Scientists think that water and organic molecules come together in the coldest places in space to begin the chemical reactions necessary for organics to evolve into prebiotic molecules – molecules that are precursors of life. Ice and organics could have hitched a ride to Earth on comets and asteroids, where they could have formed the building blocks of life as we know it.
Researchers at NASA’s Jet Propulsion Laboratory in Pasadena, California, are trying to better understand that process, and how life may have formed on Earth, by firing lasers at icy carbon-laden molecules in a lab.
Principal scientist Murthy Gudipati explained to CNN by e-mail: "In the cycle of formation, evolution, and death of stars, two key components of life (as we know of it): water and organic matter, evolve intimately with the third component energy (radiation) at every stage of this cycle – even at the coldest regions of the universe."
Gudipati and his team are studying polycyclic aromatic hydrocarbons, known as PAHs. On Earth, you might find these as air pollutants from engine exhaust, or in barbecue pits or other places where combustion occurs; in space, they're found in comets and asteroids, and swirling around stars.
"We were surprised to see organic chemistry brewing up on ice, at these very cold temperatures in our lab, " Gudipati stated in a release from JPL.
Those very cold temperatures? About 450 degrees below zero Fahrenheit, cold enough to mimic the cold of space. Then the researchers hit the PAHs – the organic particles – with a laser, in order to see the results of the chemical reaction in that environment.
The study revealed that it's possible for organic materials to start the reactions they must go through to become prebiotic, while still frozen. The PAHs incorporated hydrogen atoms into their molecular structures and lost their circular bonds – in short, they became more complex organic molecules.
So what's special about that? These are the types of reactions and changes required for simple organic molecules to form amino acids, the building blocks of proteins, and nucleotides, required to form DNA. But there are some missing steps still to be discovered to explain how these particles could go from being ice and organic molecules to life.
The results of the study, conducted by Gudipati and his colleague Rui Yang at JPL, were published recently in The Astrophysical Journal Letters.
Gudipati told CNN, "The next step is to understand how, from simple organics, the complex prebiotic molecules evolve in these ices as the ice particles make their journey from the interstellar medium to form new stars, solar systems, comets, asteroids, and eventually Earth-like bodies."
He concluded, "This is one way looking into our past – how life evolved on Earth, or looking into the future – how life could evolve on other solar systems."