Comparison Of Formation, Atmosphere and Habitability for Mercury and Venus
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The solar system has very strong relationship with human. All the factors in it creates the distinctive circumstances for all life on Earth to survive. This study picks two planets in the solar system, i.e., Mercury and Venus, to discuss and compare on three features from the perspective of formation, atmosphere and habitability. According to the analysis, either planet is suitable for life’s existence or human’s residence based on the state-of-art techniques. To be specific, Mercury’s formation is still a problem to be solved while Venus’ is much clearer. Venus’ thicker atmosphere contains CO2, N2 and sulfuric chemicals as well as PH3, an indicator for the improbable life. Mercury’s atmosphere is rather poor, but is important partly because it can offer information of the planet’s formation. This article can help beginners obtain an understanding about two planets’ features in three aspects and aid students on similar topics. Overall, these results shed light on guiding further exploration of solar system.Keywords:
Habitability
Mercury
Atmosphere of Venus
Planetary habitability
The recent discovery of a staggering diversity of planets beyond the Solar System has brought with it a greatly expanded search space for habitable worlds. The Kepler exoplanet survey has revealed that most planets in our interstellar neighborhood are larger than Earth and smaller than Neptune. Collectively termed super-Earths and mini-Neptunes, some of these planets may have the conditions to support liquid water oceans, and thus Earth-like biology, despite differing in many ways from our own planet. In addition to their quantitative abundance, super-Earths are relatively large and are thus more easily detected than true Earth twins. As a result, super-Earths represent a uniquely powerful opportunity to discover and explore a panoply of fascinating and potentially habitable planets in 2020 - 2030 and beyond.
Planetary habitability
Kepler-69c
Habitability
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The discovery of seven Earth-sized planets around the ultracool dwarf star TRAPPIST-1 in 2017 brought a new type of planetary system to our attention. Modelling the planets of this system and considering new physical processes may result in a more realistic description of those exoplanets that are considered to be the most habitable ones. Similar planetary systems to the TRAPPIST-1 are expected to be discovered with current and upcoming missions, and in fact, recently, two Earth-sized planet candidates were announced around the ultracool Teegarden's Star (Zechmeister et al. 2019). Detailed modelling of similar exoplanetary systems will be an important task to reveal their astrobiological potential. Until new discoveries, the TRAPPIST-1 system serves as a prototype of an ultracool M dwarf with a planetary system of Earthlike planets. For this reason, studying the TRAPPIST-1 planetary system is a pioneering work that will help in the characterization of similar systems that are yet to be discovered.The habitability of Earth-like exoplanets around M dwarfs is becoming the forefront of exoplanetary research as the TRAPPIST-1 system is recently in the centre of attention. Tidal heating may be an important effect influencing habitability, especially for close-in planets or moons. Close-in bodies quickly become tidally locked, but if their eccentricities are excited by periodic perturbing effects of other planets or moons in the system, then varying tidal forces keep causing friction inside the body that leads to continuous heat generation (Peale et al. 1979). Some studies suggest that tidal heating may enable the emergence of life in otherwise too cold environments (Scharf 2006, Dobos & Turner 2015, Forgan & Dobos 2016, Dobos et al. 2017).Using a Maxwell viscoelastic rheology, we computed the tidal response of the planets using the volume-weighted average of the viscosities and rigidities of the metal, rock, high-pressure ice, and liquid water/ice I layers. After determining the possible interior structures, we computed the heat flux due to stellar irradiation and tidal heating for the inner four planets (Barr et al. 2018, Dobos et al. 2019). We found that planet e is the most likely to support a habitable environment, with Earth-like surface temperatures and possibly liquid water oceans. Planet d also avoids a runaway greenhouse state (in which it would irreversibly lose all of its surface water content), if its surface reflectance is at least as high as that of the Earth. Planets b and c have heat fluxes high enough to trigger a runaway greenhouse and to support volcanism on the surfaces of their rock layers. Planets f, g, and h do not experience significant tidal heating arising from the star, and likely have solid ice surfaces with possible subsurface liquid water oceans.We also connected dynamic evolution of planetary orbits with interior structure considerations for the inner two TRAPPIST-1 planets (Brasser et al., 2019). Based on stability considerations, and with the assumption that orbital resonances are lasting for planets b and c, lower limits can be determined for their k2/Q tidal parameter. This parameter can further be constrained by the planets' interior structure which determines their tidal dissipation. Although the two approaches gave different results, well-constrained tidal parameters will improve the realism of orbital evolution simulations including tidal effects.
Habitability
Planetary habitability
Outer planets
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Here, we propose a Venus exploration program designed to explain the origin and divergent evolution of the interiors, surfaces, and atmospheres of the terrestrial planets in our solar system, and provide greater insight into the conditions that may affect the habitability of terrestrial planets in other solar systems.
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Atmosphere of Venus
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We present a case for the exploration of Venus as an astrobiology target-(1) investigations focused on the likelihood that liquid water existed on the surface in the past, leading to the potential for the origin and evolution of life, (2) investigations into the potential for habitable zones within Venus' present-day clouds and Venus-like exo atmospheres, (3) theoretical investigations into how active aerobiology may impact the radiative energy balance of Venus' clouds and Venus-like atmospheres, and (4) application of these investigative approaches toward better understanding the atmospheric dynamics and habitability of exoplanets. The proximity of Venus to Earth, guidance for exoplanet habitability investigations, and access to the potential cloud habitable layer and surface for prolonged in situ extended measurements together make the planet a very attractive target for near term astrobiological exploration.
Habitability
Planetary habitability
Atmosphere of Venus
Atmospheric escape
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We present a case for the exploration of Venus as an astrobiology target—(1) investigations focused on the likelihood that liquid water existed on the surface in the past, leading to the potential for the origin and evolution of life, (2) investigations into the potential for habitable zones within Venus' present-day clouds and Venus-like exo atmospheres, (3) theoretical investigations into how active aerobiology may impact the radiative energy balance of Venus' clouds and Venus-like atmospheres, and (4) application of these investigative approaches toward better understanding the atmospheric dynamics and habitability of exoplanets. The proximity of Venus to Earth, guidance for exoplanet habitability investigations, and access to the potential cloud habitable layer and surface for prolonged in situ extended measurements together make the planet a very attractive target for near term astrobiological exploration.
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Planetary habitability
Atmosphere of Venus
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Illustrated with breathtaking images of the Solar System and of the Universe around it, this book explores how the discoveries within the Solar System and of distant exoplanets come together to aid understanding of the habitability of Earth, and how this guides the search for exoplanets that could support life. The author recounts how, within two decades of the discovery of the first planets outside the Solar System in the 1990s, scientists concluded that planets are so common that most stars are orbited by them. The twelve chapters highlight what we have learned about exoplanets and how the lives of exoplanets and their stars are inextricably interwoven. Stars are the seeds around which planetary systems form. Stars provide their planets with light and warmth for as long as they shine. At the end of their lives, stars expel massive amounts of newly forged elements into deep space. That ejected material is incorporated into subsequent generations of planets. How do we learn about these distant worlds? What does the exploration of other planets tell us about the history of Earth? Can we find out what the distant future may have in store for us? What do we know about exoworlds and starbirth, and where do migrating hot Jupiters, polluted white dwarfs, and free-roaming nomad planets fit in? What does all that have to do with the habitability of Earth and the possibility of finding extraterrestrial life? And how did the globe-spanning network of the sciences begin to answer all these questions?
Habitability
Extraterrestrial Life
Planetary habitability
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Significance The search for exoplanets has rapidly emerged as one of the most important endeavors in astronomy. This field received a major impetus with the recent discovery of seven temperate Earth-sized exoplanets orbiting the nearby ultracool dwarf star TRAPPIST-1. One of the most crucial requirements for conventional (surface-based) planetary habitability is the presence of an atmosphere over long timescales. We determine the atmospheric escape rates numerically and analytically for the planets of the TRAPPIST-1 system and show that the outer planets are potentially likely to retain their atmospheres over billion-year timescales. Our work has far-reaching and profound implications for atmospheric escape and the habitability of terrestrial exoplanets around M dwarfs.
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Ancient rivers and lakes discovered on Mars. Numerous temperate, Earth-sized exoplanets detected around nearby stars. Thanks to ground and space-based telescope observations and Solar System exploration missions, we now have a fantastic playground to explore how prevalent life is in the Universe. The main goal of my thesis work is to better understand the conditions necessary for a planet to maintain liquid water - a primary building block for life - on its surface. Using 3-D numerical climate models, as well as spectroscopic calculations and measurements, I conducted two major investigations during my thesis. First, I explored the environments of ancient Mars at multiple epochs in order to understand the conditions in which the enigmatic Martian rivers were carved. Apart from Earth, Mars is the only planet that has been habitable, but we don't know why. I showed that extreme events (outflow channel formation, meteoritic impacts) that scarred the surface of Mars cannot explain the formation of these valley networks. Nonetheless, I showed that the presence of reducing greenhouse gases such as hydrogen and methane offers a promising alternative solution. Secondly, I studied the possible atmospheres of solid, temperate exoplanets, with a particular focus on those orbiting small stars such as Proxima Centauri and TRAPPIST-1. I showed that some of these planets have characteristics that are highly favourable to the presence of liquid water on their surface. This result is really promising as it will be soon become possible - as demonstrated in my thesis for Proxima b - to characterize the atmosphere of these planets with the future JWST and ELTs astronomical observatories.
Habitability
Planetary habitability
Kepler-69c
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The search for exoplanets includes the promise to eventually find and identify habitable worlds. The thousands of known exoplanets and planet candidates are extremely diverse in terms of their masses or sizes, orbits, and host star type. The diversity extends to new kinds of planets, which are very common yet have no solar system counterparts. Even with the requirement that a planet's surface temperature must be compatible with liquid water (because all life on Earth requires liquid water), a new emerging view is that planets very different from Earth may have the right conditions for life. The broadened possibilities will increase the future chances of discovering an inhabited world.
Habitability
Planetary habitability
Liquid water
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