Chapter 1: The Enigma of Life’s Emergence

How did life originate on a barren planet? Was it a mere coincidence, or did it develop through a series of stages? Furthermore, could other celestial bodies have fostered life, and if so, which ones? After numerous setbacks, emerging research is beginning to shed light on these fundamental questions.

A recent study published in the journal Astrobiology proposes that life may have formed through a gradual process in and around geothermal springs on a volcanic island approximately four billion years ago. This concept aligns with previous theories suggesting that life began with basic chemical components forming in an atmosphere markedly different from what we experience today.

Central to this process is a wet-dry cycle, where water evaporates and returns, playing a crucial role. The evaporation leads to the aggregation of chemical precursors into cell-like entities encased in lipid membranes, creating a moist environment filled with water and various carbon compounds. Each of these structures acts like a tiny laboratory, conducting its own experiments.

While these primitive structures are far simpler than modern living cells, they undergo a form of natural selection. As water returns, weaker structures are dismantled while more resilient ones endure. During the driest phases, these cell-like forms merge partially, allowing them to share successful experimental outcomes. This marks the rudimentary beginnings of what will eventually evolve into Darwinian evolution.

This research, spearheaded by Bruce Damer, a Canadian-American systems theorist, and David Deamer, an American biologist, builds on the contributions of various researchers. Notably, Australian astrobiologists Tara Djokic and Martin van Kranendonk studied ancient mineral formations, known as stromatolites, in the Pilbara region of Western Australia, which suggest early microbial life associated with geothermal springs. Other contributors include British biophysical chemist Marc Rodriguez-Garcia, who explored how evaporating water can link amino acids into peptide chains, and Israeli geneticist Doron Lancet, who proposed a concept of autocatalytic evolution independent of genetic coding.

Damer and Deamer argue that among the various early Earth environments—such as ocean vents and tidal pools—land-based hot springs would have been optimal for "Goldilocks chemistry," which facilitates the formation of life's building blocks. This environment would have had lower mineral salt concentrations and higher carbon compound levels, resulting from rainwater that seeps into the ground, heats up, and eventually emerges as geysers.

The authors do not claim that life on Earth must have originated exactly as they describe; rather, they suggest that this pathway is a plausible scenario for life's emergence, which could also occur on other planets given similar conditions.

This new perspective challenges two long-held beliefs: that life began in the ocean and that self-replicating molecules predated cellular structures. While these ideas have not been definitively proven, they have been widely accepted in scientific discourse. Such assumptions have often overshadowed other potential explanations.

In contrast, the authors' findings resonate with earlier notions that the evaporation stage of the wet-dry cycle resembles salt crystallization, echoing a theory proposed over 90 years ago: that the growth of living matter parallels the growth of crystals. This concept was notably advanced by physicist Erwin Schrödinger in his 1944 work, What is Life, and earlier by biochemist Alexander Oparin in his 1924 book, Origin of Life.

To gauge the potential for life in the universe, we need to answer two critical questions: how many planets can support life, and among those, how many actually do? Some theories posit that the emergence of life is a highly improbable event. French biochemist Jacques Monod famously remarked that life is a rare occurrence in the universe, suggesting that our existence may be a product of chance.

Japanese astronomer Tomonori Totani recently proposed that the probability of life emerging might be so low that it is unlikely to have happened elsewhere in the observable universe. He theorizes that if our universe is just a small section of an even larger cosmos, the chances of life emerging could be more feasible.

However, emerging evidence suggests that the assumptions underpinning these theories might be flawed. The idea that life’s intricate genetic structures are prerequisites for evolution may not hold true, as low-probability events may not be the best explanation for Earth's life.

Any planet with conditions similar to early Earth—comparable chemistry, volcanic islands, and hot springs—could potentially yield similar life forms. While some of these may evolve into larger organisms, the likelihood of this happening remains uncertain.

Nevertheless, the proposed model does not imply that life will thrive wherever there is liquid water. For instance, as Damer and Deamer highlight, a wet-dry cycle conducive to cell formation would not occur on moons like Europa due to its thin atmosphere preventing liquid water on the surface.

Conversely, Mars may have been capable of supporting life through similar evaporation cycles four billion years ago when it possessed a thicker atmosphere and surface water. While the authors do not address Saturn's moon Titan in their paper, previous studies have shown that Titan's thick atmosphere, rich in carbon compounds, along with its liquid methane and ethane bodies undergoing cycles of evaporation, could provide a fascinating area for future research.

Looking beyond our solar system, the revelations from this model suggest that the number of living organisms in the galaxy could be astronomical, given what we now know about the prevalence of planets orbiting stars.

In essence, it appears that the universe may be teeming with the potential for life.

The first video titled "How did life on Earth begin? | Science Nation" delves into the scientific investigations surrounding the emergence of life on our planet, offering insight into the processes that may have led to its formation.

The second video "Where is the Origin of Life on Earth?" explores various hypotheses regarding the locations and conditions that may have enabled life to arise on Earth.