Complex organic compounds, including many vital to life on Earth, may have been readily produced under conditions that likely prevailed in the primordial solar system, according to a new study.
Scientists at the University of Chicago and NASA Ames Research Center came to this conclusion after linking computer simulations to laboratory experiments.
Fred Ciesla, assistant professor in geophysical sciences at UChicago, simulated the dynamics of the solar nebula, the cloud of gas and dust from which the sun and the planets formed.
Although every dust particle within the nebula behaved differently, they all experienced the conditions needed for organics to form over a simulated million-year period.
“Whenever you make a new planetary system, these kinds of things should go on,” said Scott Sandford, a space science researcher at NASA Ames.
“This potential to make organics and then dump them on the surfaces of any planet you make is probably a universal process.”
Although organic compounds are commonly found in meteorites and cometary samples, their origins presented a mystery.
Sandford has devoted many years of laboratory research to the chemical processes that occur when high-energy ultraviolet radiation bombards simple ices like those seen in space.
“We’ve found that a surprisingly rich mixture of organics is made,” Sandford said.
These include molecules of biological interest, such as amino acids, nucleobases and amphiphiles, which make up the building blocks of proteins, RNA and DNA, and cellular membranes, respectively.
Irradiated ices should have produced these same sorts of molecules during the formation of the solar system, he said.
Ciesla’s computer simulations reproduced the turbulent environment expected in the protoplanetary disk.
This washing machine action mixed the particles throughout the nebula, and sometimes lofted them to high altitudes within the cloud, where they could become irradiated.
“Taking what we think we know about the dynamics of the outer solar nebula, it’s really hard for these ice particles not to spend at least part of their time where they’re going to be exposed to UV radiation,” Ciesla said.
The grains also moved in and out of warmer regions in the nebula. This completes the recipe for making organic compounds: ice, irradiation and warming.
“It was surprising how all these things just naturally fell out of the model,” Ciesla said.
“It really did seem like this was a natural consequence of particle dynamics in the initial stage of planet formation,” Ciesla added.
The study has been published in Science Express.
