion years ago.
- Panspermia hypotheses suggest that life exists in the universe and was brought to Earth from space by meteorites, comets or interstellar dust.
The origin of life on Earth is a complex question that does not yet have a definitive answer. The most accepted theory is the abiogenesis hypothesis, which proposes that life arose spontaneously on Earth from inorganic matter. This theory is based on the idea that conditions on Earth were favorable for the appearance of life around 4.5 billion years ago.
But there is an alternative to abiogenesis: the panspermia hypothesis.
Panspermia is a theory that suggests that life on Earth, or at least some of its basic elements, may have extraterrestrial origins. This theory is based on the idea that life is widespread in the universe and can move from planet to planet via celestial bodies.
In this scenario, organic molecules essential to life (amino acids) or even microorganisms (bacterial spores), would travel through space aboard celestial objects. Then, during the formation of the star system and the planets, the collisions would release these elements which, later, in a favorable environment would evolve towards a more organized life.
The panspermia hypothesis is not yet proven, but it is supported by several arguments and observations that make it plausible.
- Organic molecules have been discovered in numerous meteorites: Orgueil in France (1864), Murchison in Australia (1969), Allende in Mexico (1969), Tagish Lake in Canada (2000).
Each of these meteorites contained a wide variety of organic molecules, including amino acids, nucleic bases and complex carbon compounds. Additionally, each of these meteorites had its own unique chemical composition, which provides interesting insights into the diversity of organic compounds in the universe.
- Comets are also rich in organic molecules. Analyzes of comets Churyumov-Gerasimenko, Hale-Bopp, Wild 2 and Tempel 1 revealed the presence of organic materials, including amino acids.
Comets are considered 5 billion year old objects of the early solar system. Which means that they could contain vestiges of materials from this distant era, that of the formation of the solar system.
In summary, all of these discoveries reinforce the idea that the organic molecules necessary for life can exist and spread throughout the universe. This potential mechanism for the dispersion of life in the universe would mean that life is not a phenomenon unique to Earth, but is very widespread in the universe.
NB: Certain bacteria have the ability to form optional organelles called bacterial spores. Bacterial spores are life forms that are resistant to environmental conditions when they become very hostile. This allows them to survive for millions of years in the space environment.
The Next Step for Intelligent Machines 
The First Step Towards the Emergence of Life 
Phylogenetic Tree of Life 
Formal neuron 
The
shadow biosphere 
Decline of Anthropocentrism 
Artificial intelligence: the explosion of gigantism 
When AI models train on their own data, they go mad! 
Emergence of artificial intelligence: Illusion of intelligence or intelligence? 
The
horseshoe crab, a living fossil! 
Biosignatures or presence of life in the Universe 
Challenge and threat of Artificial Intelligence 
How do machines understand, interpret and generate language in a similar way to humans? 
How does an artificial neural network work? 
Origin of life on Earth: White smoker theory 
Why 37 degrees Celsius? 
Thermodynamics of the sandpile 
Are we alone in the universe? 
Trace of frozen life in Siberia 
Ice cores tell us about our past 
Life evolves in the shelter of glaciations 
Organ regeneration, the salamander 
Cosmic rays and the mutation of species 
Mephisto, the little worm of the depths 
Discovery of solid buckyballs in space 
Bipedalism in
hominids 
Kamchatka
giant crab 
The passage between the inert and the living 
From particles to biochemical life 
Egocentric vision, the man at the center 
Megapod
uses volcanic heat 
Ardi is 4.4 million years old 
Natural selection, the birch moth 
The explosion of life in the Ordovician 
Liquid water, an accelerator of chemical reactions 
Neandertal 
Asimo the
future humanoid 
Conditions for the appearance of life 
Fermi's paradox or Plato's cave 
The Tardigrade, the immortal animal 
Toumaï,
7 million years old 
Border between inanimate and living 
The incredible life of the abyss 
Cyanobacteria create toxic gas 
The short history of the evolution of life 
The smallest frog in the world 
The explanation of the Little Ice Age 
Ashen light, the proofs of life 
Bioluminescence
of living organisms 
Beyond our senses, the great scientific revolutions 
The primitive
soup