Comparative planetology, climatology and biology of Venus, Earth and Mars

Spacecraft studies of the three terrestrial planets with atmospheres have made it possible to make meaningful comparisons that shed light on their common origin and divergent evolutionary paths. Early in their histories, all three apparently had oceans and extensive volcanism; Mars and Earth, at least, had magnetic fields, and Earth, at least, had life. All three currently have climates determined by energy balance relationships involving carbon dioxide, water and aerosols, regulated by solar energy deposition, atmospheric and ocean circulation, composition, and cloud physics and chemistry.This paper addresses the extent to which current knowledge allows us to explain the observed state of each planet, its planetology, climatology and biology, within a common framework. Areas of ignorance and mysteries are explored, and prospects for advances in resolving these with missions within the present planning horizon of the space agencies are considered and assessed.

Research Highlights► It is an introductory overview for the International Conference on Comparative Planetology. ► The common origin and divergent evolutionary paths of terrestrial planet atmospheres are described. ► The roles of oceans and volcanism, magnetic fields, and life in climate are considered. ► Each planet, its planetology, climatology and biology, within a common framework is addressed. ► Areas of ignorance and mysteries are explored, and prospects for advances with planned missions are considered.