III. Ecosmos: A Revolutionary Fertile, Habitable, Solar-Bioplanet, Incubator Lifescape

G. An Astrochemistry to Astrobiological Spontaneity

Seager, Sara, et al. Toward a List of Molecules as Potential Biosignature Gases for the Search for Life on Exoplanets and Applications to Terrestrial Biochemistry. Astrobiology. 16/6, 2016. As a sign of the rapid progress being made by an instant global community, MIT scientists now move on from detecting exoworld atmospheres (the very idea that we Earthlings can do this all is incredible and auspicious) to assessments by virtue of organic traces whether it harbors organic life. As a guideline, a long inventory of our own Gaian biochemical components is listed. For another aspect, see Chemical Complementarity between the Gas Phase of the Interstellar Medium and the Rocky Material of Our Planetary System by Haiyang Wang and Charles Lineweaver at arXiv:1605.05503.

Thousands of exoplanets are known to orbit nearby stars. Plans for the next generation of space-based and ground-based telescopes are fueling the anticipation that a precious few habitable planets can be identified in the coming decade. Even more highly anticipated is the chance to find signs of life on these habitable planets by way of biosignature gases. But which gases should we search for? Although a few biosignature gases are prominent in Earth's atmospheric spectrum (O2, CH4, N2O), others have been considered as being produced at or able to accumulate to higher levels on exo-Earths (e.g., dimethyl sulfide and CH3Cl). Life on Earth produces thousands of different gases (although most in very small quantities). Some might be produced and/or accumulate in an exo-Earth atmosphere to high levels, depending on the exo-Earth ecology and surface and atmospheric chemistry.

To maximize our chances of recognizing biosignature gases, we promote the concept that all stable and potentially volatile molecules should initially be considered as viable biosignature gases. We present a new approach to the subject of biosignature gases by systematically constructing lists of volatile molecules in different categories. An exhaustive list up to six non-H atoms is presented, totaling about 14,000 molecules. About 2500 of these are CNOPSH compounds. An approach for extending the list to larger molecules is described. We further show that about one-fourth of CNOPSH molecules (again, up to N = 6 non-H atoms) are known to be produced by life on Earth. The list can be used to study classes of chemicals that might be potential biosignature gases, considering their accumulation and possible false positives on exoplanets with atmospheres and surface environments different from Earth's. The list can also be used for terrestrial biochemistry applications, some examples of which are provided. We provide an online community usage database to serve as a registry for volatile molecules including biogenic compounds. (Abstract)

Sephton, Mark. Organic Matter in Ancient Meteorites. Astronomy & Geophysics. 45/2, 2004. These nutrient fragments serve as cosmic time capsules which reveal early chemical steps toward life. They contain biological molecules of extraterrestrial origin that help fill in the course of complexifying animate matter.

Smith, Ian. Reactions at Very Low Temperatures. Angewandte Chimie. 45/18, 2006. A survey of the latest research in astrochemistry – the search for complex molecules in the interstellar reaches – which has now found over 135 biochemical precursors.

Smith, Ian, et al, eds. Astrochemistry and Astrobiology. Berlin: Springer, 2013. With coeditors Charles Cockell and Sydney Leach, an initial volume in a “Physical Chemistry in Action” series. A stellar cast of active scientists proceed to root and connect living beings ever more deeply in and continuous with an increasingly conducive, animate matter. Chapters run from “The Molecular Universe” by Maryvonne Gerin, “Planetary Atmospheres and Chemical Markers for Extraterrestrial Life,” Lisa Kaltenegger, onto “Life, Metabolism and Energy,” Robert Pascal and “The Physical Underpinnings of Replication” by Rebecca Turk-MacLeod, Ulrich Gerland, and Irene Chen. For effect, we join this volume with a concurrent December 2012 issue of Accounts of Chemical Research on “Origins of Chemical Evolution.” In our midst, so far unbeknownst, an innately fertile genesis universe is becoming revealed as a credible discovery, indeed a cosmic Copernican revolution.

The origin of life was a special point in our history when the principles of physics and chemistry first blossomed into the complex interactions that characterize living organisms. Biological phenomena, like replication, can be thought of as emerging from deeper microscopic structural and dynamic properties, in the same way that the physical phenomenon of friction emerges from microscopic interactions among materials. Although living organisms today are often so sophisticated that it can be difficult to see the roots of physical chemistry in their everyday operation, the very first organisms and transitional form would have been quite close to those roots. (Turk-MacLeod, 271)

Snyder, Lewis. Interferometric Observations of Large Biologically Interesting Interstellar and Cometary Molecules. Proceedings of the National Academy of Science. 103/12243, 2006. An example of our collaborative ability to explore and find an organic universe with a natural propensity to form precursors of complex, evolving life. The paper by William Klemperer, Interstellar Chemistry, in the same issue is also notable.

Interferometric observations of high-mass regions in interstellar molecular clouds have revealed hot molecular cores that have substantial column densities of large, partly hydrogen-saturated molecules. Many of these molecules are of interest to biology and thus are labeled “biomolecules.” Because the clouds containing these molecules provide the material for star formation, they may provide insight into presolar nebular chemistry, and the biomolecules may provide information about the potential for the associated interstellar chemistry for seeding newly formed planets with prebiotic organic chemistry. (12243)

Sole, Ricard and Andreea Munteanu. The Large-Scale Organization of Chemical Reaction Networks in Astrophysics. Europhysics Letters. 68/2, 2004. As a self-regulated biosphere, earth’s far-from-equilibrium atmosphere exhibits a scale-free, modular, hierarchical topology similar to cellular metabolic networks. For chemicals found in the interstellar medium, a simpler reaction graph structure holds. These two basic types of networks can then be associated with the presence or absence of extrasolar planetary life.

Taniguchi, Kotomi, et al. Carbon-Chain Chemistry in the Interstellar Medium.. arXiv:2303.15769. Some fifty years after their first notice, National Astronomical Observatory of Japan and Chalmers University of Technology, Sweden review the ever-growing organic presence of such life-bearing biochemicals across the galactic realms. A half century on, it has become increasingly evident and persuasive that a fertile ecosmic conducive milieu indeed has a phenomenal existence.

The presence of carbon-chain molecules in the interstellar and galactic medium has been known since the 1970s and over 100 such species have been identified to date. They provide vital information on physical conditions, gas dynamics, and evolutionary stages of star-forming regions. More complex species of polycyclic aromatic hydrocarbons and fullerenes have been detected in circumstellar envelopes around carbon-rich Asymptotic Giant Branch stars and planetary nebulae. This article updates carbon-chain molecules via observational studies, chemical simulations, quantum calculations, and laboratory experiments. (Excerpt)

Ulmschneider, Peter. Intelligent Life in the Universe. Berlin: Springer, 2003. A recent review set within a Darwinian frame but whose perspective allows cosmic and earthly evolution to be distinguished by ‘a long-range direction’ of the growth of information.

Vakoch, Douglas and Matthew Dowd, eds. The Drake Equation: Estimating the Prevalence of Extraterrestrial Life through the Ages. Cambridge: Cambridge University Press, 2015. The collection is a 2010s retrospective and update of astronomer Frank Drake’s (who at 85 writes a Foreword) 1961 attempt to estimate the probability of extraterrestrial civilizations. As an equation, it involves seven aspects: the rate of galactic star formation, how many suns have planets, the number of orbital worlds, how many are then habitable, then bearing intelligent life, onto communicative civilizations, and finally their relative lifetime. The book proceeds with chapters which consider both pre-1960 versions, and what has been learned since for each component. Of course the 21st century breakthrough discoveries of prolific orbital planets factors largely. Historian Steven Dick introduces, while e.g., Chris Impey views solar systems, David Des Marais on the likelihood of life, and Seth Shostak aptly looks at the detection of signals. The chapter Fraction of Life-Bearing Planets on Which Intelligent Life Emerges, fi, 1961 to the Present by ethnologist Lori Marino is reviewed separately.

Vakoch, Douglas, ed. Communication with Extraterrestrial Intelligence. Albany: State University of New York Press, 2011. Wherein leading advocates such as Jull Tarter, Seth Shostak, Samantha Blair, Frank Drake, Kathryn Denning, and many others entertain celestial visions from exoplanets to an intergalactic Rosetta language. A typical paper might be “Pragmatism, Cosmocentrism, and Proportional consultation for CETI” by Marc Lupisella.

In April 2010, fifty years to the month after the first experiment in the Search for Extraterrestrial Intelligence (SETI), scholars from a range of disciplines--including astronomy, mathematics, anthropology, history, and cognitive science--gathered at NASA's biennial Astrobiology Science Conference (AbSciCon) for a series of sessions on the search for intelligent life. This book highlights the most recent developments in SETI discussed at that conference, emphasizing the ways that SETI has grown since its inception. The volume covers three broad themes: First, leading researchers examine the latest developments in observational SETI programs, as well as innovative proposals for new search strategies and novel approaches to signal processing. Second, both proponents and opponents of "Active SETI" debate whether humankind should be transmitting intentional signals to other possible civilizations, rather than only listening. Third, constructive proposals for interstellar messages are juxtaposed with critiques that ask whether any meaningful exchange is possible with an independently evolved civilization, given the constraints of contact at interstellar distances, where a round-trip exchange could take centuries or millennia. (Publisher)

Van Dischoeck, Ewine. Astrochemistry of Dust, Ice and Gas. Faraday Discussions.. 168/9, 2014. Online at arXiv:1411.5280, the Leiden University and MPI Extraterrestrial Physics researcher describes a celestial expanse which by its innate nature appears as a fertile milieu for organic life and evolution. See also Water: From Clouds to Planets by Ewine van Dishoeck, et al at arXiv:1401.8103.

A brief introduction and overview of the astrochemistry of dust, ice and gas and their interplay is presented, aimed at non-specialists. The importance of basic chemical physics studies of critical reactions is illustrated through a number of recent examples. Such studies have also triggered new insight into chemistry, illustrating how astronomy and chemistry can enhance each other. Much of the chemistry in star- and planet-forming regions is now thought to be driven by gas-grain chemistry rather than pure gas-phase chemistry, and a critical discussion of the state of such models is given. Recent developments in studies of diffuse clouds and PDRs, cold dense clouds, hot cores, protoplanetary disks and exoplanetary atmospheres are summarized, both for simple and more complex molecules, with links to papers presented in this volume. In spite of many lingering uncertainties, the future of astrochemistry is bright: new observational facilities promise major advances in our understanding of the journey of gas, ice and dust from clouds to planets. (Abstract)

Van Dishoeck, Ewine. Astrochemistry: Overview and Challenges. arXiv:1710.05940. The Leiden Observatory professor of molecular astrophysics is also president-elect of the International Astronomical Union. This posting surveys the robust confirmation of an interstellar and extragalactic medium that seems to innately form and seed itself with increasingly complex chemicals and bioprecursors. Might one muse that they are just the materials that planets need to form and life to evolve so we peoples might achieve their intelligent description? It is to appear as a chapter in IAU Symposium 332: Astrochemistry VII: Through the Cosmos from Galaxies to Planets (2018). See also The Diverse Chemistry of Protoplanetary Disks as
Revealed by the JWST by Ewine van Dishoeck, et al at 2307.11817 for a review six years later.

This paper provides a brief overview of the journey of molecules through the Cosmos, from local diffuse interstellar clouds and PDRs to distant galaxies, and from cold dark clouds to hot star-forming cores, protoplanetary disks, planetesimals and exoplanets. Recent developments in each area are sketched and the importance of connecting astronomy with chemistry and other disciplines is emphasized. Fourteen challenges for the field of Astrochemistry in the coming decades are formulated. (Abstract)

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