The scientists discovered that when an ice sample containing pyrimidine, a ring-shaped molecule of carbon and nitrogen, was exposed to ultraviolet radiation under space-like conditions, uracil, cytosine and thymine, three essential ingredients of life are created. Pyrimidine is commonly found in asteroids, and scientists still have no clue as to its origins.
Uracil, cytosine and thymine are an important part of our genetic code in ribonucleic acid (RNA) and deoxyribonucleic acid (DNA). “We have demonstrated for the first time that we can make uracil, cytosine and thymine non-biologically in a laboratory under conditions found in space,” said Michel Nuevo, research scientist at NASA’s Ames Research Centre, Moffett Field, California, who was part of the team that made the discovery, along with Christopher Materese and Scott Sandford. “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,” he continued.
The team recreated the inhospitable conditions of space by putting the ice block in a machine that creates a vacuum with temperatures around -430°F (-257°C.) To top it off, the chunk of ice was exposed to harsh radiation created by high-energy ultraviolet (UV) photons from a hydrogen lamp.
The radiation resulted in the production of uracil, cytosine and thymine. “We are trying to address the mechanisms in space that are forming these molecules,” Christopher Materese said. “Considering what we produced in the laboratory, the chemistry of ice exposed to ultraviolet radiation may be an important linking step between what goes on in space and what fell to Earth early in its development.”
Exactly how life got its start on Earth is poorly understood. “Our experiments suggest that once the Earth formed, many of the building blocks of life were likely present from the beginning,” said Scott Sandford. “Since we are simulating universal astrophysical conditions, the same is likely wherever planets are formed,” he added.
“Molecules like pyrimidine have nitrogen atoms in their ring structures, which makes them somewhat wimpy. As a less stable molecule, it is more susceptible to destruction by radiation, compared to its counterparts that don’t have nitrogen,” he noted. However, scientists believed that pyrimidine could make it into interstellar dust clouds, they would survive the radiation. The team saw that if pyrimidine is exposed to radiation when frozen in a block of ice that also contains ammonia, methanol or methane, it can survive radiation better as compared to open space conditions.
