III. Ecosmos: A Revolutionary Fertile, Habitable, Solar-Bioplanet, Incubator Lifescape
H. Stellar Planetary Systems: A Stochastic Profusion of Galaxies, Solar Orrerys, and Habitable Zones
Elser, Sebastian, et al. How Common are Earth-Moon Planetary Systems? Icarus. 214/2, 2011. In Rare Earth (2000) Peter Ward and Donald Brownlee say that a planet with a large moon is helpful for life to evolve, but worry that the system would be statistically unusual. Drawing on a decade of celestial advances, University of Zurich and University of Colorado astrophysicists now contend that such couplings are much more common. Indeed, along with many other findings, the Ward and Brownlee case has been largely refuted. On the contrary, our galaxy and the whole cosmos seems made to innately seed itself with conducive bioearths.
The Earth’s comparatively massive moon, formed via a giant impact on the proto-Earth, has played an important role in the development of life on our planet, both in the history and strength of the ocean tides and in stabilizing the chaotic spin of our planet. Here we show that massive moons orbiting terrestrial planets are not rare. A large set of simulations by Morishima et al. (Morishima, R., Stadel, J., Moore, B. . Icarus. 207, 517–535), where Earth-like planets in the habitable zone form, provides the raw simulation data for our study. We use limits on the collision parameters that may guarantee the formation of a circumplanetary disk after a protoplanet collision that could form a satellite and study the collision history and the long term evolution of the satellites qualitatively. We find that giant impacts with the required energy and orbital parameters for producing a binary planetary system do occur with more than 1 in 12 terrestrial planets hosting a massive moon, with a low-end estimate of 1 in 45 and a high-end estimate of 1 in 4. (Abstract, 357)
Emsenhuber, Alexandr, Alexandre, et al. Planetary Population Synthesis and the Emergence of Four Classes of Planetary System Architectures. arXiv:2303.00012. We note this work by Ludwig-Maximilians-Universit, University of Bern, and MPI Astronomie exo-researchers as another example of new perceptions of how solar systems seem to have an array of overall properties.
Here, we review the population synthesis method to explore which conditions lead to different planetary system architectures. As a result, we identify four main groups: a near-in situ compositionally ordered terrestrial and ice planets, migrated sub-Neptunes, mixed low-mass and dynamically active giants without inner low-mass planets. These four classes exhibit typical formation pathways and are certain mass scales. The breakdown into classes allows to better understand which physical processes are dominant. Comparison with observations reveals certain differences to the actual population, pointing at limitation of theoretical understanding. (Excerpt)
Fields, Benjamin, et al. Information Gain as a Tool for Assessing Biosignature Missions. International Journal of Astrobiology. July, 2023. Blue Marble Space Institute of Science researchers BF, Sohom Gupta and McCullen Sandora propose a better, systematic approach as we Earthlings embark on a near and farther celestial census to bravely seek out, evaluate potential neighbors. Hello. is anyone there?
We propose the mathematical notion of information gain as a way to best assess the value of biosignature searches. This approach applies to many case examples: the minimal number of samples to see a trend in signal occurrence rate as a function of an environmental variable, and how much cost to allocate to aspect; false positives and false negatives, tradeoffs between resolution and coverage; how to deduce a habitability boundary; and much more. In each case, we state quantitative, optimum recommendations for mission design, selection, and/or target choice. (Excerpt)
Fischer, Debra. Early Start for Rocky Planets. Nature. 486/331, 2012. The Yale University astronomer reviews a Letter in this issue “An Abundance of Small Exoplanets around Stars with a Wide Range of Metallicities” by Lars Buchhave, et al, a large team from Copenhagen, NASA and California. They find the chemical composition of stars which host smaller planets to be more varied than those with larger planets. This result is seen to favor an earlier start and prevalence for more earth-like worlds.
Fisher, Theresa, et al.. A Complex Systems Approach to Exoplanet Atmospheric Chemistry: New Prospects for Ruling Out the Possibility of Alien Life-As-We-Know-It. arXiv:2310.05359. Arizona State University astrobiologists TF, Estelle Janin and Sara Walker post a latest comprehensive review as Earthumanity prepares to seek and rightly identify near and further occasions of inhabited exoworlds. A segment wonders over how to evaluate what evolutionary stage they may have reached, with attention to global civilizations. The especial contribution herein is a novel notice of life’s multiplex anatomy and physiology as vital indicators. See also PyATMOS: A Scalable Grid of Hypothetical Planetary Atmospheres by Aditya Chopra, et al at 2308.10624; and Fully fluorinated non-carbon compounds NF3 and SF6 as technosignature gases by Sara Seager, et al at 2308.13667 for other studies.
The near-term capability to characterize terrestrial exoplanet atmospheres may bring us closer to discovering alien life. However, detectable candidate biosignature gases are subject to false positives that can be produced abiotically. To distinguish, we take a complex systems approach using a chemical reaction network analysis of planetary atmospheres. Network properties like mean degree and shortest path length can effectively display when CH4 is produced from methanogenesis and serpentinization. Our results confirm how a network theoretic approach can clearly specify biological, abiotic and anomalous atmospheres. (Excerpt)
Folger, Tim. The Planet Boom. Discovery. May, 2011. One of many post-Kepler satellite reports trying to convey this awesome discovery of an innately world-seeding, gravid cosmos. Per the quote, our earth can be known as far from rare. By any measure galaxies will be filled with solar systems, which seem to proliferate in every imaginable variety. And as Bill Borucki, for many years NASA’s champion of the Kepler mission, comments, this fantastic vista brings a profound significance to earth’s stirring ability via humankind to learn and decide to succeed.
For the first time, we have a handle on the odds, and the numbers beaming in from Kepler are not only encouraging but staggering. “Our galaxy contains 200 billion stars,” (Geoffrey) Marcy says, “I would guess that at least 30 percent of them have an earth-size planet. So 30 percent of 200 billion, that’s at least 60 billion Earth-size planets just in our galaxy alone.” (33)
Franck, Siegfried, et al. Extraterrestrial Gaias. Schneider, Stephen, et al, eds. Scientists Debate Gaia. Cambridge: MIT Press, 2004. The detection of extrasolar, earth-like planets takes on a new dimension when viewed through the lens of the Gaia perspective. Whether they are life-bearing can be ascertained by the composition of their atmosphere.
The general question is whether an Earth-sized planet discovered outside the solar system can accommodate a self-regulating geosphere-biosphere system with homeorrhesis (i.e., sister of Gaia). (315)
Frank, Adam. How Nature Builds a Planet. Discover. July, 2005. The latest info on varieties of planetary formation as an intelligent earth learns about its own origin and those of its neighbors.
Gaidos, Eric, et al. New Worlds on the Horizon: Earth-Sized Planets Close to Other Stars. Science. 318/210, 2007. We are presently witness to a unique historical achievement, not imaginable any time sooner, when our sentient planet via telescope, satellite, and computer instrumentation, along with a global research network, can detect a plethora of kindred orbs around other stars throughout the galaxy. What then is an ovular bioplanet of which we should be mindful? Might human beings at once ‘therefore choose Earth’, and seek to begin a celestial conversation?
Gargaud, Muriel, et al. Habitability in the Universe from the Early Earth to Exoplanets. Origins of Life and Evolution of Biospheres. 46/4, 2016. An introduction to a special issue as a profligate cosmic vista opens to us Earthlings. Typical papers are Host Star Evolution for Planet Habitability, Review on the Role of Planetary Factors on Habitability, and The Logic of Life by Robert Pascal and Addy Pross, abstract below.
In this paper we propose a logical connection between the physical and biological worlds, one resting on a broader understanding of the stability concept. We propose that stability manifests two facets - time and energy, and that stability’s time facet, expressed as persistence, is more general than its energy facet. That insight leads to the logical formulation of the Persistence Principle, which describes the general direction of material change in the universe, and which can be stated most simply as: nature seeks persistent forms. Significantly, the principle is found to express itself in two mathematically distinct ways: in the replicative world through Malthusian exponential growth, and in the ‘regular’ physical/chemical world through Boltzmann’s probabilistic considerations. By encompassing both ‘regular’ and replicative worlds, the principle appears to be able to help reconcile two of the major scientific theories of the 19th century – the Second Law of Thermodynamics and Darwin’s theory of evolution – within a single conceptual framework. (Pascal, Pross)
Gaudi, B. Scott, et al. The Demographics of Exoplanets. arXiv:2011.04703. SG, Ohio State University, Jessie Christiansen, Caltech, and Michael Meyer, University of Michigan post a chapter to appear in ExoFrontiers: Big Questions in Exoplanetary Science (Bristol: IOP Publishing Ltd) AAS-IOP ebooks, 2021). It is a sign of a new maturity if this fast-moving, expansive field of exoplanetary science can begin to lay out a program for a near and farther census. Amongst many aspects are the shape of the explanet, host star interactions, multiple formation paths for gas giants, and so on. But as the second quote notes, these studies come up with more evidence of how special our own Sun – Earth system really is.
In the broadest sense, the primary goal of exoplanet demographic surveys is to determine the frequency and distribution of planets as a function of as many of the physical parameters that may influence planet formation and evolution as possible, over as broad of a range of these parameters as possible. By comparing these planet distributions to the predictions of planet formation theories, we can begin to both test and refine these theories. In this chapter, we review the major results on exoplanet demographics to date. (Abstract)
Gaudi, B. Scott, et al. The Habitable Exoplanet Observatory Mission Concept Report. arXiv:2001:06683. We note this 500 page mission statement by some 200 astroscientists with a main base at Jet Propulsion Laboratory as a premier example into the 2030s of our collaborative Earthkind personsphere beginning to explore, quantify and spread forth in a revolutionary genesis universe.