Polymerization of Building Blocks of Life on Europa and Other 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.

The habitability of planets orbiting M-dwarf stars

“…Experiments investigating the tolerance of Earth organisms to extreme conditions have been carried out with an eye toward an application to the environments of the early Earth (Cnossen et al, 2007;Westall et al, 2011;Grosch & Hazen, 2015), solar system planets like Mars (Navarro-González et al, 2003;Cockell & Raven, 2004;Diaz & Schulze-Makuch, 2006;de la Vega et al, 2007;Dartnell et al, 2010), the moons of the outer solar system such as Jupiter's moon Europa (Chyba, 2000;Chyba & Phillips, 2002;Deming, 2002;Marion et al, 2003;Bulat et al, 2004Bulat et al, , 2011Kimura & Kitadai, 2015;Noell et al, 2015), and interplanetary space (Paulino-Lima et al, 2010). However, given the varied factors that may influence the climate and surface environment of M-dwarf planets, much of what has been learned about the mechanisms employed by extremophilic life on Earth to not only survive but thrive has implications for the likelihood of life to grow and evolve on planets in close-in orbits around these small, cool stars.…”

Living at the Extremes: Extremophiles and the Limits of Life in a Planetary Context

“…McCord and Castillo-Rogez, 2018; McCord and Zambon, 2019; Neveu and Desch, 2015;Villarreal et al, 2017;Vu et al, 2017;Zolotov, 2009 Ion sputtering of the surface; potential water plumes ; O2; trace amounts of sodium and potassium Cassidy et al, 2013;Chyba and Phillips, 2001;Hand and Carlson, 2015;Jones et al, 2018;Kattenhorn and Prockter, 2014;Kimura and Kitadai, 2015;Marion et al, 2005;Martin and McMinn, 2018;McGrath et al, 2009;Muñoz-Iglesias et al, 2013;Noell et al, 2015;Pavlov et al, 2018;Soderlund et al, 2014;Spencer et al, 1999;Teolis et al, 2017;Travis et al, 2012;Vance et al, 2016;Zolotov and Kargel, 2009 Surface (icy shell) -187 --141 nr 0. Potential for wide range q 0.1 -30 r <3.5 Likely contains Mg 2+ , SO4 2-, Na + , Cl -; oxidants and simple organics a -Thermosphere can be as cold as -173ºC (Bertaux et al, 2007); the upper-to-middle cloud layers are between -40-60ºC (Cockell, 1999) b -Acid concentration in upper cloud layer is 81%, in lower layers up to 98% (Cockell, 1999) c -Up to 11 MPa in a deep depression (Basilevsky and Head, 2003) d -Summer air temperatures on Mars near the equator can reach a maximum of 35ºC (Longstaff, 2014) e -Measured by the Phoenix Mars Lander Wet Chemistry Laboratory at the northern plains of the Vastitas Borealis (Hecht et al, 2009) f -Liquid water may have had water activity > 0.95 (Fairén et al, 2009) g -Calculated temperature at a depth of 1-30 km (Sinha2017, Jones2011); at a depth ~310 km, the calculated temperature is <427ºC (Jones 2011); the Martian core has temperature 1527ºC…”

Can Life Begin on Enceladus? A Perspective from Hydrothermal Chemistry

“…Kimura and Kitadai ( 2015 ) performed a theoretical analysis of the free energy available to drive peptide condensation reactions at the very low surface temperatures of Europa. They concluded that at temperatures below 118 K, the Gibbs energy becomes negative, which means, for instance, that diglycine can be synthesized from glycine on Europa and other icy moons.…”