III. Ecosmos: A Revolutionary Fertile, Habitable, Solar-Bioplanet Incubator Lifescape
I. Our EarthMost Occasion: A Rarest Confluence of Favorable Features and Close Calls
Ambrifi, Alessandro, et al. The Impact of AGN Outflows on the Surface Habitability of Terrestrial Planets in the Milky Way. arXiv:2203.00929. Into 2022 Vergata University of Rome and Florida Institute of Technology exophysicists including Arnedeo Balbi and Manasvi Lingam can quantify and report how such energetic emissions across the parsecs could be another factor which can influence living, evolutionary systems.
Active galactic nuclei (AGN) are accompanied by winds and emission which may reach 10 percent the speed of light. Here, we describe how AGN winds can heat atmospheres and drive their escape, which forms nitrogen oxides which cause ozone depletion. Our models estimate the maximal distance to which these deleterious effects are rendered significant for Earth-like planets, and show that this value may extend to ≲1 kpc. In the case of quasars hosting larger supermassive black holes, such effects could actually influence the AGN host galaxy as a whole. (Abstract excerpt)
Anand, Rajagopal. Orbital Properties and Implications for the Initiation of Plate Tectonics and Planetary Habitability. arXiv:2202.10719. new findings pour in, an Indian Institute of Technology astrogeologist can look more deeply into our Earth life occasion and realize the vital role played by mobile plate tectonics. Thus another key factor is added to an extent that the paper closes with an Earth, the Unique Planet title.
The existence of plate tectonics on the Earth is directly dependent on the internal viscosity contrast, mass of the planet, availability of liquid water and an internal heat source. However, the initial and long term optimum conditions of rotational velocity and periodicity of the Earth’s orbit around the Sun must also have been significant for the inception of plate tectonics. Such an optimal condition for the rotational and revolutionary periodicities could be essential for the development of plate tectonics on the Earth. (Abstract excerpt)
Angier, Natalie. The Earth’s Shell has Cracked, and We’re Drifting on the Pieces. New York Times. December 18, 2018. The popular science writer draws upon a Royal Society meeting about plate tectonics and Philosophical Transactions A issue from it (see Robert Stern herein for more) about how our home planet has been distinguished and enlivened by mobile continental forms over a billion years, while Venus and many other worlds have not. It is noted that this ancient surface balance of land and sea is vitally crucial for a planet to become habitable for life and evolution. She consulted with R. Stern (UT Dallas), Jun Korenaga (Yale), Aubrey Zerkle (St. Andrews, Scotland)), and others as this rare Earth crustal and oceanic interplay grows in significance.
This volume brings together contributions from the Royal Society Discussion Meeting on ‘Earth dynamics and the development of Plate Tectonics’ held in March 2018. Plate tectonics is not seen on other planets, so why does it occur on Earth, and when did it start? The nature of tectonics depends on initial conditions, mantle thermal states, and an ability to weaken the lithosphere to allow plate boundaries to form. Geodynamic models, rock deformation experiments, models for growth of the continental crust, and evidence from the rock record are consistent with the development of plate tectonics from a single-lid state. Major changes occurred in the geological record near the end of the Archaean, suggesting that plate tectonics had become the dominant gobal regime by the Proterozoic. Modern plate tectonics and the generation of stable continents were key events in the evolution of the biosphere on Earth, and similar tectonic processes could be crucial for the development of habitability of exoplanets. (Synopsis)
Armstrong, Stuart and Anders Sandberg. Eternity in Six Hours: Intergalactic Spreading of Intelligent Life and Sharpening the Fermi Paradox. Acta Astronautica. 89/1, 2013. The physicist Enrico Fermi famously asked in the 1950s that for a universe then thought to be rife with advanced civilizations, so “Where is everybody?” This question has been much debated since, a Wikipedia entry under its name provides a good survey. Here Oxford University, Future of Humanity Institute, philosophers contend that galactic travel and celestial reengineering are really not prohibitive, so once a world which did not destroy itself got unified and going, they should have formed evident reconstructions. But nothing like a “Dyson sphere” built by a civilization around its star has been seen. Even though Kepler satellite discoveries forecast some quintillions of earth-like bioplanets across galactic spacescape, the authors go on to allude that there may not be anyone else out there.
The Fermi paradox is the discrepancy between the strong likelihood of alien intelligent life emerging (under a wide variety of assumptions) and the absence of any visible evidence for such emergence. In this paper, we extend the Fermi paradox to not only life in this galaxy, but to other galaxies as well. We do this by demonstrating that travelling between galaxies – indeed even launching a colonisation project for the entire reachable universe – is a relatively simple task for a star-spanning civilisation, requiring modest amounts of energy and resources. We start by demonstrating that humanity itself could likely accomplish such a colonisation project in the foreseeable future, should we want to. Given certain technological assumptions, such as improved automation, the task of constructing Dyson spheres, designing replicating probes, and launching them at distant galaxies, become quite feasible. We extensively analyse the dynamics of such a project, including issues of deceleration and collision with particles in space. Using similar methods, there are millions of galaxies that could have reached us by now. This results in a considerable sharpening of the Fermi paradox. (Abstract)
Arnould, Jacques. Astrobiology, Sustainability and Ethical Perspectives. Sustainability. 1/4, 2009. In this online journal which has become a home for authoritative writings about saving the planet, a CNES French Space Agency philosopher contends that an expansive panorama that views earth and human in the context of a conducive, life friendly cosmos could be of much utility and incentive.
Astrobiology, a new field of research associating the prospects and constraints of prebiotic chemistry, mineralogy, geochemistry, astrophysics, theoretical physics, microbial ecology, etc., is assessed in terms of sustainability through the scientific and social functions it fulfils, and the limits it encounters or strives to overcome. In the same way as sustainable development, astrobiology must also take into account the temporal dimension specific to its field of investigation and examine its underlying conception of Nature. (Abstract)
Bach-Muller, Nanna and Uffe Jorgensen. Orbital Eccentricity: Multiplicity Correlation for Planetary Systems and Comparison to the Solar System. arXiv:2010.10371. As exoplanet findings grow in number and variety, Niels Bohr Institute, University of Copenhagen astroscientists can perceive another unusual aspect of our home orrery. With regard to most other systems with a few worlds, our 8 or 9 member planets as well as their relatively round orbit and even spacings is a quite rare confluence. As we post in late 2020 with our precious, precarious Earth beset by so many perils, this awesome significance grows in validity. See also Solid Tidal Friction in Multi-layer Planets by Emeline Bolmont, et al at 2010.04587.
The orbit eccentricities of the Solar System planets are unusually low compared to the average of known exoplanetary systems. A power law correlation has been found between the multiplicity of a planetary system and the orbital eccentricities of its components for systems above two worlds. In this study we investigate the correlation for an expanded data sample by way of planetary systems as units (unlike studies of individual planets). Our full survey contains 1171 exoplanets in 895 systems whence the correlation between eccentricity and multiplicity follows a clear power law. We find that Solar System orbits fit the general trend and suggest that the Solar System might not show uncommonly low eccentricities but rather more planets compared to a "standard" planetary system. Based on the power law correlation, we estimate that the probability of a system having 8 planets or more is of the order of 1%. (Abstract excerpt)
Balbi, Amedeo and Adam Frank.
The Oxygen Bottleneck for Technospheres.
After some 15 years of habitable exoworld studies across solar system and galactic zones, University of Rome and University of Rochester astrophysicists (search each) realize that the narrow O2 window between enough for fauna to breathe but not for flora to combust is a prime parameter with regard to possible intelligent civilizations. At this juncture, one more
On Earth, the development of technology required easy access to open air combustion, which is only possible when oxygen partial pressure, P(O2), is above 18\%. This suggests that only planets with significant atmospheric oxygen concentrations will be capable of developing advanced technospheres.
Balbi, Amedeo and Francesco Tombesi. The Habitability of the Milky Way during the Active Phase of its Central Supermassive Black Hole. Nature Scientific Reports. 7/16626, 2017. Vergata University of Rome astrophysicists add still another deleterious impediment due to excessive galactic radiations from the main galactic black hole which prohibit the long multi-million year span necessary for organisms to form, evolve and complexify.
During the peak of their accretion phase, supermassive black holes in galactic cores are known to emit very high levels of ionizing radiation, becoming visible over intergalactic distances as quasars or active galactic nuclei (AGN). Here, we quantify the extent to which the supermassive black hole at the center of the Milky Way may have affected the habitability of Earth-like planets. We focus on the amount of atmospheric loss and biological damage suffered by planets exposed to X-ray and extreme ultraviolet radiation. We find that terrestrial planets could lose a total atmospheric mass comparable to that of present day Earth even at large distances from the galactic center. (Abstract excerpt)
Ballmer, Maxim and Lena Noack. The Diversity of Exoplanets: From Interior Dynamics to Surface Expressions. arXiv:2108.08385. The paper also appears in a special issue Geoscience Beyond the Solar System issue of Elements magazine (17/4, 2021). University College London and Free University of Berlin astroscientists extend exoworld studies so as to factor in effects of variable internal compositions upon relative habitability. Indeed it is found that over eons and eras their core to crust fluctuations could play a major role. See also Starting Life and Searching for Life on Rocky Planets by Paul Rimmer, et al (2108.04.08388) in the same edition.
The coupled interior-atmosphere system of terrestrial exoplanets remains poorly understood. Exoplanets show a wide variety of sizes, densities, surface temperatures, and interior structures, which all effect this coupled system. Many exoplanets could have a "stagnant lid" at the surface, with a rigid stationary crust, sluggish mantle convection, and minor volcanism. However, if exoplanets have Earth-like plate tectonics and tectono-magmatic activity, then these features may be critical for planetary habitability and have implications for the development (and evolution) of life in the galaxy. (Abstract)
Testing the Multiverse: Bayes, Fine-Tuning and Typicality.
Reviewed more in Anthropic Principle, the University of Sydney astronomer (search) posts his presentation at a 2014 London Philosophy of Cosmology conference. As a coauthor with Geraint Lewis of A Fortunate Universe (2016), this entry discusses anthropic themes along with Bayesian “theory testing” methods for better iterations of “relative certainties or credences.” For this Greatest Earth section, it is wondrous that inquisitive, globally cognizant peoples can imagine whole cosmoses at all. With 400th anniversary events underway for Galileo, what can these expansive vistas from our moon to a multiverse ever portend? As latest currents seem to presage, human beings ought to have a significant purpose in the actual scheme of things.
Barnes, Rory. Tidal Locking of Habitable Exoplanets. Celestial Mechanics and Dynamical Astronomy. 129/4, 2017. A University of Washington astronomer quantifies one more crucial condition as to whether a candidate orbital world could harbor living, evolving systems, or be prohibitively hostile to it. Since this Earth has been benign long enough to reach our global observation, its tidal regime, in accord with the moon and sun, must have been fortuitous. See also Niche Amplitude, Tidal Locking and Fermi’s Paradox and Evolutionary Exobiology II by David Stevenson in the International Journal of Astrobiology (Each online July 2018).
Potentially habitable planets can orbit close enough to their host star that the differential gravity across their diameters can fix the rotation rate at a specific frequency, a process called tidal locking. Tidally locked planets on circular orbits will rotate synchronously, but those on eccentric orbits will either librate or rotate super-synchronously. Lower mass stellar hosts will induce stronger tidal effects on potentially habitable planets, and tidal locking is possible for most planets in the habitable zones of GKM dwarf stars. These results suggest that the process of tidal locking is a major factor in the evolution of most of the potentially habitable exoplanets to be discovered in the near future. (Abstract excerpt)
Batygin, Konstantin and Greg Laughlin. Jupiter’s Decisive Role in the Inner Solar System’s Early Evolution. Proceedings of the National Academy of Sciences. 112/4214, 2015. As the rush of Kepler satellite findings become assimilated, radical new understandings of near and far stellar-planetary topological and dynamical arrays are being realized. Here Cal Tech and UC Santa Cruz astronomers report another way that our home system is unusual because this gas giant served to sweep away an original phase of close in worlds that often wreak instabilities. A commentary in the same issue by Smadar Naoz notes that our “unique” arrangement is a “second generation” sequence. Along with nine planets in the same plane with circular orbits for over a billion years, it is dawning that we Earthlings abide in a rare, especially conducive, habitable zone.
The Solar System is an unusual member of the galactic planetary census in that it lacks planets that reside in close proximity to the Sun. In this work, we propose that the primordial nebula-driven process responsible for retention of Jupiter and Saturn at large orbital radii and sculpting Mars’ low mass is also responsible for clearing out the Solar System’s innermost region. Cumulatively, our results place the Solar System and the mechanisms that shaped its unique orbital architecture into a broader, extrasolar context. (Significance)