Imagine Earth 4 billion years ago. The world was covered in an acidic ocean, its bottom studded with mineral chimneys or hydrothermal vents. These were not ordinary chimneys. They had pores that allowed selective molecules to pass through, setting up a chemical gradient.
The vents were the origins of all life on earth, according to a 25-year-old theory proposed by Mike Russell, a research scientist at NASA’s Jet Propulsion Laboratory, that is gaining traction in the astrobiology community. NASA’s Astrobiology Institute has invested $8 billion in proving the theory.
The water inside the vent was hot, and it slowly reacted with iron and other minerals to produce a basic environment – like baking soda in water. The ocean outside the vent was acidic and cool. Perfect conditions for a pre-historic membrane gradient.
That may sound familiar from 9th grade Biology. Our bodies too also have vital membrane gradients that allow us to generate and use up energy in the form of ATP (adenosine triphosphate). ATP moves along a membrane inside the cell, becoming energized, and then is moved across another membrane into a chamber where the energy is used up by our body. Simply put, we wouldn’t exist without membranes.
The hydrothermal vents were the gradients of early life, according to the theory called “metabolism first” proposed by Russell. Life forms figured out how to tap energy from these vents, and all other processes, such as the replication of DNA, came after.
That’s a tough theory for scientists to prove. Our modern oceans are no mimics of the hostile conditions of early Earth. The only way to go about this would be to reconstruct one of these ancient vents in the lab.
So, Russell and his colleagues have built a system resembling a “pillared Emerald City in the Wizard of Oz,” NASA wrote in a release.
They have manufactured a gel that resembles the porus vents of yore, as Nature reported in 2009. A series of glass tubes, thin barrels and valves recreate as-best-as-possible the early conditions. The goal is to see if the system spontaneously generates organic molecules such as ethane, methane and even simple amino acids which are the building blocks of proteins that form the basis of life.
So far, the scientists have been able to produce acetate, a compound generated by a pathway present in many bacteria, according to a recent study. Acetate can be a base for many key biological molecules.
In fact, compare some of the most ancient enzymes in life forms — acetyl coenzyme A synthase, for instance, which helps us generate energy — to minerals at these vents, and you’d see striking structural similarities, according to a recent study in Biochimica et Biophysica Acta.
All this is evidence in favor of Russell’s theory.
“What we’re trying to do is to climb down and create the conditions for the very first steps to the beginning of life as we know it,” said Russell in a statement. “That’s the hard part.”
Image: Hydrothermal vents. Credit: NOAA
Image: Lauren White, a member of the Russell’s team, is turning on a valve. This will send ocean water through a membrane that mimics early vents to see the process generates organic molecules that could be the basis of life. She will alternate the ocean water with alkaline liquid that mimics conditions inside the early hydrothermal vents. Credit: NASA/JPL-Caltech.