Life as we know it is mostly composed of elements such as carbon, oxygen, and nitrogen. Although these elements were common in the environment 4 billion years ago, none were present in the form of proteins, DNA, or vitamins, the key building blocks of life. The question scientists ask, then, is how life could have emerged in an environment that contained essential elements such as carbon dioxide and nitrogen gases in forms that were nearly impossible to obtain.
A team of scientists from multiple American universities has joined forces to answer that question. They argued that an external energy source was needed to convert carbon dioxide and nitrogen into more reactive, life-accessible compounds. On early Earth, these energy sources may have included radiation from the sun, deep-sea hydrothermal vents, volcanoes, and even meteorite impacts. Previous researchers have shown that lightning can have some effect. nitrogen and phosphorus Compounds become more available. These scientists therefore proposed that lightning may have provided the energy that made carbon dioxide and nitrogen gases available to early life.
To test their hypothesis, scientists built a system in the lab that mimics early lightning strikes on Earth. They were placed in a 50 milliliter (about 2 ounce) glass flask filled with 10 milliliters (about 0.5 ounces) of liquid water and an atmosphere representative of early Earth, consisting of 80% carbon dioxide and 20% nitrogen. Sparks flew. To recreate a realistic environment, we conducted four experiments with varying salinity concentrations in the water. Two are similar to the ocean, and two are similar to fresh rainwater, which contains very little salt.
For the last variable, minerals commonly found on Earth, such as calcite and magnetite, were introduced into one flask with salt and one without salt. Scientists hypothesized that lightning could cause these minerals to react with carbon dioxide and nitrogen, producing a wider range of molecules than experiments without minerals.
The research team used a variety of analytical techniques to analyze the gas and liquid in the glass flask before and after the lightning discharge. To analyze the gas, they used two techniques that are sensitive to gas molecules. infrared spectroscopy and gas chromatography. This allowed them to detect compounds containing carbon and nitrogen remaining in the atmosphere inside the flask. They measured various properties of carbon- and nitrogen-rich compounds found in the liquid using chemical analyzes such as: ultraviolet absorption spectroscopy, capillary electrophoresis, nuclear magnetic resonance, and Mass spectrometry. These techniques have helped scientists more precisely identify molecules in liquids.
The scientists compared the types and amounts of molecules in each salt and mineral combination before and after release. Overall, they found that bacteria synthesize primarily the same molecules from atmospheric nitrogen. nitrogen oxides, ammoniaand nitrateformed in amounts comparable to concentrations in modern soils. They also acetate and formateThese are both carbon-rich compounds found in all known living organisms in varying concentrations.
They found that in experiments with more salt, the yield of both nitrogen- and carbon-containing molecules was on average three times greater. However, in experiments with minerals, the yield of each molecule was 1.5 times lower, but the variety of chemicals produced was 20% higher. The scientists argued that the minerals caused more molecules to react in the flask, creating a greater variety of chemicals in the water.
The scientists highlighted that their results suggest that lightning may be more effective than other energy sources at producing molecules containing nitrogen and carbon that can be used by life. They also found that lightning striking mineral-laden water that mimics wet ground produced more of the molecules necessary for life than striking pure salt water. They hope that future scientists will conduct further experiments with more types of minerals to explore the full potential of these reactions and whether they could have contributed to the formation of life and its early evolution. He suggested further testing was needed.
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Source: sciworthy.com
