The rise of exoplanet science and discovery of new temperate worlds open up a new avenue in the search for the origin of life. Pioneering laboratory studies have shown that ultraviolet (UV) radiation plays a major role for abiogenesis (e.g. Powner et al., 2009; Patel et al., 2015; Xu et al, 2018; Rimmer et al., 2018). But do the mechanisms working in a laboratory, and proposed to work on a young Earth, also work in more extreme environments? Can the same chemistry take place on worlds with thin atmospheres, low magnetic fields and stars more active and ‘chaotic’ than our Sun? And do low gravity environments (like on our Moon) affect the mixing and reaction rates, accelerating or decelerating the chemistry?
Here, we propose to take these experiments to the next step, and prepare for prebiotic chemistry studies in extreme regimes. While the Sun delivers a relatively constant UV flux to Earth, the situation is very different for most temperate exoplanets. Many orbit small and cool red dwarf stars, which have a major caveat for habitability: they emit far less quiescent UV radiation than our Sun, but frequently undergo explosive stellar eruptions (‘flares’). Thus, these exoplanets face sudden spikes in charged particle fluxes and UV light (e.g. Günther et al, 2019). Additionally, Earth's atmosphere and magnetic field protect us from most harming particles and radiation - but might be different for exoplanets.
To test this prebiotic chemistry in more exposed environments, the first step is making the set-ups space-proof and elevating them into the outer layers of our Earth's atmosphere. By developing the experiments to work in a Zero-G flight environment, we can gather all necessary expertise towards this goal. In the intermediate future, this can lead to extended tests in space/sub-orbital flights and later on the International Space Station. In the long term, the experiments could be set up on the Moon and on Mars. Their surfaces are less protected from solar flares than Earth's, and their gravitational environments might alter the mixing and reaction rates of the experiments. Ultimately, by measuring the impact of these different environments, we will unveil if this chemistry could have taken place on any 'habitable exoplanet' candidates.
In practice, we will develop a robust, compact, and simplified version of the setup in Rimmer et al., 2018, to experimentally measure the rate constant for the light chemistry involving bisulfite,
SO32− , versus the rate constants in the absence of light (see their Fig. 1). We will be able to compare the rate constants measured in the zero gravity environment (experiencing turbulence and different mixing ratios) with the ones measured in the previous laboratory studies.
References and links:
Powner et al., 2009: https://www.nature.com/articles/nature08013
Patel et al., 2015: https://www.ncbi.nlm.nih.gov/pubmed/25803468
Xu et al., 2018: https://pubs.rsc.org/en/content/articlelanding/2018/cc/c8cc01499j#!divAbstract Rimmer et al., 2018: https://advances.sciencemag.org/content/4/8/eaar3302
Günther et al, 2019: https://arxiv.org/abs/1901.00443