Self and the Beginning of Life 37“9x6” b2726 Self and the Phenomenon of Life: A Biologist Examines Life from Molecules to Humanityappearing like smoke or nebulous clouds (Fig. 3.10). Cosmic dust and
clouds are the intermediates in the endless life-death cycles of the stellar
world. Spectroscopic analysis of cosmic dust revealed the presence of many
simple organic compounds containing carbon, oxygen, and nitrogen, in
addition to hydrogen. Heavy elements are also present. Many of these are
potential starting materials for the complex molecules of life (Table 3.7).
Next, can we simulate in the laboratory what went on in nature,
starting from the molecules found in outer space or the early Earth? In
1953, Stanley Miller and Harold Urey produced a trace of amino acids
upon concocting for two weeks a mixture of water, hydrogen, ammonia
and methane, under constant electric spark discharge. At least 13 amino
acids (mainly glycine and alanine) that can support life were identified
in the mixture, amidst a host of unknown materials.^18 No nucleobases
were found. Although the yield of the amino acids was minuscule, and
the experimental conditions were subsequently considered not in con-
formity with those of early Earth (too much hydrogen), the experiment
opened the door to the possibility of abiogenesis of life.
In 1961, Joan Oró synthesized adenine (a purine nucleobase) out
of hydrogen cyanide (HCN), ammonia and water.^19 In a summary article
Fig. 3.10. Infrared image of Trifid Nebula in the constellation Sagittarius. Nebular
clouds like this are made of tiny interstellar particles called cosmic dust, and are believed
to be nurseries for new stars. Cosmic dust contains simple organic molecules necessary
for life. [US Natl. Aero. Space Ad.]