Sulfur may have played a key role in the origin of life on Earth

A recent University of Arizona study investigates the role of sulfur in the origin of life on Earth. Scientists recalled earth’s tumultuous beginnings, with its volcanic landscapes and charged atmosphere, to understand how life could emerge from such a seemingly inhospitable environment.

Sulfur isn’t a glamorous star of the periodic table. But it’s a chemical shapeshifter, taking on various forms. It helps form proteins, vitamins, and even the building blocks that make up our own DNA.

However, for early earth, the question becomes whether the right kind of sulfur was around to kickstart the whole process.

RNA world and sulfite

The basis of the study is a theory called the “RNA world.” You might have heard of DNA, its more famous cousin, but RNA is a versatile multitasker. The big idea is that RNA might have been able to both store genetic information and act as a simple enzyme to start the chemical reactions that ultimately led to life.

However, making RNA without the complex biological machinery of modern cells needs a special type of sulfur called “sulfite.”

“For about 50 years, people have tried to figure out how to make RNA without enzymes, which is how biology does it,” explains Dr. Sukrit Ranjan, a leading researcher investigating this mystery.

Searching for sulfur on early Earth

The team decided to hunt for clues about how much sulfite might have been available on the young earth. The problem is, sulfur loves to react. Especially in today’s world, it’s quickly gobbled up by oxygen.

“Of all the atoms that stock the prebiotic shipyard, including carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur, sulfur is perhaps the thorniest,” notes Sonny Harman, a scientist at NASA.

But billions of years ago, earth’s atmosphere had very little oxygen, meaning sulfite might have stood a better chance. Could there have been enough to create the building blocks of RNA?

“No one has actually looked into this in depth outside of other contexts, mainly wastewater management,” Dr Ranjan pointed out. The scientists recreated early earth-like conditions in the lab to uncover the secrets.

Stability and instances of sulfite

Contrary to assumptions, the study exposed a previously unknown characteristic of sulfite – it undergoes disproportionation. This reaction could significantly impact our understanding of its availability for prebiotic chemistry.

“Once it’s in the water, what happens to it? Does it stick around for a long time, or does it go away quickly?” Dr Ranjan posed a critical question.

Sulfites could remain stable longer in the absence of oxygen, potentially contributing to the formation of life-essential molecules.

Ranjan’s research extends to identifying modern environments that could mirror the conditions of early earth, such as the sulfite-rich pools in Yellowstone National Park.

These sites offer valuable clues about the types of environments that could have supported the accumulation and chemical processing of sulfur compounds.

The implications of this study reach beyond understanding sulfur’s role in early earth chemistry. Researchers express excitement about the potential for future research. It could involve integrating geological evidence and biological experiments to further explore the origins of life.

Significance of sulfur and life on Earth

“If true, this implies that sulfite was present in the natural environment in at least some water bodies, similar to what we argue here,” Dr. Ranjan said.

His work hints that some of earth’s oldest microbes might have evolved precisely in those kinds of environments. And now, even geologists are on the hunt, searching ancient rocks for hidden signs that these life-friendly chemical hotspots existed billions of years ago.

The investigation is far from over, but sulfur, the overlooked element, may have a surprising story of its own to tell.

More about the element sulfur

As discussed above, sulfur, symbolized as S and occupying the 16th position on the periodic table, stands as one of the most abundant elements on Earth.

Primarily found in volcanic emissions and mineral deposits, this nonmetallic element is renowned for its bright yellow crystals and distinctive odor when combusted.

Sulfur plays a crucial role not only in the environment but also in various biological processes, marking its significance across the realms of industry, agriculture, and biochemistry.

Sulfur in nature and its environmental impact

In the natural world, sulfur cycles through the air, water, and soil, participating actively in the Earth’s systems. Volcanic activities release vast quantities of sulfur dioxide (SO2) into the atmosphere, a phenomenon critical for understanding climate dynamics and acid rain formation.

Furthermore, sulfur’s presence in the ocean contributes to the global sulfur cycle, influencing marine ecosystems and the atmospheric concentrations of various sulfur compounds.

Significance of sulfur and life on Earth

Biologically, sulfur is indispensable. It is a vital component of amino acids such as methionine and cysteine, which are essential for protein synthesis in all living organisms. Sulfur’s role extends to the realms of vitamins and coenzymes, where it is involved in numerous metabolic reactions.

This element’s significance is highlighted by its contribution to the structure and function of enzymes and its involvement in the detoxification processes within organisms.

Sulfur in industry: A multifaceted resource

Industrially, sulfur’s applications are diverse and impactful. It is a key ingredient in the production of sulfuric acid, one of the most widely used chemicals in the world, essential for manufacturing fertilizers, batteries, and various other chemicals.

Beyond this, sulfur finds use in the vulcanization of rubber, enhancing its strength and elasticity. The element’s antifungal and antibacterial properties also make it a valuable component in pharmaceuticals, pesticides, and preservatives.

Future of sulfur research and applications

As research into sulfur continues to advance, its potential applications expand. Innovations in sulfur-based battery technologies promise more efficient energy storage solutions, while its role in reducing mercury emissions from industrial processes highlights sulfur’s contribution to environmental protection efforts. The ongoing exploration of sulfur’s biochemical functions may further unravel its mysteries, offering new insights into health and disease prevention.

In summary, sulfur’s journey from the depths of the Earth to its pivotal roles in biological systems and industrial applications underscores its multifaceted importance. As we delve deeper into the understanding of this enigmatic element, its potential to drive scientific and technological advancements continues to grow, marking sulfur as a cornerstone of both natural processes and human innovation.

The full study was published in the journal AGU Advances.

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