A Miller–Urey broth mirrors the mass density distribution of all Beilstein indexed organic molecules

Abstract

The Miller–Urey experiment became a paradigm for spontaneous generation of biomolecules on the prebiotic Earth. In the experiment water, methane, ammonia and hydrogen gases are submitted to electric discharges. New molecules emerge and accumulate in liquid water to form a rich organic solution. Although many important biomolecules such as amino-acids have been isolated from a Miller–Urey broth, it is unclear how many different molecules the experiment is able to produce. Here we analyze the prebiotic broth by liquid chromatography and high-resolution mass spectroscopy. We find that the experimentally determined molecular mass density distribution from the Miller–Urey experiment reproduces the distribution of all organic molecules (regardless of their elemental composition) indexed in the Beilstein database. The observed mass density distribution exhibits paretian behavior: it closely follows a log-normal distribution except for its tails where it approaches a power-law. Simple growth models reproduce the experimentally observed mass distribution to a lesser extent than the Beilstein data. We conclude that molecular growth processes are unlikely to limit the experimental outcome, rather the Miller–Urey experiment seems to explore the entire range of prominent, stable masses of molecules that are part of the Beilstein/Reaxys database and made from the same atomic elements. We suspect that in principle the experiment can, at least statistically, produce any small organic molecule that exhibits sufficient stability as part of the broth.

Keywords

• Miller–Urey
• prebiotic broth
• Beilstein
• mass density distribution
• spontaneous molecule formation
• aggregation