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

H. Stellar Planetary Systems: A Stochastic Profusion of Galaxies, Solar Orrerys, and Habitable Zones

Tremaine, Scott. The Statistical Mechanics of Planet Orbits. arXiv:1504.01160. It is noteworthy in this post-Kepler era of myriad solar systems that scientists such as this Institute for Advanced Study, Princeton University, astrophysicist and leading expositor of galactic dynamics, can consider a common physical theory by which planetary bodies arrange themselves. On this e-print site and across the astro- journals, articles like Spacing of Kepler Planets: Sculpting by Dynamical Instability (1502.05449) and Consolidating and Crushing Exoplanet (1502.06558) now treat solar system formations as a valid subject amenable to theoretical explanations.

The final "giant-impact" phase of terrestrial planet formation is believed to begin with a large number of planetary "embryos" on nearly circular, coplanar orbits. Mutual gravitational interactions gradually excite their eccentricities until their orbits cross and they collide and merge; through this process the number of surviving bodies declines until the system contains a small number of planets on well-separated, stable orbits. In this paper we explore a simple statistical model for the orbit distribution of planets formed by this process, based on the sheared-sheet approximation and the ansatz that the planets explore uniformly all of the stable region of phase space. The model provides analytic predictions for the distribution of eccentricities and semimajor axis differences, correlations between orbital elements of nearby planets, and the complete N-planet distribution function, in terms of a single parameter that is determined by the planetary masses. The predicted properties are generally consistent with both N-body simulations and the Kepler catalog of extrasolar planets. A similar model may apply to the orbits of giant planets if these orbits are determined mainly by dynamical evolution after the planets have formed and the gas disk has disappeared. (Abstract)

Turbet, Martin, et al. CO2 Condensation is a Serious Limit to the Deglaciation of Earth-like Planets. arXiv:1703.04624. Sorbonne, Bordeaux, and Nantes University astroresearchers, including Francois Forget, identify another critically poised exoplanetary feature vital for life and evolution. Intricate, geochemical dynamics produce and interact with carbon dioxide levels in exoatmospheres, which then affects the degree of colder or warmer conditions. Another window of viability thus seems to be balanced between a frigid frozen or hot gaseous world. Search here for Haqq-Misra, Jacob, et al for another angle on this.

It is widely believed that the carbonate-silicate cycle is the main agent to trigger deglaciations by CO2 greenhouse warming on Earth and on Earth-like planets when they get in frozen state. Here we use a 3D Global Climate Model to simulate the ability of frozen planets to escape from glaciation by accumulating enough gaseous CO2. We find that Earth-like planets orbiting a Sun-like star may never be able to escape from glaciation if their orbital distance is greater than ∼ 1.27 AU (Flux < 847 W m−2), because CO2 would condense at the poles forming permanent CO2 ice caps. This limits the amount of CO2 in the atmosphere and thus its greenhouse effect. Our results may have implications for the search for life-suitable extrasolar planets orbiting in the Habitable Zone of Sun-like stars.
(Abstract excerpts)

Valencia, Diana. Composition and Internal Dynamics of Super-Earths. Karato, Shun-ichiro, ed.. Physics and Chemistry of the Deep Earth. Chichester, UK: Wiley-Blackwell, 2013. Into this 21st century, it is worth notice that the composite collaboration of a sentient, linguistic, technological species now of global cast and import, can proceed to so explore, name, quantify, and describe these depths of these myriad orbiting worlds. We cite this chapter by a Sagan NASA postdoctoral fellow (mellow) at MIT, to illustrate how our novel collective abilities can span the planet-filled galactic reaches.

Though the deep interior of the Earth (and other terrestrial planets) is inaccessible to humans, we are able to combine observational, experimental and computational (theoretical) studies to begin to understand the role of the deep Earth in the dynamics and evolution of the planet. This book brings together a series of reviews of key areas in this important and vibrant field of studies. A range of material properties, including phase transformations and rheological properties, influences the way in which material is circulated within the planet. This circulation re-distributes key materials such as volatiles that affect the pattern of materials circulation. The understanding of deep Earth structure and dynamics is a key to the understanding of evolution and dynamics of terrestrial planets, including planets orbiting other stars. This book contains chapters on deep Earth materials, compositional models, and geophysical studies of material circulation which together provide an invaluable synthesis of deep Earth research. (Publisher)

My research comprises the characterisation of the low-mass planets: super-Earths and mini-Neptunes. The former are planets that are mostly solid, either rocky or icy in composition, while the latter posses also a volatile envelope. My goal is to determine if planets with masses between 1-15 Earth-masses are scaled up versions of Earth, or scaled-down versions of Neptune in terms of their composition, evolution and physical properties. To date, out of the ~600 discovered exoplanets, and 1000+ planet candidates reported by space mission Kepler, there are a handful of low-mass planets with measured masses and radii. This number will continue to increase as new data from Kepler arrives, and new discoveries are reported from other missions such as ground-based MEarth, or space mission CoRoT, as well as follow-up work to radial velocity planets. (DV website)

Valencia, Diana, et al. Radius and Structure of the First Super-Earth Planet. Astrophysical Journal. 656/545, 2007. Improved viewing and survey methods allow a new domain of terrestrial, rocky planets to be detected. Dubbed “super-earths” for their affinity to our home stone, they are somewhat larger in mass but by orders of magnitude as previous gas giants.

Vannah, Sara, et al.. An Information Theory Approach to Identifying Signs of Life on Transiting Planets.. Monthly Notices of the Royal Astronomical Society: Letters. October, 2023. SV and Marcelo Gleiser, Dartmouth College and Lisa Kaltenegger, Cornell University astrobiologists propose a novel way to detect advanced bioworld habitation by an evidential notice of a semblance of various communicative content.

Here we apply information theory to a range of simulated exoplanet transmission spectra as a diagnostic tool to search for potential signatures of life on Earth-analog planets. We test the algorithms on three epochs of evolution for Earth-like planets orbiting a range of host stars. The James Webb Space Telescope and upcoming ground- and space-based mironinssions promise to achieve sufficient high-resolution data that information theory can be applied to assess habitability. (Abstract)

This approach provides a framework and a tool for observers to assess exoplanet spectra. Just as we analysed simulated transmission spectra of Earth-like planets at different ages and around host stars in this paper, observed exoplanet spectra could be compared to modern Earth. Additionally, this approach is not limited to Earth-like planets or to identifying signs of life. This framework can similarly be used to compare an exoplanet spectrum to any Solar System object, or any specifically selected exoplanet to look for similarities.(6)

Vazquez, Manuel, et al, eds. The Earth as a Distant Planet: A Rosetta Stone for the Search of Earth-like Worlds. New York: Springer, 2010. As this 21st century project goes forward, little noticed by the general public, a comprehensive survey from the Instituto de Astrofisica de Canarias, Tenerife, explores how evidences from our own home, the one iconic world we can know, might guide this grand cosmic quest.

Vedantham, H. K., et al. Coherent Radio Emission from a Quiescent Red Dwarf Indicative of Star-Planet Interaction. arXiv:2002.08727. We cite this entry by fourteen astronomers from the Netherlands, France, the USA, Scotland, Germany, and Ireland to record how a sunny star and its orbital worlds altogether compose a dynamic system as if, to take license, as a solar incubator.

Veras, Dimitri. The Fates of Solar System Analogues with One Additional Distant Planet. arXiv:1608.07580. As the list of uniquely favorable features of our home planet and solar system for regnant life and humanity continues to grow, a University of Warwick astrophysicist theorizes that this eight world orrery – Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, sans dwarf Pluto – would become unstable if a further ninth planet was present. See also by DV the papers Relating Binary-Star Planetary Systems to Central Configurations (1607.08606), and Post-Main Sequence Planetary System Evolution (1601.05419.

The potential existence of a distant planet ("Planet Nine") in the Solar system has prompted a re-think about the evolution of planetary systems. As the Sun transitions from a main sequence star into a white dwarf, Jupiter, Saturn, Uranus and Neptune are currently assumed to survive in expanded but otherwise unchanged orbits. However, a sufficiently-distant and sufficiently-massive extra planet would alter this quiescent end scenario through the combined effects of Solar giant branch mass loss and Galactic tides. Here, I estimate bounds for the mass and orbit of a distant extra planet that would incite future instability in systems with a Sun-like star and giant planets with masses and orbits equivalent to those of Jupiter, Saturn, Uranus and Neptune. I find that this boundary is diffuse and strongly dependent on each of the distant planet's orbital parameters. Nevertheless, I claim that instability occurs more often than not when the planet is as massive as Jupiter and harbours a semimajor axis exceeding about 300 au, or has a mass of a super-Earth and a semimajor axis exceeding about 3000 au. This instability scenario might represent a common occurrence, as potentially evidenced by the ubiquity of metal pollution in white dwarf atmospheres throughout the Galaxy. (Abstract)

The consequences for other planetary systems are profound. Multiple planets beyond about 5 au (such as analogues of Jupiter, Saturn, Uranus and Neptune) may be common, but are so far unfortunately effectively hidden from detection by Doppler radial velocity and transit photometry techniques, the two most successful planet-finding techniques. If more distant, trans-Neptunian-like planets are also common, then the ingredients may exist to regularly generate instability and a frequently-changing dynamical environment during white dwarf phases of evolution. (14)

Villard, Ray. Is Earth One of a Kind? Astronomy. April, 2009. In just nine years since the gloomy premise of Ward and Brownlee’s Rare Earth: Why Complex Life is Uncommon in the Universe that a bioplanet with reflective sentience must be a vanishing improbability is in the process of being repealed. As this section documents, a galactic proliferation of solar systems with planets of every size and kind is now discovered. Among the recent revisions: Earth’s elements are not rare, a large moon is not critical, many stars are sun-like, life’s Cambrian burst is not a unique event, and so on.

Given the vast number of stars in our Milky Way, astronomers predict our galaxy may hold as many as one trillion planets. Even if one out of one million meets the above-described conditions, our galaxy would still contain at least one million Earth clones. (39)

Walker, Sara, et al. Exoplanet Biosignatures: Future Directions. arXiv:1705.08071. A 123 page summary paper for a 2016 workshop by this title (search) by a 14 member team including Leroy Cronin, William Bains, Betul Kacar, and Nancy Kiang. In regard, an intelligent Earthkinder begins to explore and quantify a fertile, galactic and cosmic milieu which innately fills itself with abundant evolutionary bioworlds. Many aspects and methods such as Bayesian statistics, geochemical environs, definitions of a universal biology, evolutionary essences, solar systems candidates, and so on, are considered.

Exoplanet science promises a continued rapid accumulation of new observations in the near future, energizing a drive to understand and interpret the forthcoming wealth of data to identify signs of life beyond our Solar System. The large statistics of exoplanet samples, combined with the ambiguity of our understanding of universal properties of life and its signatures, necessitate a quantitative framework for biosignature assessment Here, we introduce a Bayesian framework for guiding future directions in life detection, which permits the possibility of generalizing our search strategy beyond biosignatures of known life. The Bayesian methodology provides a language to define quantitatively the conditional probabilities and confidence levels of future life detection and, importantly, may constrain the prior probability of life with or without positive detection. We describe empirical and theoretical work necessary to place constraints on the relevant likelihoods, including those emerging from stellar and planetary context, the contingencies of evolutionary history and the universalities of physics and chemistry. We discuss how the Bayesian framework can guide our search strategies, including determining observational wavelengths or deciding between targeted searches or larger, lower resolution surveys. Our goal is to provide a quantitative framework not entrained to specific definitions of life or its signatures, which integrates the diverse disciplinary perspectives necessary to confidently detect alien life. (Abstract)

Wang, Haiyang, et al. The Elemental Abundances (with Uncertainities) of the Most Earth-like Planet. arXiv:1708.08718. As our collaborative humankinder proceeds to quantify the cosmos, Australian National University astrophysicists Wang, Charles Lineweaver, and Trevor Ireland contribute a geochemical assay of Earth’s material composition. Whom then are we curative creatures to appear as the universe’s way of learning this, and for what purpose?

To first order, the Earth as well as other rocky planets in the Solar System and rocky exoplanets orbiting other stars, are refractory pieces of the stellar nebula out of which they formed. To estimate the chemical composition of rocky exoplanets based on their stellar hosts' elemental abundances, we need a better understanding of the devolatilization that produced the Earth. To quantify the chemical relationships between the Earth, the Sun and other bodies in the Solar System, the elemental abundances of the bulk Earth are required. Here we present concordance estimates (with uncertainties) of the elemental abundances of the bulk Earth, which can be used in such studies. Our concordance estimates for the abundances of Mg, Sn, Br, B, Cd and Be are significantly lower than previous estimates of the bulk Earth. Our concordance estimates for the abundances of Na, K, Cl, Zn, Sr, F, Ga, Rb, Nb, Gd, Ta, He, Ar, and Kr are significantly higher. The uncertainties on our elemental abundances usefully calibrate the unresolved discrepancies between standard Earth models under various geochemical and geophysical assumptions. (Abstract excerpts)

Wang, Yun, et al. ATLAS Probe: Breakthrough Science of Galaxy Evolution, Cosmology, Milky Way, and the Solar System. arXiv:1802.01539. A 39 member international team posts an Astrophysics Telescope for Large Area Spectroscopy project concept for a NASA mission, circa 2030, to follow up the mid 2020s WFIRST Wide-Field Infrared Survey Telescope. As the quotes cite, we ought to appreciate how actually awesome is this grand humankinder endeavor. A sapient, collaborative species on a minute bioworld yet can embark forthwith to quantify any spatial and temporal breadth and depth of galactic, stellar, and material realms. But we are still not moved to ask what kind of a greater cosmic reality evolves toward and seems to require its own internal self-description. Whom are we brilliant beings summoned to do this, as if a genesis universe were trying to pass its future procreation to our intentional agency?

ATLAS Probe science spans four broad categories that address the five fundamental questions: (1) revolutionize galaxy evolution studies by tracing the relation between galaxies and dark matter from galaxy groups to cosmic voids and filaments, from the epoch of reionization through the peak era of galaxy assembly; (2) open a new window into the dark Universe by weighing the dark matter filaments in the cosmic web using 3D weak lensing, and obtaining definitive measurements of dark energy and tests of General Relativity using galaxy clustering; (3) probe the Milky Way’s dust-enshrouded regions, reaching the far side of our Galaxy; and (4) characterize Kuiper Belt Objects and other planetesimals in the outer Solar System. (3)

ATLAS Probe will be capable of transforming the state of knowledge of how the Universe works by the time it launches in ∼ 2030. (4) ATLAS is designed to watch galaxies emerge and grow within the cosmic web during the first half of cosmic history. ATLAS Probe is designed to reveal the detailed structure of the cosmic web. (7) TLAS Probe is a compelling mission concept for a NASA probe-class mission. It is a follow-up space mission to WFIRST; it multiplexes the scientific return of WFIRST by obtaining spectra of ∼90% of all galaxies imaged by the WFIRST High Latitude Survey at z> 0.5. Enabled by the mature DMD technology that allows a spectroscopic multiplex factor of 5,000 to 10,000, ATLAS Probe will lead to ground-breaking science over the entire range of astrophysics: from galaxy evolution to the dark Universe, from objects in the outer Solar System to the dusty regions of the Milky Way. (36)

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