NASA scientists studying the origin of life have reproduced three key components of our hereditary material in the lab.
Researchers discovered that an ice sample containing pyrimidine exposed to ultraviolet radiation under space-like conditions produces these essential ingredients of life.
Pyrimidine is a ring-shaped molecule made up of carbon and nitrogen and is the central structure for uracil, cytosine, and thymine, which are all three part of a genetic code found in ribonucleic (RNA) and deoxyribonucleic acids (DNA).
RNA and DNA are central to protein synthesis, but also have many other roles.
"We have demonstrated for the first time that we can make uracil, cytosine, and thymine, all three components of RNA and DNA, non-biologically in a laboratory under conditions found in space," said Michel Nuevo, research scientist at NASA's Ames Research Center, Moffett Field, California.
"We are showing that these laboratory processes, which simulate conditions in outer space, can make several fundamental building blocks used by living organisms on Earth," said Nuevo.
An ice sample is deposited on a cold substrate in a chamber, where it is irradiated with high-energy ultraviolet (UV) photons from a hydrogen lamp.
The bombarding photons break chemical bonds in the ices and break down the ice's molecules into fragments that then recombine to form new compounds, such as uracil, cytosine, and thymine.
During their experiment, researchers exposed the ice sample containing pyrimidine to ultraviolet radiation under space-like conditions, including a very high vacuum, extremely low temperatures, and harsh radiation.
They found that when pyrimidine is frozen in ice mostly consisting of water, but also ammonia, methanol, or methane, it is much less vulnerable to destruction by radiation than it would be if it were in the gas phase in open space.
Instead of being destroyed, many of the molecules took on new forms, such as the RNA/DNA components uracil, cytosine, and thymine, which are found in the genetic make-up of all living organisms on Earth.
"Nobody really understands how life got started on Earth. Our experiments suggest that once the Earth formed, many of the building blocks of life were likely present from the beginning," said Christopher Materese, another researcher at NASA Ames who has been working on these experiments.
