Here's a recipe: Take a sample of a chemical that would have existed on the early Earth, then zap it with a high-powered laser. The result? Well, it might just be the building blocks that make up DNA, the blueprint of all life on our planet.
That's what researchers in the Czech Republic did in an effort to recreate the conditions on the early Earth at a time when it was being bombarded by large meteorites in a period called the Late Heavy Bombardment around 4 billion years ago.
Some scientists believe the energy of those impacts could have ignited chemical reactions in formamide -- a molecule likely to have existed in early Earth's atmosphere -- to create nucleobases, the genetic components of DNA and RNA.
The impacts on the Earth of meteors, asteroids and even comets may have been the source of energy needed to jumpstart the chemistry of life, researchers at the Academy of Sciences of the Czech Republic say.
Instead of meteors or asteroids, their "impact" was created by shooting high-powered lasers -- at 1,000 joules of power, equivalent to what a nuclear power plant can generate -- into a plasma of ionized formamide gas.
"We want[ed] to simulate the impact of some extraterrestrial body [during] an early stage of the atmosphere of Earth," says study leader Svatopluk Civiš.
Their laser produced temperatures of more than 7,600 degrees Fahrenheit, generating a cascade of X-Rays and extreme ultraviolet radiation that caused chemical reactions in the plasma producing adenine, cytosine, guanine, and uracil, the four organic compounds in RNA.
Many scientists believe RNA would have been the first molecule capable of encoding genetic information.
The fact that the Czech experiment was capable of creating all four of the RNA components is significant evidence for the impact hypothesis and its possible contribution to the emergence of life on Earth, say experts.
"This is, I believe, the first time that all four nucleobases have been made in one set of reaction conditions," says Steven Benner, an astrobiologist at the Foundation for Applied Molecular Evolution in Gainesville, Florida.
Formamide has been the focus of recent research into the conditions and chemicals that may have been necessary for life to begin on Earth.
Formed when hydrogen cyanide reacts with water, it would have been abundant on the early Earth and possesses the elements -- hydrogen, carbon, nitrogen and oxygen -- needed to create prebiotic chemicals.
The Czech researchers combined formamide with clay to mimic a chemical-rich pool sitting on the surface of the ancient Earth, then bombarded it with a laser to see what would be produced.
Their findings are one more link in the evidence chain for how life could have originated on Earth, they reported in the journal Proceedings of the National Academy of Sciences.
"[T]he emergence of terrestrial life is not the result of an accident but a direct consequence of the conditions on the primordial Earth and its surroundings," the researchers wrote.
