Life on Earth first formed near deep-sea vents, not shallow pools, new research reveals. The basic idea is not new, but the origin of life is one step closer to being understood, a new investigation from University College London reveals.
A new study from the University College London (UCL) suggests that life on Earth may have developed from the odd chemistry surrounding deep sea vents. This finding could also offer a new look at how life might develop on other worlds.
Life first developed on Earth not long after our world solidified and the first ocean(s) formed. Estimates for the first appearance of life on Earth range from roughly 3.8 billion to more than 4.3 billion years before our time. By comparison, our home world is thought to be be just 4.54 billion years old, and the oceans formed 4.4 billion years ago.
Scientific ideas about the development of life on Earth traditionally postulated that the first stirrings of life began in shallow pools on the land, where the Sun could provide energy needed to drive chemical reactions. In recent years, many researchers have developed the theory that heat and chemicals delivered by deep sea vents on ocean floors may have provided the conditions needed to spark life on Earth. However, many experiments have come up short of proving the idea.
“There are multiple competing theories as to where and how life started. Underwater hydrothermal vents are among most promising locations for life’s beginnings — our findings now add weight to that theory with solid experimental evidence,” Professor Nick Lane of the University College London (UCL) stated.
You’re in Hot Water Now…
Deep under the Earth’s seas, under these vents, water comes into contact with material lying beneath the seafloor. Heated by magma from under the ocean floor, water heats and rises, carrying minerals from under the surface into the depths of the ocean.
The process creates a warm, highly-alkaline environment, teeming with hydrogen, forming mineral-rich chimneys. This water is so enriched by minerals that it can becomes colored, earning some chimneys the classification of black (or white) smokers.
Black smokers are the hotter of the two types of structures, where temperatures reach 350 C (700 F), hot enough to melt lead. White smokers are far closer to temperate, having peak temperatures between 40–90 C (100 and 200 degrees F). While black smokers emit large proportions of sulfides, white smoker emissions are rich in calcium, magnesium, silicon and barium.
Energy produced by deep sea vents drives reactions between hydrogen and carbon dioxide, potentially forming the precursors to cellular life.
“They may be different but all hydrothermal vents tend to have not just bacteria and other microorganisms, but large, multicellular, complex organisms as well,” said Morgan Cable, a research scientist who studies ocean worlds at NASA’s Jet Propulsion Laboratory.
On Earth, both types of features host rich ecosystems, including octopi, crabs, and tapeworms and tubeworms.
It Takes All Types!
Previous experiments aimed at forming protocells under vent-like conditions failed to produce viable protocells. These formations, composed of a membrane, enclosing an aqueous solution, are generally considered a necessary step during the production of cell-based life.
Protocells formed from naturally-occurring fatty acids under vent-like conditions have quickly fallen apart. But, these earlier experiments greatly limited the sizes, and varieties of, ingredients available for the production of the structures.
“Other experiments had all used a small number of molecule types, mostly with fatty acids of the same size, whereas in natural environments, you would expect to see a wider array of molecules,” explained Dr. Sean Jordan of UCL.
The team provided their experiment with a wide range of fatty acids and fatty alcohols, a better representation of the natural environment.
This new study suggested that, rather than inhibit the formation of life, the highly-alkaline high-temperature environment around deep sea vents may be a critical factor in the formation of primitive life.
Long chains of carbon, essential to life on Earth, require the significant heat provided by the vents, and the alkaline environment helped to stabilize the electric charge of the structures as they formed. Salt water also played a significant role in the formation of protocells, as fat molecules bonded more quickly in a saline environment than in fresh water, the study found. Production of the membranes in the experiment peaked around 70 degrees Celsius (158 Fahrenheit), a temperature which would quickly kill most organisms.
Despite the harsh conditions — or perhaps, because of them — some of the oldest fossils ever found on Earth formed around deep sea vents.
I Hear the Skiing on Europa is Fantastic…
Throughout our solar system, several moons orbiting the outer planets hold onto oceans of water beneath a frozen surface. Deep beneath these alien seas, vents similar to those on Earth might form, although they would need a source of energy to drive them. Many exoplanets orbiting other stars could, theoretically, also have vents much like those on Earth, sparking life on distant worlds.
“Strange, isn’t it, Jean-Luc? Everything you know… your entire civilization… it all begins right here in this little pond of goo. It’s appropriate somehow, isn’t it? Too bad you didn’t bring a microscope — this is quite fascinating. Here they go… the amino acids are moving closer… closer…closer…Ohhhh! Nothing happened! You see what you’ve done?” — Q, Star Trek: The Next Generation
“Space missions have found evidence that icy moons of Jupiter and Saturn might also have similarly alkaline hydrothermal vents in their seas. While we have never seen any evidence of life on those moons, if we want to find life on other planets or moons, studies like ours can help us decide where to look,” Lane described.
One of the most likely places to find deep sea vents on other worlds may be on Enceladus, one of the many moons of Saturn. Just 500 kilometers (300 miles) in diameter, this world is smaller than Pluto’s moon, Charon.
Despite its diminutive size, Enceladus was the first moon of the solar system where jets of water vapor were seen shooting water vapor high above the surface. Due to its small mass, there is little gravity to hold onto the water vapor, and most of it is lost to space.
In 2013, the Hubble Space Telescope (HST) spotted jets of water vapor above the surface of Jupiter’s moon, Europa. That moon is already known to possess vast oceans of liquid water beneath its icy surface. Both Enceladus and Europa are believed, by many researchers, to be one of the most likely places to find life in the Solar System.
The new study on the formation of life around deep sea vents was published in the journal Nature Ecology & Evolution.
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