The “idea” that life may have come to Earth from other bodies in space does not necessarily imply that living organisms themselves were transported to our planet from elsewhere and subsequently evolved. This theory also encompasses the possibility that the compounds necessary for the existence or facilitation of life arrived on Earth (or any other planet) at a later stage.
In fact, this theory addresses the inevitable and provides satisfactory answers to many lingering questions. In short, it is not a baseless theory. Let’s present some fundamental information, avoiding sensationalism and sterile debates:
On an Earth-sized planet, many of the substances essential for life “as we know it today” may not have been present or formed due to the intense heat during its early formation stages. At least, our current theories suggest such a scenario.
Certainly, we cannot be entirely certain about this, but according to our formation theories, some of the complex molecules crucial for life could not have originated here. Therefore, it is plausible that some of the intricate molecules forming the foundation of life may have arrived on Earth in some form later on.
For instance, retaining the quantity of water that exists on Earth today would have been impossible in the extremely hot environment during Earth’s formation. Without an external water supply, life as we know it, heavily reliant on water, would not have been feasible. Research indicates that Earth’s water accumulated through an intense meteorite/comet bombardment that occurred around 3.5 billion years ago.
Likewise, observations have long revealed that the building blocks of certain amino acids necessary for life, as well as various organic molecules, can easily form in space on meteorites and even in gas and dust clouds in interstellar space.
Subsequently, it is not improbable that some of these crucial molecules formed in non-planetary environments could have disseminated to planets within the habitable zone (e.g., Earth in our case) via meteorites, playing a role in the emergence of the first living organisms. Perhaps, with a high probability (if extraterrestrial life exists), this scenario is commonplace.
In summary, according to the panspermia hypothesis, life might have arrived on Earth through primitive single or multicellular organisms carried by meteorites. It is important to emphasize that living organisms do not necessarily have to be the carriers; rather, the delivery of organic molecules to Earth through meteorites could have triggered the emergence of life through a natural evolutionary process.
Note: Panspermia is an “idea” supported by substantial evidence. It offers a robust perspective on how molecules capable of creating life on Earth and initiating evolution may have arrived. By observing this notion today, both on Earth and on other planets, we are evaluating the validity of this idea.