The Emergence of Habitable Conditions in the Solar System

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.

Our impact plan offers a number of different paths to implementation that involves industry and community engagement and outreach. Key activities in the framework of this grant are:

Industrial links
Date driven innovation and space and satellite development. Snodgrass was hired alongside a cohort of 30 academics across all disciplines in the university as part of a major investment in 'Data Driven Innovation' (DDI) in Edinburgh, bringing together the university and the city region with the express intention of turning Edinburgh into the 'data capital of Europe'. Snodgrass is one of three DDI fellows within the 'space and satellites' theme; his work in developing spacecraft mission concepts directly informs collaboration with companies developing new satellite technology. Via the development of the Comet Interceptor mission, and particularly its CubeSat-scale deployable probes, the projects described here will inform innovation and technology development in start-up companies.

Instrument development
Our applicants are involved in diverse projects with implications for planetary sciences instrument development. Our work on space biology (Theme 3) provides research knowledge that informs the development of space hardware development. The bioreactors that we developed with Kayser Italia that we flew in the BioRock experiment have potential for use in autonomous space experiments on other orbital platforms and the Moon. We are currently engaged in a collaboration with Kayser Space Ltd to consider how to modify the hardware for autonomous operation. Our research informs science related to instruments being developed for planetary missions. For example, our study of aqueous environments (Themes 2 and 4) informs the interpretation of data sent back by the instruments on the ExoMars 2020 and other planetary missions. This grant would not fund or support involvement in instrument development as they fall in the domain of the UK Space Agency, but the scientific work carried out informs our scientific knowledge, which increases the efficacy of our scientific contribution to planetary missions.

Community engagement and outreach
Our applicants take an active role in applying their expertise and research to advancing community outreach and education. One example of such efforts, which used the research and expertise of our previous consolidated grant, and will be continued in the lifetime of this grant, is Life Beyond. This is a programme to take astrobiology into the prison environment in a collaboration with the Scottish Prison Service (SPS). In this programme, inmates lead a design for a station on another planetary surface. They engage in science, literacy, design, art and creative writing. The material they produce is published as a book in collaboration with the British Interplanetary Society (BIS), e.g. Life Beyond: From Prison to Mars. Our programme was recently included in examples of best practice in prison education by EuroPris, a EU Europe-wide prison education collaboration.
Another example of community engagement is our work with the Scottish government's RAISE (Raising Aspirations in Science Education) programme. In the last two years, material developed through our Astrobiology Summer Academy has been modified in collaboration with the Scottish government for use in primary to secondary transition as part of RAISE. In 2018, 51 teachers and practitioners were trained in using the astrobiology materials across five school clusters across Scotland, reaching over 1,000 pupils. The material is now part of the National Resource Guide and the National Education Portal and is being expanded to new clusters and groups across Scotland.

Members of our grant give lectures in public forums, providing another mechanism by which our work is widely disseminated. These contributions have included lectures at the Edinburgh International Festival, local schools and public outreach events, astronomy societies etc.