Editorial: Astrobiology of Mars, Europa, Titan and Enceladus - Most Likely Places for Alien Life

A primary science goal of astrobiology is to understand the biological potential of Solar System bodies. Looking beyond Earth, four planetary bodies, namely Mars, Europa, Titan and Enceladus, offer numerous opportunities to investigate the chemical evolution and origin of life. These bodies may have biochemistry similar to that of life on Earth (Davila and McKay, 2014; Taubner et al., 2018; Taubner et al., 2020). In recent years, exploration strategies have been developed to pursue astrobiological objectives for these targets. Two key scientific objectives of current and planned space missions to these bodies are 1) to investigate the abundance and distribution of the organic compounds and biomolecules, as well as environmental conditions (causing alteration, degradation and even complete destruction of these compounds such as irradiation, mineralogy etc.), as these are crucial in the search of biosignatures; and 2) to identify evidence of ancient biota and to determine whether indigenous organisms currently exist anywhere on the surface and subsurface of these planetary bodies.