Biologists don’t quite agree on exactly where life first arose on Earth. It could have evolved at the bottom of the ocean, in shallow rock pools, or from building blocks delivered by asteroid impacts — or maybe all of them. We’ve known that for life Earth needs water to survive, so life probably evolved there first. But water alone is not enough to fuel life; it also needs energy.
Today most living things get their energy from metabolize Sugars, but these molecules didn’t exist 3.7 billion years ago when life first evolved.
So what sources of energy were available to help Earth’s first inhabitants appear?
Related: What makes the earth so perfect for life?
During the Hadean Age (roughly 4.6 to 4 billion years ago), Earth was mostly an oceanic world, with occasional volcanic islands sticking out of the water. One theory about the origin of life assumes ultraviolet (UV) radiation The sun helped create complex molecules in shallow rock pools on volcanic islands, he said Eloi Camprubi Casas (opens in new tab)a biologist studying the origin of life at the University of Texas Rio Grande Valley.
“UV (radiation) is great because it’s so energetic that it creates ionized molecules, making them more reactive” and more likely to combine into larger, more complex molecules needed to create the building blocks for life, Camprubi-Casas told Live Science. “The problem with UV rays, however, is that it degrades basically everything you have,” Camprubi-Casas said. Even if complex molecules were formed, they would also have broken down due to exposure to the sun.
That’s why Camprubi-Casas and his colleagues hypothesize that life’s origins occurred somewhere far from these warm pools — on the ocean floor, where hot, alkaline water mixed with cool, acidic water, creating a soup of chemical energy that could have sparked a spark for the evolution of life can give.
Deep below the ocean surface, areas of geothermal activity form at plate boundaries as magma rises from the Earth’s mantle. Cold seawater seeps into cracks in these hot areas, loosening minerals from the rock. As the hot water rises from the cracks and flows into the cold ocean, the minerals precipitate, forming “chimneys” of organic material, Camprubi-Casas explained. This liquid is highly alkaline and contains much hydrogen gas, and during the Hadean the Earth’s atmosphere was fuller carbon Carbon dioxide, much of which dissolved in the ocean, making the ocean slightly acidic.
When water from the hydrothermal vents was combined with carbon dioxide dissolved in water, the resulting molecules “became a lot more chemically active, and you can start adding nitrogen to make amino acids, or add nitrogen and oxygen to make the building blocks of DNSsaid Camprubi Casas.
Delivering the building blocks of life from space
One theory about the origin of life on Earth holds that the building blocks of life were supplied by asteroid Effects that were more common in the Hadean than today. On an asteroid, a sheet of ice would have protected simple sugars and small amino acids — the raw materials needed for prebiotic chemistry — from much of the sun’s harsh radiation, he said Partha Bera (opens in new tab)a research scientist at NASA’s Bay Area Environmental Research Institute.
“These bodies are exposed to sunlight for millions of years and produce radicals — drugs — that can react with each other even at low temperatures,” Bera told Live Science. are radicals atomsMolecules or ions with an extra electron, making them ready to react with anything.
After this origin of life hypothesisWhen these asteroids hit Earth, the highly reactive molecules would have mixed with other simple molecules in the ocean to create the complex chemistry needed to start life. In that case, the energy source would also have been geothermal, Bera said.
Because very few (and small) rock samples exist from this period in Earth’s history, it’s impossible to know exactly which energy source — the sun, geothermal chemistry, or geothermal heat — fueled life evolution. But research in labs and much lively debate will help us clarify our possible origins.