Article
Multidisciplinary Sciences
William Bains, Janusz J. Petkowski, Paul B. Rimmer, Sara Seager
Summary: The atmosphere of Venus, particularly the chemistry within its cloud layers, presents many mysteries such as the presence of O-2, unknown compositions of large particles, and unusual abundance profiles of SO2 and H2O. This study proposes a hypothesis involving the presence of ammonia (NH3) which could explain these anomalies and suggest that Venus' clouds may be more habitable than previously thought. The hypothesis is based on existing observations and can be tested by future in situ measurements on Venus.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2021)
Article
Geochemistry & Geophysics
Peter M. Higgins, Christopher R. Glein, Charles S. Cockell
Summary: Research on the energy supply for potential hydrogenotrophic methanogens in Enceladus' subsurface ocean suggests that habitability depends on a delicate balance of factors including temperature, pH, and salinity. Further study of these parameters is needed to definitively assess habitability.
JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
(2021)
Article
Astronomy & Astrophysics
Robert J. Graham
Summary: The impact of CO2 on planetary temperature and ocean pH decreases with increasing pCO(2), resulting in smaller effects on high pCO(2) planets. Major CO2 disturbances on high pCO(2) planets in the outer habitable zone are likely to have mild or negligible impacts on surface temperature and ocean pH. The surface environment of the Phanerozoic Earth, with low pCO(2), may be unusually volatile compared to similar planets receiving lower insolation.
Article
Astronomy & Astrophysics
Rudy Arthur, Arwen Nicholson
Summary: When searching for inhabited exoplanets, understanding the boundaries of the habitable zone is crucial. The presence of life can influence these boundaries, as shown in a model that investigates the impact of life on temperature regulation. Despite the possibility of punctuations, where the system's equilibria can shift, the ensemble of systems tends to sustain or improve conditions for life, known as Entropic Gaia. This model also explores the concept of a Gaian habitable zone and provides insights into the Gaian bottleneck hypothesis and the habitability/inhabitance paradox.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Manasvi Lingam
Summary: The concept of habitable zone has a long history dating back to the 19th century, originating from geography and later generalized to include planetary habitability. The people involved in its development were numerous, but most of their musings remained nebulous, yet some true insights emerged during this period.
INTERNATIONAL JOURNAL OF ASTROBIOLOGY
(2021)
Article
Geochemistry & Geophysics
Matthew A. Pasek, Arthur Omran, Tian Feng, Maheen Gull, Carolyn Lang, Josh Abbatiello, Lyle Garong, Ray Johnston, Jeffrey Ryan, Heather Abbott-Lyon
Summary: Phosphorus is not limited to existing solely as phosphate, but can also exist as phosphite in extremely reducing environments. By studying the speciation of phosphorus in serpentinite rocks and muds, researchers have found that phosphate can be reduced to phosphite. The study suggests that under low redox conditions, this transformation may release more phosphite, providing a key nutrient for life.
GEOCHIMICA ET COSMOCHIMICA ACTA
(2022)
Article
Astronomy & Astrophysics
Noam R. Izenberg, Diana M. Gentry, David J. Smith, Martha S. Gilmore, David H. Grinspoon, Mark A. Bullock, Penelope J. Boston, Grzegorz P. Slowik
Summary: Ancient Venus and Earth may have had similar conditions necessary for the development of life, with the possibility that life originated on Venus and has survived through time. The Venus Life Equation introduces a new method for calculating the probability of life on Venus, highlighting areas for future exploration missions to address.
Article
Astronomy & Astrophysics
R. Spinelli, F. Borsa, G. Ghirlanda, G. Ghisellini, F. Haardt
Summary: The rocky exoplanets discovered in the circumstellar habitable zone (CHZ) are currently the most suitable places for hosting life outside the Solar system. However, the presence of liquid water on these CHZ planets does not guarantee habitable environments for the emergence of life. Experimental studies suggest that the building blocks of life are likely produced photochemically in the presence of a minimal ultraviolet (UV) flux. High UV flux, on the other hand, can be detrimental to life. This raises questions about the habitability of CHZ planets around stars with different UV to bolometric luminosity ratios. By combining the principle of mediocrity and recent experimental studies, the researchers define UV boundary conditions within which life can possibly emerge and evolve. They analyze data from the Swift-UV/Optical Telescope and find that most of the CHZ exoplanets actually orbit outside the UV-habitable zone, where the NUV luminosity of their M-dwarf hosts is too low to trigger abiogenesis.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Engineering, Aerospace
Rachana Agrawal, Weston P. Buchanan, Archit Arora, Athul P. Girija, Maxim De Jong, Sara Seager, Janusz J. Petkowski, Sarag J. Saikia, Christopher E. Carr, David H. Grinspoon, James M. Longuski
Summary: This article introduces a mission concept to explore the clouds of Venus in order to evaluate habitability and search for signs of life. A super-pressure variable float altitude balloon aerobot is proposed to cycle between different cloud layers and transmit data through an orbiter relay. The mission, scheduled for 2026, aims to complement other planned missions and shed light on the limits of habitability and the role of unknown chemistry or possibly life itself in the Venus atmosphere.
Article
Astronomy & Astrophysics
Vera Dobos, Andras Haris, Inga E. E. Kamp, Floris F. S. van der Tak
Summary: This study investigates the habitability of hypothetical moons orbiting known exoplanets. It calculates the incident stellar radiation and tidal heating flux to determine habitability. Based on the results, a target list of exoplanets with a high probability of hosting habitable moons is provided.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Biology
Adriana C. Gomez-Buckley, Gordon M. Showalter, Michael L. Wong
Summary: The study of extreme environments on Earth helps in the search for life in the universe. Recent research has focused on the role of viruses in terrestrial ecosystems and their potential significance in extraterrestrial environments. This study proposes a mechanism called the 'viral elevator' which suggests that viruses can transport dissolved organic matter to a hypothetical sub-ice biosphere on Jupiter's moon Europa. This has implications for future exploration of life on Europa.
Article
Engineering, Aerospace
Sara Seager, Janusz J. Petkowski, Christopher E. Carr, Sarag J. Saikia, Rachana Agrawal, Weston P. Buchanan, David H. Grinspoon, Monika U. Weber, Pete Klupar, Simon P. Worden, Iaroslav Iakubivskyi, Mihkel Pajusalu, Laila Kaasik
Summary: Scientists have been considering the potential existence of life in the clouds of Venus for over half a century. In situ atmospheric measurements using modern instruments can determine whether the cloud decks have the necessary characteristics to support life. A suite of instruments is proposed to measure the acidity, water content, presence of metals, organic material, and biosignature gases in the droplets. The mission also serves as preparation for sample return by studying the non-liquid cloud particles and informing collection and storage methods.
Article
Astronomy & Astrophysics
Giovanni Covone, Riccardo M. Ienco, Luca Cacciapuoti, Laura Inno
Summary: The study evaluates the possibility of oxygenic photosynthesis on planets around stars based on their spectral type and planet-star separation, finding that exergy increases with star effective temperature and biospheres on exoplanets around cool stars may be light-limited. Terrestrial planets comparable to Earth in terms of useful photon flux, exergy, and exergetic efficiency have not yet been observed.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
J. J. Bernal, C. D. Sephus, L. M. Ziurys
Summary: Observations of methanol in molecular clouds in the outer Galaxy reveal that these clouds are cold and dense, with methanol abundances comparable to those in colder molecular clouds in the solar neighborhood. The abundance of methanol does not significantly decrease with distances from the Galactic Center, indicating that organic chemistry is prevalent in the outer Galaxy and may help assess the Galactic Habitable Zone.
ASTROPHYSICAL JOURNAL
(2021)
Article
Geochemistry & Geophysics
Benjamin M. Tutolo, Nicholas J. Tosca
Summary: Alkaline lakes are unique and fascinating biogeo-chemical environments that have remained distinctive features of Earth's evolving surface. Understanding these lakes requires an interdisciplinary approach at the intersection of hydrology, geology, and biology. The articles in this issue evaluate the characteristics and importance of alkaline lakes in unraveling Earth's history and habitability on ancient Mars, hoping to attract more interest in these environments.