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Recent Additions: New and Updated Entries in the Past 60 Days
Displaying entries 61 through 64 of 64 found.


Pedia Sapiens: A Genesis Future on Earth and in the Heavens

Future > Self-Selection

Kopparapu,, Ravi, et al. Characterizing Exoplanet Habitability. arXiv:1911.04441. A chapter to appear in Planetary Astrobiology (University of Arizona Press, February 2020) by RK, Goddard Space Center, Eric Wolf, University of Colorado, and Victoria Meadows, University of Washington. As stellar, galactic, and universal frontiers open up to satellite, atmospheric, spectroscopy, geologic, computational prowess and other survey, our home ovoworld embarks upon a cosmic neighbor census. But as explorations go forth they are finding stochastic, vicarious environs which winnow down habitation via a train of conducive conditions that must be met. A Factors Affecting Habitability graphic depicts some 50 issues such as sun type, spectral energy, solar orbits, metallicity, UV rays, watery basins, a mediating moon. As this section records, it should soon dawn upon us that a population of one Earthropic optimum may only 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)

Future > Self-Selection

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)

Future > Self-Selection

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)

Future > Self-Selection

Secco, Luigi, et al. Habitability of Local, Galactic and Cosmological Scales. arXiv:1912:01569. University of Padova astroscientists consider these near and far domains by way of the latest exoplanet and exosolar findings and again reach an auspicious conclusion. An “Earth peculiarity” appears due to features such as an optimum orbit around the sun, benign solar system, magnetic field strength, good nitrogen to oxygen ratio, ocean to land plate tectonics, an ideally placed large moon, obliquity tilt, and more. Akin to Planetary Astrobiology by Victoria Meadows, et al (2019, 2020 herein), as the second quotes alludes out of a concatenation of some 1020 candidate worlds, our emergent person/sapiensphere progeny could very well be its first, best, or last universal opportunity to observe, read, affirm self-select and begin a new creation.

The aim of this paper is to underline conditions necessary for the emergence and development of life. They are placed at a local planetary scale, a Galactic scale and within cosmic evolution. We will consider the circumstellar habitable zone (CHZ), a Galactic Habitable Zone (GHZ), and also a set of strong cosmological constraints to allow Anthropic life. Some requirements are specific to a single scale and their physical phenomena, while others are due to cumulative effects across scales. A surmise is that all the habitability conditions here so detailed must at least be met. Thus, some sixty years later a human-like presence may appear as "a monstrous sequence of accidents" as (Fred) Hoyle (1959) thought, or as a providential collaboration which can imply how finely tuned is the architecture within which precious Life is embedded. (Abstract edits)

Starting from the local scale, life leads to connect us with the largest scale, that of Universe. From this analysis a possible scenario arises in which links among the different scales are advanced. Even if possibly partial, a large set of minimum conditions has been identified which must be met for allowing life. The consequence of these conditions is that if we look at life from the probability point of view and then regard it as a complex phenomenon composed, by compatible and independent events, the probability to get it tends drastically to zero. But here we are! (24)

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