VII. Pedia Sapiens: A Genesis Future on Earth and in the Heavens
C. An Earthropic Principle: Novel Evidence About a Special Planet
Olson, Stephanie, et al. Oceanographic Constraints on Exoplanet Life. arXiv:1909.02928. With our favorable tectonic balance of land and sea as a reference, University of Chicago geophysicists including Dorian Abbot consider variable exoworld oceanic conditions with regard to the presence of living systems. This liquid, amniotic surface hydrosphere is also seen as a major factor in their relative biological detectability. See also Scaling Relations for Terrestrial Exoplanet Atmospheres from Baroclinic Criticality by this extended group at 1908.02661 for more vital properties.
Liquid water oceans are crucial to our search for life on exoplanets because water is essential for life as we know it. However, oceans are dynamic habitats and some may be better hosts for life than others. In Earth's oceanic circulation conveys nutrients such as phospourous which affects the distribution and productivity of life. Of importance is upwelling due to wind-driven divergence in surface layers, which returns nutrients that tend to accumulate at depth. We address these aspects by using ROCKE-3D, a fully coupled ocean-atmosphere GCM, to investigate ocean dynamics on a diversity of habitable planets. Efficient nutrient recycling favors greater biological activity for better biosignature detection. Our results demonstrate the importance of oceanographic phenomena for exoplanet life detection and the emerging field of exo-oceanography. (Abstract excerpt)
Ono, Yoko. My Friends. New York Times. December 28, 2003. A full page placement with these few lines of Yoko Ono’s New Year sentiments and advice for a distraught and percipitous world.
Paradise, Adiv, et al. Climate Diversity in the Habitable Zone due to Varying pN2 Levels. arXiv:1910.02355. As if we did not already have enough finely tuned conditions which serve to make this home habitable Earth so very special, here University of Toronto astrophysicists and a biologist point out that an optimum band and pressure of atmospheric nitrogen is another vital parameter. For our bioplanet, it nominally is 79% and 21% oxygen within a tight zone of a few percent either way. In addition this range which has remained relatively stable for millions of years.
A large number of studies have responded to the growing body of confirmed terrestrial habitable zone exoplanets by presenting models of various possible climates. However, the impact of the partial pressure of gases such as N2 has been poorly-explored, despite the abundance of N2 in Earth's atmosphere. We use PlaSim, a fast 3D climate model, to simulate hundreds of climates with varying N2 pressures, insolations, and surfaces to identify the impact of the gas partial pressure on the climate. We find that the climate's response is nonlinear and highly sensitive to this factor. We identify CO2 and H2O absorption lines, warming or cooling by the water vapor greenhouse positive feedback, heat transport, and more as competing mechanisms that determine the equilibrium climate. (Abstract excerpts)
Pilat-Lohinger, Elke. The Role of Dynamics on the Habitability of an Earth-like Planet. International Journal of Astrobiology. 14/2, 2015. In an Exoplanet issue, a University of Vienna astrophysicist reaches a notable conclusion about our own solar system. It seems especially conducive because the orbital planets all lie in the same plane, and have basically circular orbits. Such a relative stability over a long time period is most favorable for a suitable biosphere upon which life can evolve and emerge to a noosphere able to observe itself and a planetary neighborhood.
Provenzale, Murante, et al. Climate Bistability of Earth-like Planets. arXiv:1912.05392. Eleven astroscientists from Torino to Trieste report that our own world seems to have passed through both colder, icy states and warmer, watery times. By these findings, this prior occasion appears as dual climatic options, depending on relative levels of energetic forcings. And as noted, such dynamic shiftings may play a serious role as evolutionary organisms may proceed on their course.
About 500 million years ago, our planet seems to have experienced snowball conditions, with continental and sea ices covering a large fraction of its surface. This situation points to a potential bistability of Earth's climate, that can have at least two equilibrium states for the same external solar radiation forcing. Here we explore the probability of bistable climates in earth-like exoplanets, and the properties of planetary climates obtained by varying the semi-major orbital axis, eccentricity, obliquity, and atmospheric pressure. To this goal, we use the Earth-like surface temperature model (ESTM) to provide a climate estimator for parameter sensitivity and long climatic simulations. An intriguing result of the present work is that the planetary conditions that support climate bistability are remarkably similar to those required for the sustenance of complex, multicellular life on the planetary surface. (Abstract excerpt)
Quarles, Billy, et al. Obliquity Evolution of Circumstellar Planets in Sun-like Stellar Binaries. arXiv:1911.08431. We add this report by Georgia Tech and NASA astronomic researchers including Jack Lissauer because it broaches another vicarious variable which could influence for better or worse life’s chances to evolve and reach global abilities to retrospectively perceive realize this reality.
Changes in planetary obliquity, or axial tilt, influence the climates on Earth-like planets. In the solar system, the Earth's obliquity is stabilized due to our moon which causes small amplitude variations beneficial for advanced life. Most Sun-like stars have at least one stellar companion and the habitability of their exoplanets is shaped by these pairings. We show that a stellar companion dramatically effects whether an Earth-like obliquity stability is possible. We present a new formalism for the planetary spin precession that accounts for orbital misalignments between the planet and binary. Thus, Earth-like planets likely experience much larger obliquity variations, with more extreme climates, unless they are in specific favorable states. (Abstract excerpt)
Ramirez, Rodrigo, et al. New Numerical Determination of Habitablility in the Galaxy. International Journal of Astrobiology. Online March, 2017. Universidad Nacional Autonoma de Mexico and Instituto de Estudios Avanzados de Baja, California astrophysicists finesse quantifications of the relative galactic and cosmic occurrence of planetary life. While rudimentary organisms may likely proliferate, a global evolution of technological civilizations may be less common and hardly detectable.
Raymond, Sean. Sculpting Our Planetary System. American Scientist. September-October, 2018. In an issue on the many ways that Big Data/AI methods are bringing new capabilities to astronomical studies, a Laboratoire d’ Axtrophysique de Bordeaux researcher describes a novel, quite chaotic picture of how orbital worlds and solar systems form and evolve. Our familiar, orderly array, which was long taken as a norm, now seems a rare benign state as we learn about a usual crush of super-Earths, gas giants and rocky worlds in wildly shifting transits. See also by Formation of Terrestrial Planets by Raymond and Andre Izidoro at arXiv:1803.08830 and The Excitation of a Primordial Cold Asteroid Belt as an Outcome of the Planetary Instability by their group (1808.00609). The issue contains many entries from computations and astrochemistry to gravity waves and exoplanets.
The discovery of thousands of planets orbiting other stars has given us three surprising insights about our Solar System. First, we are weird: Our Solar System is a 1-in-2,000 rarity. Second, planet formation is a dynamic process, characterized by large-scale orbital drift as well as violent collisions and the ejection of young planets into interstellar space. Lastly, the second point may explain the first one—that is, how our Solar System formed is likely the root cause of our weirdness. (280)
Raymond, Sean, et al. Solar System Formation in the Context of Extra-Solar Planets. arXiv:1812.01033. Senior astrophysicists SR, University of Bordeaux, Andre Izidoro, Sao Paulo State University and Alessandro Morbidelli, University of Nice (search each) post a strongest analysis to date that our home Earth-Sun spatial and temporal array seems to be a rarest long term orderly, benign, conducive milieu for life to evolve and develop to a personsphere intelligence able to reach this auspicious conclusion. At the cusp of 2020, here is an incredible finding in our midst with implications for the fate and future not only of a geonate EarthKinder, but on to a self-chosen Ecosmos.
Exoplanet surveys have confirmed one of humanity's worst fears: we are weird. If our Solar System were observed with present-day Earth technology -- to put our system and exoplanets on the same footing -- Jupiter is the only planet that would be detectable. The statistics of exo-Jupiters indicate that the Solar System is unusual at the ~1% level among Sun-like stars (or ~0.1% among all stars). But why are we different? We argue that most Earth-sized habitable zone exoplanets are likely to form much faster than Earth, with most of their growth complete within the disk lifetime. Their water contents should span a wide range, from dry rock-iron planets to water-rich worlds with tens of percent water. Jupiter-like planets on exterior orbits may play a central role in the formation of planets with small but non-zero, Earth-like water contents.
Rees, Martin. Is There Life Beyond Earth? New Scientist. July 12, 2003. More considerations by the Cambridge University astronomer about the future options and august purpose for an integral earthkind in the universe.
More time lies ahead than has elapsed in the entire course of biological evolution. In those aeons, Earth could be the “seed” from which post-human life spreads through the galaxy. The fate of humanity could then have an importance that is truly cosmic: what happens here might conceivably make the difference between a near eternity filled with ever more complex and subtle forms of life and one filled with nothing but base matter. (27)
Rees, Martin. Living in a Multiverse. Ellis, George F. R., ed. The Far-Future Universe: Eschatology from a Cosmic Perspective. Philadelphia: Templeton Foundation Press, 2002. In his many universe scenario, only those finely tuned for life can contain intelligent planetary beings who are able to learn, contemplate and creatively carry forth this genesis. (Noted again in The Greening of the Galaxy)
Our Earth may have cosmic importance, as the one place form which life could spread through the universe. This realization raises the stakes from the earth to the entire cosmos. This new century, on this planet may be a defining moment for the cosmos. In the entire domain that cosmologists explore – ten billion years of time, ten billion light-years of space – the most crucial space-time location of all could be here and now. (84)
Sagan, Dorion. Biospheres. New York: McGraw-Hill, 1990. Prescient speculations from a Vladimir Vernadsky and Gaian perspective on how earth seems primed for a biological metamorphosis which spawns self-contained, autopoietic colonies. A key tenet is a fractal creation which recovers the ancient microcosm/macrocosm correspondence in a evolutionary universe.
Looking forward, it is possible to imagine a scenario in which the cosmos becomes animated in a way our intellectual forerunners and midnight star-gazers may never have imagined: if life continues to unfold “fractally” in the direction set down here - with individuality reestablishing itself at ever greater levels - biospheres will till the virgin soil of space itself… (184)