Electrostatic activation of prebiotic chemistry in substellar atmospheres

Abstract

Charged dust grains in the atmospheres of exoplanets may play a key role in the formation of prebiotic molecules, necessary to the origin of life. Dust grains submerged in an atmospheric plasma become negatively charged and attract a flux of ions that are accelerated from the plasma. The energy of the ions upon reaching the grain surface may be sufficient to overcome the activation energy of particular chemical reactions that would be unattainable via ion and neutral bombardment from classical, thermal excitation. As a result, prebiotic molecules or their precursors could be synthesized on the surface of dust grains that form clouds in exoplanetary atmospheres. This paper investigates the energization of the plasma ions, and the dependence on the plasma electron temperature, in the atmospheres of substellar objects such as gas giant planets. Calculations show that modest electron temperatures of &1 eV (& 10 4 K) are enough to accelerate ions to sufficient energies that exceed the activation energies required for the formation of formaldehyde, ammonia, hydrogen cyanide and the amino acid glycine.

Evaluating galactic habitability using high-resolution cosmological simulations of galaxy formation

“…One could imagine circumstances where planetary systems in regions of enhanced dust density are afforded a shield against ionizing radiation and cosmic rays. Equally, this biohazardous radiation may become biogenic radiation if it encounters dust/gas mixtures amenable to grain surface chemistry, enhancing the production of organic molecules and potentially even prebiotics (Hill & Nuth 2003; Stark et al 2014). This will have significant effects on the calculated habitability of low density regions such as tidal streams and the outer edges of satellite galaxies, and shows that a fully matured GHZ calculation must account for the anisotropy of radiative feedback as it encounters asymmetric distributions of intervening material.…”

Exoplanetary Atmospheres—Chemistry, Formation Conditions, and Habitability

“…Rimmer and Helling (2013) and Rimmer et al (2014) have explored the effects of cosmic rays on the atmospheric compositions of extrasolar giants planets. Charging of mineral grains, and potential subsequent electrical discharges, are another possible source of disequilibrium chemistry on extrasolar giant planets (see Helling et al 2013; Bailey et al 2014; Stark et al 2014).…”

Modelling the local and global cloud formation on HD 189733b

“…This leaves open the possibility of lightning discharge events in exo-clouds (Bailey et al 2014). Furthermore, Stark et al (2014) suggest that charged dust grains could aid the synthesis of prebiotic molecules by enabling the required energies of formation on their surfaces. Multi-dimensional atmosphere simulations have been used to gain a first insight into the atmospheric dynamics of HD 189733b (e.g.…”