Geochemical processes in ancient hydrothermal systems could have enabled key steps towards the origin of life on our planet, according to new research from Newcastle University. The study provides fresh insights into how the first biological molecules were synthesized on early Earth.
Key Building Blocks of Life Formed in Hot Springs
The new findings, published today in Nature Reviews Earth & Environment, suggest that hot springs on the seafloor could have acted as chemical reactors, bringing together ingredients key to developing the complex organic molecules that make up RNA, proteins and lipids – the building blocks of life.
“The origin of life on Earth is one of the most fascinating and challenging questions in science,” said lead author Dr. Stefano Bonaglia, Leverhulme Early Career Fellow at Newcastle University. “Our results suggest that the geological conditions on early Earth could have facilitated important steps towards the origin of life in hot, geochemically active environments.”
The researchers theorize that rapid heating and cooling cycles in the hydrothermal systems could have driven a non-enzymatic synthesis of RNA. They also describe how minerals and reduced gases in alkaline hydrothermal fluids could have contributed to the synthesis of acetyl-CoA and pyruvate – molecules vital to early metabolism.
“This is an exciting result because it suggests vertical hydrothermal chimneys and hydrothermal fields could have provided the right ingredients in the right conditions for RNA synthesis on early Earth,” Dr. Bonaglia said.
Conditions Just Right for Building Blocks to Form
In chemical reactions modeled by the Newcastle team, they found that wet-dry thermal cycling at temperatures reaching 120°C, such as those that would have occurred as alkaline hydrothermal fluids mixed with primordial ocean water, enabled the formation of the pyrimidine ribonucleotides. These are the building blocks of RNA.
“The remarkable ability of RNA to store information and catalyze chemical reactions suggests that if its nucleotides were able to form on early Earth, then RNA polymers could emerge,” explained Dr Bonaglia. “Our results substantiate Charles Darwin’s speculate about life having originated in a ‘warm little pond’.”
|Sea floor hot springs
|Amino acids, minerals, gases
|Heating and cooling cycles
|Wet-dry cycling, 120°C heat
Table summarizing how different hydrothermal environments could have enabled key steps in the origin of life through production of building blocks essential to early metabolism and information transfer.
The team also found clues as to how acetyl-CoA – a key compound in metabolism – may have emerged through reactions involving minerals and reduced gases dissolved in alkaline hydrothermal fluids. Their model outlines a possible mechanism through which the complexity and diversity found in modern biochemistry could have arisen gradually in hydrothermal systems.
Next Steps: Testing Theory in Lab Experiments
“Unraveling the origins of life question is fundamental to understanding our place in the universe,” said Dr. Bonaglia. “Our results highlight how geological, chemical and physical processes on early Earth could have created the building blocks that kick-started life.”
The researchers said the next step is to reproduce some of the chemical reactions described in their study in the lab to see if the mechanisms stand up to experimental testing. They also plan to further probe the properties of hydrothermal chimneys and mineral cells as chemical reactors that concentrate, isolate and compartmentalize key ingredients for life.
“We’re excited to test these hypotheses experimentally and hope our next round of results will better clarify the processes that gave rise to RNA, acetyl-CoA and other prebiotic molecules,” Dr. Bonaglia concluded.
The breakthrough study was conducted in partnership with the Earth Sciences department at Durham University, and received funding from Newcastle University, the Leverhulme Trust, and the Engineering and Physical Sciences Research Council.
Implications: Are Hot Springs the Cradles of Life?
The new insights bolster the theory that life on Earth originated in hydrothermal environments, which remain promising locations to investigate the origins of life – both here and potentially elsewhere in the Solar System.
“Research by NASA and others has shown that Mars and some icy moons around the gas giants like Enceladus may have similar hot spring environments to those that were present on the early Earth,” Dr. Bonaglia said. “It’s possible that in those locations too, key ingredients came together to spark life.”
Icy moons with subsurface oceans such as Enceladus and Europa are priorities for astrobiological studies due to their potentially habitable environments hidden below an icy crust. The insights from Dr. Bonaglia’s team provide clues as to what chemical signatures could indicate prebiotic chemistry at work.
“As we continue investigating places in our Solar System that may host habitable environments, understanding the signatures of biological molecules coming together could help identify the cradle of life on another world,” Dr. Bonaglia said.
Through studying deposits around terrestrial hot springs millions and billions of years old, scientists may also find chemical traces providing evidence to support or refute their models.
“Much research is still needed to elucidate all the steps in the transition from prebiotic chemistry to fully-fledged biochemistry, but we think we are on the right track having established a mechanistic framework for key stages in that process here on Earth,” concluded Dr. Bonaglia. “Perhaps most excitingly, those first steps towards life may not have been confined solely to our planet.”
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