Toward RNA Life on Early Earth: From Atmospheric HCN to Biomolecule Production in Warm Little Ponds

Abstract

The origin of life on Earth involves the early appearance of an information-containing molecule such as RNA. The basic building blocks of RNA could have been delivered by carbon-rich meteorites or produced in situ by processes beginning with the synthesis of hydrogen cyanide (HCN) in the early Earth’s atmosphere. Here, we construct a robust physical and nonequilibrium chemical model of the early Earth’s atmosphere. The atmosphere is supplied with hydrogen from impact degassing of meteorites, water evaporated from the oceans, carbon dioxide from volcanoes, and methane from undersea hydrothermal vents, and in it lightning and external UV-driven chemistry produce HCN. This allows us to calculate the rain-out of HCN into warm little ponds (WLPs). We then use a comprehensive numerical model of sources and sinks to compute the resulting abundances of nucleobases, ribose, and nucleotide precursors such as 2-aminooxazole resulting from aqueous and UV-driven chemistry within them. We find that 4.4 billion years ago the limit of adenine concentrations in ponds for habitable surfaces is 0.05 μM in the absence of seepage. Meteorite delivery of adenine to WLPs can provide boosts in concentration by 2–3 orders of magnitude, but these boosts deplete within months by UV photodissociation, seepage, and hydrolysis. The early evolution of the atmosphere is dominated by the decrease in hydrogen due to falling impact rates and atmospheric escape, and the rise of oxygenated species such as OH from H2O photolysis. The source of HCN is predominantly from UV radiation rather than lightning. Our work points to an early origin of RNA on Earth within ∼200 Myr of the Moon-forming impact.

Laboratory spectroscopy of allylimine and tentative detection towards the G+0.693-0.027 molecular cloud

“…Life could have emerged starting from precursors of biomolecular building blocks synthesised in situ, during our planet's cooling. Successive RNA polymerization could have then emerged in warm little ponds as a result of condensation of lightning synthesised abiotic precursors (Pearce et al 2022), produced in a Urey-Miller experiment fashion (Miller 1953). Another hypothesis is that prebiotic compounds might have had an extraterrestrial origin.…”

A High-resolution Spectroscopic Analysis of Aminoacrylonitrile and an Interstellar Search toward G+0.693

“…Life could have emerged starting from precursors of biomolecular building blocks synthesized in situ, during our planet's cooling. Successive RNA polymerization could have then emerged in warm little ponds as a result of condensation of lightning synthesized abiotic precursors (Pearce et al 2022), produced in a Urey-Miller experiment fashion (Miller 1953). Another hypothesis is that prebiotic compounds might have had an extraterrestrial origin.…”

Ammonium affects the wet chemical network of HCN: feedback between prebiotic chemistry and materials science

“…12 HCN is an abundant molecule throughout the universe. HCN polymers have long been proposed as the oldest and most stable organic macromolecules in the solar system 13,14 and they have been related to dark matter found within asteroids a Centro de Astrobiologı ´a (CAB), INTA-CSIC, Ctra. Torrejo ´n-Ajalvir, km 4, Torrejo ´n de Ardoz, 28850 Madrid, Spain.…”

“…15 In addition, it was proposed that HCN is a key compound in the chemical evolution processes that led to life. 14,[16][17][18][19] On the other hand, due to the constraints of prebiotic chemistry, only water is used as a solvent in the simulation of abiotic scenarios. Thus, the aqueous syntheses of HCN-derived polymers have been largely performed using net HCN, its soluble salts (NaCN and KCN), its formal trimers or its tetramers (aminomalononitrile, AMN, and diaminomaleonitrile, DAMN) in a very broad range of temperatures (from À78 1C to 205 1C) 12,[20][21][22] and even its hydrolysis products, such as formamide.…”

“…12 HCN is an abundant molecule throughout the universe. HCN polymers have long been proposed as the oldest and most stable organic macromolecules in the solar system 13,14 and they have been related to dark matter found within asteroids and comets. 15 In addition, it was proposed that HCN is a key compound in the chemical evolution processes that led to life.…”