The Emergence of Habitable Conditions in the Solar System

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How do solar systems emerge from the violence of the protoplanetary disc to be habitable environments for life? Although there is much focus on the present-day habitability of bodies in our Solar System, there is remarkably little understanding of how Solar System bodies have evolved over time and what the starting conditions were that led to potentially habitable aqueous environments. We can only really assess whether habitable conditions might be common in the Universe (one key objective of STFC's science priorities) if we understand the factors that canalise a Solar System towards or away from habitable conditions. This is the fundamental aim of the work we propose here.One major challenge is understanding the volatile inventory of the early Solar System and what volatiles were available in early Solar System bodies that could have led to habitable aqueous environments. To address this problem we need to have a better grasp of the composition of early Solar System materials. One enormously important class of such bodies is comets. In this work, we will significantly advance our understanding of the taxonomy and composition of comets. Although comets are not the only providers of volatiles in the early Solar System, they provide key insights into the materials from which solar systems are made and that define the boundary conditions for early volatiles and potential fluids. Once these volatiles coalesced into planetary bodies, they led to the many aqueous environments we observe in the Solar System today (early Mars, Europa, Enceladus, even asteroids such as Ceres). However, how have these aqueous environments evolved. What happens when solutions of early volatiles freeze and what solutions result? How do key volatiles, such as ammonia, which depress the freezing point, alter these solutions? Most crucially, how does habitability alter in these evolving fluids? We will address these questions by linking planetary sciences with astrobiology (microbiology) to investigate and advance our understanding of how the habitability of early Solar System solutions have evolved over time.An unseen elephant in the room in terms of planetary habitability is gravity. It is pervasive in all environments, even if its influence is caused by its near absence. Using our heritage of flying space experiments, we will use equipment we have developed for spaceflight to study the growth of organisms on primitive asteroidal material (chondritic material) in the BioAsteroid experiment on the International Space Station. Comparisons with data gathered in our previous BioRock experiment using basalt will allow us to investigate the growth and habitability of early Solar System bodies and materials and, in particular, the habitability of chondritic small Solar System bodies under low gravity regimes. This work will give us important new insights into the role of gravity in defining the habitability of solar system bodies.STFC has a scientific priority to find out if life is unique to Earth, but to eventually look for life in habitable environments, we have to be able to distinguish it from non-life. Chemical processes are known to generate pseudo-biosignatures - morphologies and chemical signatures that look like life. Yet we know very little about how early Solar System environments, such as in icy moons and early Mars, might have generated false signatures of life. Understanding how early solar systems might generate signatures of life-like materials is essential if we are to avoid being misled into thinking we have found life. We will significantly advance our understanding of the ability of the early Solar System to produce such pseudo-biosignatures.In summary, our proposed projects fit together into a coherent and systematic programme of study to understand how the early Solar System evolved into habitable conditions and how we might reliably seek signatures of life within habitable planetary environments.