VIII. Pedia Sapiens: A New Genesis Future
C. An Earthropic Principle: Novel Evidence for a Special Planet
Horner, Jonathan, et al. The Influence of Jupiter, Mars and Venus on Earth’s Orbital Evolution. arXiv:1708.03448. Australian and British astroscientists including David Waltham consider still another closely finessed attribute of this solar system which is necessary for an extended benign period of Earth life evolution.
n the coming years, it is likely that the first potentially Earth-like planets will be discovered orbiting other stars. Once found, the characterisation of those planets will play a vital role in determining which will be chosen as the first targets for the search for life beyond the Solar System. One of the plethora of factors to be considered in that process is the climatic variability of the exo-Earths in question. In the Solar System, the Earth's long-term climate is driven by several factors, including the modifying influence of life on our atmosphere, and the temporal evolution of solar luminosity. The gravitational influence of the other planets in the Solar System adds an extra complication, driving the Milankovitch cycles (2nd quote) that are thought to have caused the on-going series of glacial and interglacial periods that have dominated Earth's climate for the past few million years. Our results illustrate how small changes to the architecture of a given planetary system can result in marked changes in the potential habitability of the planets therein, and are an important first step in developing a means by which the nature of climate variability on planets beyond our Solar System can be characterised. (Abstract)
Jones, Barrie. The Search for Life Continued: Planets Around Other Stars. Berlin: Springer, 2008. The Open University astronomer provides a thorough, illustrated guide for the outward quest for animate worlds and entities across the galaxy and cosmos. This endeavor has taken on a new dimension with the ability to search for and detect similar earths orbiting distant suns. Their apparent proliferation provides another good reason that we are not alone and could inspire us earthlings to join in a sustainable initiative and destiny.
Kodama, Takanori, et al. Inner Edge of Habitable Zones for Earth-sized Planets with Various Surface Water Distributions. Journal Geophysical Research Planets.. Online August, 2019. University of Bordeaux, University of Tokyo, Japan Agency for Marine-Earth Science, and Tokyo Institute of Technology researchers find that the occasion global oceanic presence, which is vital for life to form and evolve, is actually a rare, chancy situation which often shifts to an all wet or dry regime due to many celestial forces.
Kokaia, Giorgi, et al. Resilient Habitability of Nearby Exoplanet Systems. arXiv:1910.07573. Lund University, Sweden astrophysicists study some 34 candidate solar systems that appear to have been influenced at some point by a giant planet. While a relative habitable phase might return, it is concluded that this result would be a rare event. We cite the paper as another example of how planetary arrays seem to be more often so vulnerable to chaotic disruption and instabilities over their duration.
Kopparapu,, Ravi, et al. Characterizing Exoplanet Habitability. Meadows, Victoria, et al, eds. Planetary Astrobiology. Tempe: University of Arizona Press, 2020. As stellar, galactic, and universal frontiers open to satellite, atmospheric, spectroscopy, geologic, computational and other surveys, RK, Goddard Space Center, Eric Wolf, University of Colorado, and Victoria Meadows, University of Washington discuss how to proceed with a cosmic neighbor census. But as explorations go forth they are finding vicarious contingencies which winnow habitations by way of a long series of conducive conditions that must be met. A large Factors Affecting Habitability graphic depicts some 50 issues such as sun type, spectral energy, solar orbits, metallicity, UV rays, watery basins, a mediating moon and so on. As this section records, it ought to soon dawn upon us that a population of only one fittest Earthropic optimum may exist. See also How to Characterize Habitable Worlds and Signs of Life by Lisa Kaltenegger in the Annual Review of Astronomy and Astrophysics (55/433, 2017).
Habitability is a measure of an environment's potential to support life, which means liquid water on its surface. This condition depends on a complex set of interactions between planetary, stellar, planetary system and even galactic features and processes. We describe the latest way to test which exoplanets are likely to be terrestrial, and how to define the habitable zone under different assumptions. We are now entering an exciting era of exoplanet atmospheric studies, with more powerful observing capabilities planned for the near and far future. Understanding the processes that affect the habitability of a planet will guide us in discovering habitable, and potentially inhabited, planets. (Abstract excerpt)
Kouvenhoven, M. B. N, et al. Planetary Systems in Star Clusters. arXiv:1609.00898. After two decades of scientific realizations of a radically different cosmos that fills itself with planetary objects of all manner of types, sizes and stellar locales, a team of astrophysicists with joint Chinese and Dutch postings add another observation of how our own sun system is uniquely special. Most stars, as also galaxies, actually tend to collect and bunch together, so that planets in these jumbled environs are not in circular orbits but “scatter and disperse” widely.
Thousands of confirmed and candidate exoplanets have been identified in recent years. Consequently, theoretical research on the formation and dynamical evolution of planetary systems has seen a boost, and the processes of planet-planet scattering, secular evolution, and interaction between planets and gas/debris disks have been well-studied. Almost all of this work has focused on the formation and evolution of isolated planetary systems, and neglect the effect of external influences, such as the gravitational interaction with neighbouring stars. Most stars, however, form in clustered environments that either quickly disperse, or evolve into open clusters. Under these conditions, young planetary systems experience frequent close encounters with other stars, at least during the first 1-10 Myr, which affects planets orbiting at any period range, as well as their debris structures. (Abstract)
Lammer, Helmet, et al. The Role of Nitrogen as a GeoBiosignature for the Detection and Characterization of Earth-like Habitats. arXiv:1904.11716. A seven member group mainly from the Austrian Academy of Sciences Space Research Institute cites that the appropriate presence of this globally atmospheric and chemical element ought to be seen as another important factor for life’s emergent evolution.
Since the Archean, nitrogen has been a major atmospheric constituent in Earth's atmosphere. It is an essential element in the building blocks of life, therefore the geobiological nitrogen cycle is a fundamental factor in the long term evolution of both Earth and Earth-like exoplanets. We discuss the development of the Earth's N2 atmosphere since the planet's formation and its relation with the geobiological cycle. Then we suggest atmospheric evolution scenarios and their possible interaction with life forms for a stagnant-lid anoxic world, a tectonically active anoxic world, and an oxidized tectonically active world. Since life forms are the most efficient means for recycling deposited nitrogen back into the atmosphere nowadays, they sustain its surface partial pressure at high levels. (Abstract excerpt)
Lineweaver, Charles and Molly Townes O’Brien. The Cosmic Context of the Millennium Development Goals: Maximum Entropy and Sustainability. Thomas Faunce, ed. Nanotechnology Toward the Sustainocene. Singapore: Pan Stanford Publishing, 2015. An Australian National University astronomer and law professor expansively situate our crucial imperative to achieve a better populace and planet within a widest temporal and spatial evolutionary locus. In this whole scenario, a global transition to organic viability would contribute to the arrow and advance of informed, personified order over disorderly dissipations.
Life forms are a subset of the organized structures in the universe known as far-from equilibrium dissipative systems (FarFEDS). FarFEDS are dissipative structures that, while maintaining their structure, convert low-entropy energy to high-entropy energy. They include galaxies, stars, convection cells, typhoons, fires, humans, and bacteria. All FarFEDS (and thus all life forms) extract free energy from the environment and turn it into waste heat faster than random processes such as diffusion would be able to do. (41-42)
Lingam, Manasvi. Implications of Abiotic Oxygen Buildup for Earth-like Complex Life. arXiv:2002.03248. A Florida Institute of Technology astrophysicist (search) surveys the importance for a bioworld to achieve a favorable atmospheric O2 level in the low 20% range for life to be able to develop and evolve. This small window between starved and burnt up need be reached in a timely way (Lineweaver) and persist over relatively long periods. This atmospheric quality would then be a vital biosignature. See also Ward, Lewis, et al. Follow the Oxygen: Comparative Histories of Planetary Oxygenation and Opportunities for Aerobic Life by Lewis Ward, et al in Astrobiology (19/6, 2019). In regard, still another vital, finely tuned check point to successfully pass through is highlighted.
One of the chief paradoxes of molecular oxygen (O2) is that it is an essential requirement for multicellular eukaryotes on Earth while simultaneously posing a threat to their survival via the formation of reactive oxygen species. In this paper, the constraints imposed by O2 on Earth-like complex life are applied to whether worlds with abiotic O2 inventories can harbor such organisms. By consideration of the O2 sources and sinks of Earth-like planets, it is proposed that worlds with X-ray and extreme ultraviolet fluxes might not host complex lifeforms because the photolysis of water molecules may cause high O2 buildup. (Abstract excerpt)
Lingam, Manasvi and Abraham Loeb. Dependence of Biological Activity on the Surface Water Fraction of Planets. arXiv:1809.09118. The Harvard University, Institute for Theory and Computation postdoc and director team (search) continue their studies of extraterrestrial life by noting a critically vital feature of this habitable Earth, namely a 30% land and 70% ocean ratio maintained over some three billion years. As such multiphase exoplanet research proceeds apace, it is becoming evident that this dual division is a rarest state. The common spherical default is wholly dry, watery or gaseous. Plate tectonic movements are then seen to add a significant favorable condition (still going on in the Pacific rim of fire). A previous entry (L & L, 1804.02271) considered the effect of stellar physics on planetary life. As this section seeks to report, our home sapient Earth seems to be an increasingly special bioplanet amongst myriad vicarious candidates. This is an awesome, unexpected finding in need of much public report and notice, at a same time when nuclear nations are in headlong regression.
One of the unique features associated with the Earth is that the fraction of its surface covered by land is comparable to that spanned by its oceans and other water bodies. Here, we investigate how extraterrestrial biospheres depend on the ratio of the surficial land and water fractions. We find that worlds that are overwhelmingly dominated by landmasses or oceans are likely to have sparse biospheres. Our analysis suggests that major evolutionary events such as the buildup of O2 in the atmosphere and the emergence of technological intelligence might be relatively feasible only on a small subset of worlds with surface water fractions ranging approximately between 30% and 90%. We also discuss how our predictions can be evaluated by future observations, and the implications for the prevalence of microbial and technological species in the Universe. (Abstract)
Lingam, Manasvi and Abraham Loeb. Implications of Tides for Life on Exoplanets. arXiv:1707.04594. Harvard-Smithsonian Center for Astrophysics theorists consider this geospheric surface condition which could have a major influence on long-term habitability. Our own Earth-moon system is an optimum situation of moderate tidal flows and basins, whereof cellular life can begin its evolutionary course. However, on the many other exoworlds just being found, this stable state maybe a rare occurrence. A corollary or default phase has become known “tidal locking” whence an orbiting object enters a tandem rotation with a host star or moon, see Tidal Locking of Habitable Exoplanets by Rory Barnes herein.
As evident from the nearby examples of Proxima Centauri and TRAPPIST-1, Earth-sized planets in the habitable zone of low-mass stars are common. Here, we focus on such planetary systems and argue that their (oceanic) tides could be more prominent due to stronger tidal forces. We identify the conditions under which tides may exert a significant positive influence on biotic processes including abiogenesis, biological rhythms, nutrient upwelling and stimulating photosynthesis. We conclude our analysis with the identification of large-scale algal blooms as potential temporal biosignatures in reflectance light curves that can arise indirectly as a consequence of strong tidal forces. (Abstract)
Lingam, Manasvi and Abraham Loeb. Physical Constraints for the Evolution of Life on Exoplanets. arXiv:1810:02007. Some two weeks after a posting (1809.09118, see also 1807.08879, 1804.02271) about how plate tectonics can effect habitability, this Harvard team, funded in part by the Breakthrough Foundation, here view additional vicarious cosmic, solar, and geologic influences such as stellar coronal winds and flares, planetary magnetospheres, oceanic and atmospheric evaporations, electromagnetic radiation, relative oxygen buildup, origins of life, photosynthesis, and more in mathematic detail. These studies are then supported with some 300 references. Once again, this home Earth whereupon a sapient species is altogether able to explore, quantify and learn, seems to be an increasingly unique candidate personsphere.
Some two weeks after a posting (1809.09118, see also 1807.08879, 1804.02271) about how plate tectonics can effect habitability, this Harvard team, funded in part by the Breakthrough Foundation, here view additional vicarious cosmic, solar, and geologic influences such as stellar coronal winds and flares, planetary magnetospheres, oceanic and atmospheric evaporations, electromagnetic radiation, relative oxygen buildup, origins of life, photosynthesis, and more in mathematic detail. These studies are then supported with some 300 references. Once again, this home Earth whereupon a sapient species is altogether able to explore, quantify and learn, seems to be an increasingly unique candidate personsphere.