This is how scientists explain that life emerged from an inert rock in the middle of space

Explaining the origin of life on our planet (or outside it) is one of the big questions that science has been trying to answer for centuries. We are still far from answering it, but little by little we are taking steps that bring us closer.

Unraveling the origin of life on our planet raises questions that go far beyond the reconstruction of a singular event. For example, we can question whether the “ingredients” from which life was formed arose on our planet or if they arrived on some asteroid.

It is also a question closely linked to another of the great scientific questions, that of whether life has originated in other places in our universe.

Answering all of these questions is still far from our reach and it is we may never find irrefutable evidence about how life emerged on our planet. After all, just as we have fossils that show us its evolution, its origin is too far back in time. Not to mention that we are talking about changes that occurred on a microscopic scale.

Yet the fossil record gives us a very important clue: Life already existed about 3.7 billion years ago. Taking into account that our planet is about 4.3 billion years old, this information greatly limits the period in which life appeared on our Earth.

There are various theories (scientists) about how life emerged on Earth. Some focus on the elements and compounds that could have led to its appearance, others on circumstances or places that could have led to its development.

One of these hypotheses starts from electricity. Lightning is an everyday phenomenon but billions of years ago it could have been the “spark” that detonated the appearance of life. These electrical discharges are capable of transforming simple organic and inorganic compounds, such as water, methane or hydrogen, into complex compounds such as amino acids and sugars, compounds considered the “bricks” of life.

Another hypothesis focuses on clays. The clay materials would have accumulated compounds allowing them to interact with each other while protecting and preserving them.

Another favorable place for the appearance of life are hydrothermal vents. These environments have many ingredients for life. These sources expel water from deeper layers of the Earth's crust, water that has not only heated up along its path, but has also been collecting minerals along the cavities through which it circulated.

At the opposite extreme, life could also have emerged in a frigid environment: ice. This would have fulfilled a function similar to that of clays, concentrating and protecting simple compounds and thus allowing them to interact with each other.

There are those who consider that life did not arise here, but somewhere else, and that it would have been brought to Earth on an asteroid. Let's imagine, for example, that life had emerged on Mars. After its initial evolution, an impact would have caused a piece of Martian rock to be ejected carrying, as if it were a spacecraft, microorganisms that would have ended up crashing on Earth. From then on, life would have prospered on our planet and disappeared from its neighbor.

Providing evidence

Before we explained that the fossil record only allowed us to limit the period in which life would have emerged on our planet. How do scientists searching for this origin work then? They don't lack tools.

Perhaps the most significant experiment in the history of this search is the Miller and Urey experiment. This experiment was carried out in the early 1950s and demonstrated the possibility of an electrical discharge triggering chemical reactions. It was this experiment that validated the first of the hypotheses, demonstrating that a “spark” could convert simple compounds and gases into compound molecules essential for life such as amino acids.

In a recent interview In the diary The countrygeologist Juan Manuel García Ruiz explained that there was still a compound in this experiment that had been overlooked: silica. When his team tried to replicate the experiment in a Teflon container instead of a glass one, the experiment was not successful. The key, explains García Ruiz, was in the glass in which the original experiment was carried out.

The idea that the complex can arise from the simple may generally seem counterintuitive. But it is part of García Ruiz's job. It was precisely through silica that the geologist was able to demonstrate that this type of minerals could create self-organized structures, structures that he called biomorphs because of their appearance. A rounded appearance more similar to that presented by microscopic living beings than to what we can find in minerals.

Astrobiology is another tool that scientists have at their disposal. Studying planets, satellites and asteroids can help us see in them the reflection of our planet billions of years ago.

The existence of hydrothermal activity on some of the moons of our solar system has unleashed the curiosity of astrobiologists. Many are probably rubbing their hands at the possibility of studying on site some places that might not be far from one of the possible scenarios for the appearance of life on our own planet.

To look for evidence in favor of the hypothesis that life did not arise on our planet but arrived on board an asteroid, we must also look beyond the border of our planet. Even a more moderate version of this, which proposes that, if it was not life, perhaps some of its “bricks” could have come from beyond the atmosphere, could have its best evidence in these analyses.

We may never know in detail how life appeared on our planet, but little by little we are answering some of the questions that arise when addressing this topic. However, the mere fact of being able to find these small answers is already something exciting for many.

In Xataka | These Spaniards have just realized that almost everything we know about the origin of life is due to an enormous coincidence

Image | Tim Bertelink, CC BY-SA 4.0 DEED