An objective Bayesian analysis of life's early start and our late arrival

A Bayesian Analysis of the Probability of the Origin of Life Per Site Conducive to Abiogenesis

The emergence of life from nonlife, or abiogenesis, remains a fundamental question in scientific inquiry. In this article, we investigate the probability of the origin of life (per conducive site) by leveraging insights from Earth's environments. If life originated endogenously on Earth, its existence is indeed endowed with informative value, although the interpretation of the attendant significance hinges critically upon prior assumptions. By adopting a Bayesian framework, for an agnostic prior, we establish a direct connection between the number of potential locations for abiogenesis on Earth and the probability of life's emergence per site. Our findings suggest that constraints on the availability of suitable environments for the origin(s) of life on Earth may offer valuable insights into the probability of abiogenesis and the frequency of life in the universe.

Potassium at the Origins of Life: Did Biology Emerge from Biotite in Micaceous Clay?

Intracellular potassium concentrations, [K+], are high in all types of living cells, but the origins of this K+ are unknown. The simplest hypothesis is that life emerged in an environment that was high in K+. One such environment is the spaces between the sheets of the clay mineral mica. The best mica for life’s origins is the black mica, biotite, because it has a high content of Mg++ and because it has iron in various oxidation states. Life also has many of the characteristics of the environment between mica sheets, giving further support for the possibility that mica was the substrate on and within which life emerged. Here, a scenario for life’s origins is presented, in which the necessary processes and components for life arise in niches between mica sheets; vesicle membranes encapsulate these processes and components; the resulting vesicles fuse, forming protocells; and eventually, all of the necessary components and processes are encapsulated within individual cells, some of which survive to seed the early Earth with life. This paper presents three new foci for the hypothesis of life’s origins between mica sheets: (1) that potassium is essential for life’s origins on Earth; (2) that biotite mica has advantages over muscovite mica; and (3) that micaceous clay is a better environment than isolated mica for life’s origins.

Formulation and resolutions of the red sky paradox

Most stars in the Universe are red dwarfs. They outnumber stars like our Sun by a factor of 5 and outlive them by another factor of 20 (population-weighted mean). When combined with recent observations uncovering an abundance of temperate, rocky planets around these diminutive stars, we are faced with an apparent logical contradiction-Why do we not see a red dwarf in our sky? To address this "red sky paradox," we formulate a Bayesian probability function concerning the odds of finding oneself around an F/G/K-spectral type (Sun-like) star. If the development of intelligent life from prebiotic chemistry is a universally rapid and ensured process, the temporal advantage of red dwarfs dissolves, softening the red sky paradox, but exacerbating the classic Fermi paradox. Otherwise, we find that humanity appears to be a 1-in-100 outlier. While this could be random chance (resolution I), we outline three other nonmutually exclusive resolutions (II to IV) that broadly act as filters to attenuate the suitability of red dwarfs for complex life. Future observations may be able to provide support for some of these. Notably, if surveys reveal a paucity of temperate rocky planets around the smallest (and most numerous) red dwarfs, then this would support resolution II. As another example, if future characterization efforts were to find that red dwarf worlds have limited windows for complex life due to stellar evolution, this would support resolution III. Solving this paradox would reveal guidance for the targeting of future remote life sensing experiments and the limits of life in the cosmos.

A Statistical Estimation of the Occurrence of Extraterrestrial Intelligence in the Milky Way Galaxy

In the field of astrobiology, the precise location, prevalence, and age of potential extraterrestrial intelligence (ETI) have not been explicitly explored. Here, we address these inquiries using an empirical galactic simulation model to analyze the spatial–temporal variations and the prevalence of potential ETI within the Galaxy. This model estimates the occurrence of ETI, providing guidance on where to look for intelligent life in the Search for ETI (SETI) with a set of criteria, including well-established astrophysical properties of the Milky Way. Further, typically overlooked factors such as the process of abiogenesis, different evolutionary timescales, and potential self-annihilation are incorporated to explore the growth propensity of ETI. We examine three major parameters: (1) the likelihood rate of abiogenesis (λA); (2) evolutionary timescales (Tevo); and (3) probability of self-annihilation of complex life (Pann). We found Pann to be the most influential parameter determining the quantity and age of galactic intelligent life. Our model simulation also identified a peak location for ETI at an annular region approximately 4 kpc from the galactic center around 8 billion years (Gyrs), with complex life decreasing temporally and spatially from the peak point, asserting a high likelihood of intelligent life in the galactic inner disk. The simulated age distributions also suggest that most of the intelligent life in our galaxy are young, thus making observation or detection difficult.