Simulating possible chemical processes in the atmosphere of Titan, Saturn's largest moon, an international team including University of Arizona graduate student Sarah Horst and Professor Roger Yelle demonstrated the synthesis of complex organic compounds, such as amino acids and nucleotide bases, which are the basic building blocks of life on Earth.

The molecules discovered include the five nucleotide bases used by life on Earth (cytosine, adenine, thymine, guanine and uracil) and the two smallest amino acids, glycine and alanine.

The intense radiation that hits the top of Titan's thick atmosphere is capable of breaking apart even very stable molecules. The international team wanted to understand what happens as these molecules are broken apart in the atmosphere.

Using radio-frequency radiation as an energy source, Horst's collaborators created cold plasma consisting of nitrogen, methane and carbon monoxide in a reaction chamber. The experiment was the first to produce amino acids and nucleotide bases in an atmosphere simulation experiment without the use of liquid water.

"We can do this entirely in an atmosphere," Horst said. "We don't need liquid water, we don't need a surface. We show that it is possible to make very complex molecules in the outer parts of an atmosphere."

The results not only suggest that Titan's ionosphere could be a reservoir of prebiotic molecules that could serve as the springboard to life, but may offer a new perspective on the emergence of life on Earth as well: Instead of a primordial soup, the first ingredients of life on our planet may have formed from a primordial haze high in Earth's atmosphere.

Moreover, the results show that it may be possible to study these processes in a planetary environment, particularly in the atmosphere of Saturn's moon Titan to gain a deeper understanding of this chemistry.