Polymerization of building blocks of life on Europa and other icy moons

TL;DR

This paper explores the potential for organic monomers like amino acids and nucleotides to polymerize spontaneously on icy moons such as Europa, suggesting a possible pathway for prebiotic chemistry in extraterrestrial environments based on thermodynamic calculations.

Contribution

It demonstrates, through thermodynamic analysis, that polymerization of organic molecules could occur on Europa's surface despite low temperatures, providing new insights into prebiotic chemistry in icy moon environments.

Findings

Polymerization of amino acids and nucleotides is thermodynamically favorable at Europa's surface temperatures.

A shallow subsurface region on Europa could support organic polymerization.

Thermodynamic conditions suggest potential for prebiotic chemistry on icy moons.

Abstract

The outer solar system may provide a potential habitat for extraterrestrial life. Remote sensing data from the Galileo spacecraft suggest that the jovian icy moons, Europa, Ganymede, and possibly Callisto, may harbor liquid water oceans underneath their icy crusts. Although compositional information required for the discussion of habitability is limited because of significantly restricted observation data, organic molecules are ubiquitous in the universe. Recently, in-situ spacecraft measurements and experiments suggest that amino acids can be formed abiotically on interstellar ices and comets. These amino acids could be continuously delivered by meteorite or comet impacts to icy moons. Here, we show that polymerization of organic monomers, in particular amino acids and nucleotides, could proceed spontaneously in the cold environment of icy moons, in particular the Jovian icy moon Europa as a typical example, based on thermodynamic calculations, though kinetics of formation are not addressed. Observed surface temperature on Europa is 120 and 80 K in the equatorial region and polar region, respectively. At such low temperatures, Gibbs energies of polymerization become negative, and the estimated thermal structure of the icy crust should contain a shallow region (i.e., at a depth of only a few kilometers) favorable for polymerization. Investigation of the possibility of organic monomer polymerization on icy moons could provide good constraints on the origin and early evolution of extraterrestrial life.