Special Issue "Planetary Evolution and Search for Life on Habitable Planets"

A special issue of Geosciences (ISSN 2076-3263). This special issue belongs to the section "Biogeosciences".

Deadline for manuscript submissions: 1 March 2019

Special Issue Editors

Guest Editor
Prof. Dr. Lena Noack

Department of Earth Sciences, Free University of Berlin, Malteserstrasse 74-100, D-12249, Berlin, Germany
Website | E-Mail
Interests: mantle convection; planetary habitability; astrobiology; planet evolution; mineralogy; outgassing; plate tectonics; volatile cycles
Guest Editor
Dr. Ralf Moeller

German Aerospace Center (DLR e.V.), Institute of Aerospace Medicine, Radiation Biology Department, Space Microbiology Research Group, Bldg. 24m/R. 139, Linder Hohe, D-51147 Cologne (Köln), Germany
Website | E-Mail
Interests: space life science; astrobiology; biosignatures; extremophiles; radiation; extraterrestrial conditions; search/origin/evolution of life

Special Issue Information

Dear Colleagues,

This Special Issue aims at bringing together studies from different research fields of astrobiology, that are related to the questions of habitability of planets and moons and the search for life both in our solar system and beyond.

Earth is the only planet that we know of so far, which is inhabited by life. Our neighbour planets Mars and Venus lack proof of extinct or extant life, and are examples of at least partly uninhabitable worlds for life as we know it. With more and more exoplanets being discovered in the right distance to their host stars, such that these planets could have liquid water—and hence Earth-like life—at their surface, it is increasingly important to understand what factors make a planet habitable, and what influences not only origin but also distribution, evolution and survival of life.

We invite both review papers as well as original research papers from all subfields of astrobiology with the focus on planetary habitability within and outside the solar system. This includes for example conceptual studies on habitability of planets or niches, models of the interactions evolving between planet and life with its signatures, as well as space life science studies to understand the limits of Earth-like life.

It is recommended to submit a short letter of intent with information on title, authors, and a short description of the planned paper at least two months before the submission deadline to the guest editors in order to verify if the paper matches the scope of the special issue.

Prof. Dr. Lena Noack
Dr. Ralf Moeller
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Geosciences is an international peer-reviewed open access monthly journal published by MDPI.

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Keywords

  • planetary habitability
  • exoplanets
  • astrobiology
  • search for life
  • biosignatures
  • spaceflight missions and technologies
  • origin/evolution/distribution of life
  • extremophiles/microbiology

Published Papers (3 papers)

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Research

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Open AccessCommunication Survival of Radioresistant Bacteria on Europa’s Surface after Pulse Ejection of Subsurface Ocean Water
Received: 26 November 2018 / Revised: 19 December 2018 / Accepted: 21 December 2018 / Published: 25 December 2018
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Abstract
We briefly present preliminary results of our study of the radioresistant bacteria in a low temperature and pressure and high-radiation environment and hypothesize the ability of microorganisms to survive extraterrestrial high-radiation environments, such as the icy surface of Jupiter’s moon, Europa. In this [...] Read more.
We briefly present preliminary results of our study of the radioresistant bacteria in a low temperature and pressure and high-radiation environment and hypothesize the ability of microorganisms to survive extraterrestrial high-radiation environments, such as the icy surface of Jupiter’s moon, Europa. In this study, samples containing a strain of Deinococcus radiodurans VKM B-1422T embedded into a simulated version of Europa’s ice were put under extreme environmental (−130 °C, 0.01 mbar) and radiation conditions using a specially designed experimental vacuum chamber. The samples were irradiated with 5, 10, 50, and 100 kGy doses and subsequently studied for residual viable cells. We estimate the limit of the accumulated dose that viable cells in those conditions could withstand at 50 kGy. Combining our numerical modelling of the accumulated dose in ice with observations of water eruption events on Europa, we hypothesize that in the case of such events, it is possible that putative extraterrestrial organisms might retain viability in a dormant state for up to 10,000 years, and could be sampled and studied by future probe missions. Full article
(This article belongs to the Special Issue Planetary Evolution and Search for Life on Habitable Planets)
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Review

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Open AccessReview A More Comprehensive Habitable Zone for Finding Life on Other Planets
Geosciences 2018, 8(8), 280; https://doi.org/10.3390/geosciences8080280
Received: 13 June 2018 / Revised: 25 July 2018 / Accepted: 26 July 2018 / Published: 28 July 2018
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Abstract
The habitable zone (HZ) is the circular region around a star(s) where standing bodies of water could exist on the surface of a rocky planet. Space missions employ the HZ to select promising targets for follow-up habitability assessment. The classical HZ definition assumes [...] Read more.
The habitable zone (HZ) is the circular region around a star(s) where standing bodies of water could exist on the surface of a rocky planet. Space missions employ the HZ to select promising targets for follow-up habitability assessment. The classical HZ definition assumes that the most important greenhouse gases for habitable planets orbiting main-sequence stars are CO2 and H2O. Although the classical HZ is an effective navigational tool, recent HZ formulations demonstrate that it cannot thoroughly capture the diversity of habitable exoplanets. Here, I review the planetary and stellar processes considered in both classical and newer HZ formulations. Supplementing the classical HZ with additional considerations from these newer formulations improves our capability to filter out worlds that are unlikely to host life. Such improved HZ tools will be necessary for current and upcoming missions aiming to detect and characterize potentially habitable exoplanets. Full article
(This article belongs to the Special Issue Planetary Evolution and Search for Life on Habitable Planets)
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Other

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Open AccessHypothesis The Rise of A Habitable Planet: Four Required Conditions for the Origin of Life in the Universe
Geosciences 2019, 9(2), 92; https://doi.org/10.3390/geosciences9020092
Received: 11 December 2018 / Revised: 19 January 2019 / Accepted: 11 February 2019 / Published: 16 February 2019
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Abstract
The advanced version of the author’s inversion concept of the origin of terrestrial life and its application for life in the Universe has been substantiated. A key step in the transition to life consists in the thermodynamic inversion of non-living prebiotic microsystems when [...] Read more.
The advanced version of the author’s inversion concept of the origin of terrestrial life and its application for life in the Universe has been substantiated. A key step in the transition to life consists in the thermodynamic inversion of non-living prebiotic microsystems when the contributions of free energy (F) and information (I) become prevalent over the contribution of entropy (S). It is based the thermodynamic corridor that is mandatory for all chemical scenarios for the origin of life: F + I < S (prebiotic microsystem) → F + I ≈ S (intermediate stage, inversion moment) → F + I > S (primary living unit). A prebiotic organic microsystem can reach the intermediate state between non-life and life only under high-frequency and multilevel oscillations of physic-chemical parameters in hydrothermal environments. The oscillations are considered the fourth required condition for the origin of life, in addition to the three well-known ones: the availability of organic matter, an aqueous medium, and a source of energy. The emergence of initial life sparks in nonequilibrium prebiotic microsystems (being at the intermediate state) proceeds through the continuous response (counteraction) of prebiotic microsystems to incessant physic-chemical oscillations (stress). The next step of laboratory simulations on the origin of life directed to the exploration of the microsystems’ response to high-frequency oscillations (>10−10 s–<30 min) is proposed. Finally, some fragments of the general scenario of the origin of life in the Universe based on the whole four required conditions have been outlined. Full article
(This article belongs to the Special Issue Planetary Evolution and Search for Life on Habitable Planets)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Planned paper 1:

Title: Diversity of microbial communities in Mars analog field sites on Iceland

Thorsten Stoeck1,*, Sabine Filker 2, René Groben 3, Viggó Marteinsson 3

  1. University of Technology Kaiserslautern, Ecology Group, Germany
  2. University of Technology Kaiserslautern, Molecular Ecology Group, Germany,
  3. Matís, Iceland

Abstracts: Several on-going and planned space missions are focused on the search for extinct or extant life on Mars. A better knowledge of the biology of field sites that are analogues to extraterrestrial bodies is essential to better understand whether life existed and exists beyond Earth, and how it could be detected if it does. Hydrothermal areas on Iceland are among the field sites, which have a high relevance to assess the possibility of past habitability of Mars: acid-sulfate fumarolic alteration are likely explanations for various geochemical and mineralogical features in Martian hydrothermal vent environments at areas such as Gusev Crater, Nili Fossae and Mawrth Vallis. Such conditions prevail for example in the Krýsuvík hydrothermal area. A similar, but much younger system is the Hveragerdi hot spring field site with its several pools differing in redox-conditions, pH values and temperature. In this area, even the rare neutral to alkaline sulfide-rich pools exist. Using state-of-the-art molecular tools (eDNA metabarcoding) and community statistical analyses, we investigated microbial communities of the Krysuvik and Hveragerdi geothermal fields. Microbial communities were unexpectedly diverse but vastly different in the investigated habitats. Protistan communities grouped in two larger distinct clusters, one of which including sampling sites from the Krysuvik field and one from the Hveragerdi field. The field-specific geothermal area properties were responsible for community structuring, showing that different geothermal fields support notably distinct communities. Bacterial communities clustered in different patterns, suggesting that bacterial and protistan communities are structured by different environmental drivers and/or physiological adaptations. Network analyses identified an extraordinary high degree of taxonomic novelty in all communities analysed, holding new genera, families and most likely even new orders and classes. Such organisms may be ideal candidates for further exploration of cellular adaptations of extremophiles thriving in Mars analog habitats.

Planned paper 2:

Title: Arising of a habitable planet: four required conditions for the origin of life

Vladimir Kompanichenko

Institute for Complex Analysis, Birobidzhan, Russia

Abstracts: There are three well-known conditions for the origin of life: availability of organic matter, aqueous medium, and source of energy. However, these conditions are insufficient to produce initial life because they do not take into consideration the fundamental distinction between a chemical and biological system. By now there are not experiments, which were carried out with using of these conditions and resulted in obtaining of primary life forms. According to the elaborated inversion concept (Kompanichenko 2017), the transition of organic microsystems into primary forms of life demands thermodynamic inversion, i.e. the kind of transformation that allows the systems to begin continuously concentrate free energy and information prevalent over entropy. Such transformation is possible only under incessant pressing on prebiotic microsystems due to oscillations of external physic-chemical parameters. The pressing launches active counteraction in the microsystems initiating appearance of initial sparks of life them. So, necessity of the multilevel oscillations in the medium can be considered as the fourth required condition for the origin of life. The fourth condition is usual in hydrothermal systems on Earth; besides, it corresponds to the conditions on satellites Enceladus and Europa, as well as on early Mars. To verify this approach, future experiments on prebiotic chemistry should be conducted under oscillating conditions modeling hydrothermal environments.

Planned paper 3:

Title: Atmospheric entry model for white soft mineral micrometeoroids in the context of Astrobiology

Gaia Micca Longo 1, Michał Gryga 2, Stanislav Horák 2, Viviana Piccinni 1, Savino Longo 1,3,4

  1. Department of Chemistry, Università degli studi di Bari Aldo Moro, Via Orabona 4, Bari, Italy
  2. Brno University of Technology, Antonínská 548/1, 601 90 Brno (Czech Republic)
  3. CNR-Nanotec, via Amendola 122/D, Bari 70126, Italy
  4. INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, Firenze I-50125, Italy

Abstracts: One of the most exciting perspectives in astrobiology is that the molecules discovered in space, and possibly others still undiscovered, may have had a very important role on the Earth’s chemical evolution and even in the origin of life on Earth. An important stage of any scenario evaluating this perspective is the so-called delivery, i.e. the actual transport of molecules from space to Earth. Given the high relative speed involved in the atmospheric entry process of meteoroids that might act as carriers (not less than the escape speed from Earth, 11.2 km/s), some protection must have been provided to the organic fraction possibly embedded in these thermally resistant bodies. These bodies must be of the optimal size and grains in the range 0.01-1 mm appear to grant the highest transfer rate. We present an atmospheric entry model for micrometeoroids with evaporitical composition (i.e. Mg-, Ca-, Fe- carbonates and Ca sulphates), as these minerals have been widely detected in Space and are often associated with life forms. The model includes a 2D geometry, the real non isothermal atmospheric profile, power balance, evaporation, ablation, radiation losses; furthermore, it includes additional features like chemical changes, stoichiometry, chemical effects in the power balance. Several thermal curves will be plotted, in order to focus on the thermal history of different entry scenarios; furthermore, thanks to a Monte Carlo implementation, histograms will focus on the actual fractions of carbonates and sulphates that are able to reach the Earth’s surface. Results will show that sub-millimeter evaporitical grains are potentially effective organic matter carriers.

Planned paper 4:

Title: Kinetics of White Soft Minerals (WSMs) Decomposition under Conditions of Interest for Astrobiology: A Theoretical and Experimental Study

Savino Longo, Marcella D'Elia, Sergio Fonti, Francesca Mancarella, Gaia Micca Longo, Vincenzo Orofino

Abstract: Our collaboration recently focused on and proposed a class of mineral compositions which appear to be promising for organic matter delivery scenarios and past life detection. These mineral phases, which are provisionally named “white soft minerals” (WSMs), share a number of well-defined properties: chemical, physical, and “environmental” (like frequent association with water and/or past life forms). WSMs include Magnesite, Dolomite, Calcite, Mirabilite, Gypsum and many other phases. These minerals are being found with increasing frequency to be the key issue in several topics of astrobiological relevance, like organic matter delivery, Mars meteorites, Mars surface, minor bodies’ surface, detection of past life. In order to improve the present knowledge of the properties of such materials specially in the context of organic matter delivery we use several tools, like kinetic models for chemical decomposition, spectroscopy and gravimetric analysis. In this way we can assess promising features of WSMs like: (1) the considerable thermal mitigation which is provided by chemical decomposition, much more than by thermal radiation in a critical temperature range for organic survival; (2) the possibility to use the degree of chemical conversion to higher enthalpy phases as a “litmus paper” to evaluate a theoretical entry scenario; (3) the possibility to distinguish, by means of spectroscopic methods, biotic phases from abiotic, in particular for CaCO3. At the same time, differences between model results and gravimetry for CaCO3 suggest that available models need improvements like the consideration of gas diffusion in the materials. Future perspectives are discussed with indication of the more promising theoretical and experimental methods.

Planned Paper 5

Title: Out of equilibrium dynamics of water nanodroplets upon irradiation

  1. Feketeová1,*, T. Salbaing1, F. Berthias1, P. Bertier1, H. Abdoul-Carime1, F. Calvo2, B. Farizon1, M. Farizon1 and T. D. Märk3
  2. Université de Lyon; Université Claude Bernard Lyon1; Institut de Physique Nucléaire de Lyon, CNRS/IN2P3 UMR 5822, 69622 Villeurbanne Cedex, France.
  3. Université Grenoble 1, CNRS, LIPhy UMR 5588, F-38041 Grenoble, France.
  4. Institut für Ionenphysik und Angewandte Physik, Leopold Franzens Universität, 6020 Innsbruck, Austria.

Abstract: Water is abundant in molecular clouds and planetary systems, e.g., Kuiper Belt objects, satellites in solar system, such as, Europa, comets, and planetary rings. As we know the liquid water is necessary for all known life on Earth, thus, the potentially habitable planets are searched in the region around a star, where water can stay liquid on its surface and is assumed to form part of the planet’s atmosphere. The water in any of these objects is subjected to variety of radiation, e.g., cosmic ray particles, UV photons, or solar wind. The processing of water by energetic particles and photons plays an important role in astrochemistry and in the chemical evolution of the solar system. However, the nano-scale description of energy redistribution in out of equilibrium molecular systems upon the incident radiation is particularly challenging in this context.

In the experiments carried out with the device DIAM IPN Lyon, the relaxation of protonated water nanodroplets is observed after electronic excitation of one of its molecules. The implementation of a velocity map-imaging (VMI) method associated with the COINTOF technique (Correlated Ion and Neutral Time-Of-Flight) allowed us the measurement of the velocity distribution of molecules evaporated from protonated water clusters, mass- and energy preselected. The behavior of the measured velocity distributions shows that even for extremely small water nanodroplets, the complete energy redistribution before the evaporation prevails and the velocity distributions of these events is closed to those expected for macroscopic droplets from around ten water molecules. However, these measurements of the velocity distributions also highlight a high-speed distinct contribution corresponding to the evaporation of a molecule before complete redistribution of energy.

Planned Paper 6

Title: Water in the high-subcritical state as a trigger for the formation of ferric minerals and molecules of life, in the process of geobiotropy

Marie-Paule Bassez

Institut de Technologie, Université de Strasbourg, France

Abstract: Water in the high-subcritical, hsc, state shows properties which induce the synthesis of components of life concomitant to the transformation of rocks which contain ferrous silicates. It is shown that four chemical processes which occur at the T&P conditions of hsc water lead to the formation of prebiotic matter when N2/NH3 is present and of ferric oxide and silicate minerals: 1. Contact of hsc with ferrous silicate containing rocks; 2. High dissolution of silica in hsc; 3. Oxidation of FeII into FeIII in hsc and reduction of hsc to form H2; 4. Formation from CO2 of CO in hsc.

When crustal rising anoxic water encounters ferrous silicate containing rocks, while at 300°-350°C, 10-25 MPa, dissolution of the rocks can occur. Indeed, the solubility of silica is high below the critical point of water and drops abruptly above this point. The chemical equation for the anoxic alkaline oxidation of ferrous iron in hsc can be applied to the hydrolyses of fayalite, Fe2SiO4 and ferrosilite, FeSiO3, as I propose since 2013. FeIII-oxides and FeIII-silicates can form and H2 is released. H2 reacts with CO2 also in hsc water to form CO. Components of life can form at ~350°C such as macromolecules of amino acids which are experimentally synthesized from gaseous mixtures of (CO, N2, H2O) in Sabatier-Senderens/Fischer-Tropsch & Haber-Bosch reactions or in microwave or gamma-ray excitation reactions.

The possibility of such geobiotropic synthesis is demonstrated in a recent article (Bassez 2018) where it is developed for the Banded Iron Formations. It is developed here for the case of hydrothermal rocks observed on Earth and extraterrestrial objects.

Planned Paper 7

Title: Electrokinetics water extraction from arid areas and permafrost soils: the case of Mars

Hector-Andreas Stavrakakis and Elias Chatzitheodoridis

Abstract: Mars as planet is inside the habitability zone of the Sun and therefore it might still be hostile for earthlike life in a local scale after human intervention. Conditions that must be changed are the atmosphere which is lacking and shielding of the planetary surface from radiation is minimum, as well as the lack of water at the surface of the planet which has to be recovered. Despite the current situation of the planet, Mars was once a planet that could have sustained life. For the above reasons, Mars is a planet that in the last few decades is under scrutiny through a large fleet of orbiters and lander vehicles, with the intention to be once colonised.

It is generally accepted that water is the most essential ingredient for the existence of life. Water, also, plays a significant role in secondary processes and reactions that alter the regolith and form soil, making favourable environments for life to exist on the planet making its detection important for astrobiology [1]. Therefore, the detection of water-rich areas has been a very significant part of the Mars exploration programmes, and as such the above fleet has carried instruments with that in mind. These missions utilized optical imaging as well as measurements of physical properties in association with geophysics to find the water masses on Mars. The results have proven that water exists on Mars as ice caps of the poles, in fluid form in lakes below the ice caps, as permafrost in transient liquid brines in the upper layer of the Martian soil, and as the debatable flow of water on the slopes due to seasonality  [2], [3], [4].

Focusing primarily on future space missions or human utilization, and hence possibly colonisation of the planet, the control on water acquisition on Mars seems essential. Currently many methods have been proposed on how to acquire the water stored on Mars [5]. A scientific and technological discipline that seems to have a lot of potential is electro-kinetics as its approaches water in the molecular level.  With electro-kinetics an electrical field is applied that mobilises the ions in the soil inducing a hydraulic flow, which then concentrates the water in liquid pockets. The quality of the extracted water can be appropriate for human consumption and utilization [6]. These are the benefits of the application on heterogeneous fluids (fluids with microparticles), or on porous media, such as soils. Other benefits of the application of electrokinetics on soils include: (a) the stabilization of soils by moving the contained water and possibility of altering the soil chemistry and forming new minerals, and (b) the simultaneous electrolysis, which provides hydrogen and oxygen gases that are essential as space fuel or for human respiration.

Planned Paper 8

Title: Future Observatories of Planetary Evolution and Life on Habitable Planets

Shawn Domagal-Goldman

Abstract: Exoplanet science stands at a pivot point. The history of this field’s observations have focused on the detection of exoplanets and measurement of their orbital and bulk properties. The future of this field will focus on the characterization of exoplanets, driven by measurements of their chemical compositions. Eventually, this characterization will include planets that have size and orbital properties that allow for global surface water oceans, and therefore the potential for robust, global biospheres detectable across interstellar space. Here, we discuss the various mission concepts that aim to make these observations. We also discuss the main technical challenges in designing, building, and operating those missions. Finally, we discuss the potential science return from those missions, including the impact they will have on our understanding of “Planetary Evolution and the Search for Life on Habitable Planets.”

Planned Paper 9

Title: Culturable edaphic bacterial communities from the astrobiological analog site - the Mojave Desert.

Andrey A. Belov 1,* Vladimir S. Cheptsov 1,2 and Elena A. Vorobyova 1,2

1 Soil Science Faculty, Lomonosov Moscow State University, Moscow, Russia

2 Space Research Institute, Russian Academy of Sciences, Moscow, Russia

Abstract: Extreme arid Mojave Desert is one of the most considerable terrestrial analog objects for the astrobiological research due to its genesis, mineralogy, and climate. However, culturable bacterial communities from the Mojave Desert soils are poorly studied. We characterised soil aerobic heterotrophic bacterial communities from central region of the Mojave Desert. High total number of prokaryotic cells in situ and high proportion of cultivated forms were observed. Prevalence of Actinobacteria, ProteobacteriaFirmicutes and Bacteroidetes was found, whereas Actinobacteria was the most abundant phyla (more than 70% of isolates). The dominance of pigmented strains in culturable communities and high proportion of thermotolerant and pH-tolerant bacteria were detected. High tolerance to magnesium sulphate, moderate tolerance to sodium or potassium chlorides and magnesium perchlorate and vulnerability to sodium hydrocarbonate were detected. Low resistance to antibiotics was also revealed. Based on data obtained we conclude that bacterial communities of the Mojave Desert soil are well-adapted to different stress-factors including those, which are characterise in Martian regolith.

Planned Paper 10

Title: To be decided

Frances Westall

Planned Paper 11

Title: To be decided

Lena Noack et al.

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