| 1. |
- Konatham, Samuel, et al.
(author)
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Atmospheric composition of exoplanets based on the thermal escape of gases and implications for habitability
- 2020
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In: Proceedings of the Royal Society. Mathematical, Physical and Engineering Sciences. - : Royal Society. - 1364-5021 .- 1471-2946. ; 476:2241
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Journal article (peer-reviewed)abstract
- The detection of habitable exoplanets is an exciting scientific and technical challenge. Owing to the current and most likely long-lasting impossibility of performing in situ exploration of exoplanets, their study and hypotheses regarding their capability to host life will be based on the restricted low-resolution spatial and spectral information of their atmospheres. On the other hand, with the advent of the upcoming exoplanet survey missions and technological improvements, there is a need for preliminary discrimination that can prioritize potential candidates within the fast-growing list of exoplanets. Here we estimate, for the first time and using the kinetic theory of gases, a list of the possible atmospheric species that can be retained in the atmospheres of the known exoplanets. We conclude that, based on our current knowledge of the detected exoplanets, 45 of them are good candidates for habitability studies. These exoplanets could have Earth-like atmospheres and should be able to maintain stable liquid water. Our results suggest that the current definition of a habitable zone around a star should be revisited and that the capacity of the planet to host an Earth-like atmosphere to support the stability of liquid water should be added.
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| 2. |
- Konatham, Samuel, 1992-
(author)
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Atmospheric Species and Spectral Radiation in Terrestrial Exoplanets : Implications for Astrobiology
- 2022
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Doctoral thesis (other academic/artistic)abstract
- The physical properties of the planets and their parent stars are fundamental in the composition of atmospheres and radiative environments, which fundamentally determine their surface temperature and habitability. The atmospheric composition and radiation play a vital role in the emergence of life. This doctoral thesis presents two main results: 1. A method that uses the physical properties of the planets and their parent stars to infer the potential atmospheric compositions of the known exoplanets. For that, fundamental physics concepts and the basics of the kinetic theory of gases are used. Additionally, a new list of potentially habitable exoplanets is presented based on the resulting atmospheric compositions and the criteria that Earth-like atmospheres that can host liquid water should be considered habitable. The presented method also provides a preliminary classification of exoplanets similar to Earth (in terms of atmosphere) and their potential habitability. 2. A study of the impact of the radiation environment on the development and evolution of the human visual system towards optimal use of the available radiation. Human vision's possible evolutionary directions are presented while overcoming the shortcomings in the existing studies. The human visual system is hypothesised to have evolved in conjugation with the prevailing spectral radiation environment for photopic (daytime) and scotopic (night-time). One of the main novelties of this study is the comparison of the human vision bandwidth with the Full Width at half-maximum (FWHM) of the radiation reaching the shallow depths of the ocean, which may suggest that this is optimized for the development of animal sight during the formation of the early proto-visual system. Moreover, the observed maximum absorption wavelength during photopic vision (555nm) correlates with the maximum total energy for a 300 nm vision bandwidth. Furthermore, the analysis of the radiation environment at different solar zenith angles (SZA) during dusk suggests that the scotopic vision evolved to optimize information retrieval during these hours. The work presented in this thesis contributes to perform screening of Earth-like exoplanets and the study of astrobiological or space exploration aspects such as potential habitability, human-like vision, photosynthesis efficiency and evolution of life systems on exoplanets.
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| 3. |
- Konatham, Samuel, et al.
(author)
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The Impact of the Spectral Radiation Environment on the Maximum Absorption Wavelengths of Human Vision and Other Species
- 2021
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In: Life. - : MDPI. - 2075-1729. ; 11:12
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Journal article (peer-reviewed)abstract
- Since the earliest development of the eye (and vision) around 530 million years ago (Mya), it has evolved, adapting to different habitats, species, and changing environmental conditions on Earth. We argue that a radiation environment determined by the atmosphere played a determining role in the evolution of vision, specifically on the human eye, which has three vision regimes (photopic-, scotopic-, and mesopic vision) for different illumination conditions. An analysis of the irradiance spectra, reaching the shallow ocean depths, revealed that the available radiation could have determined the bandwidth of the precursor to vision systems, including human vision. We used the radiative transfer model to test the existing hypotheses on human vision. We argue that, once on the surface, the human photopic (daytime) and scotopic (night-time) vision followed different evolutionary directions, maximum total energy, and optimum information, respectively. Our analysis also suggests that solar radiation reflected from the moon had little or no influence on the evolution of scotopic vision. Our results indicate that, apart from human vision, the vision of only a few birds, rodents, and deep-sea fish are strongly correlated to the available radiation within their respective habitats.
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| 4. |
- Martin-Torres, Javier, et al.
(author)
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The HABIT (HabitAbility: Brine Irradiation and Temperature) environmental instrument for the ExoMars 2022 Surface Platform
- 2020
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In: Planetary and Space Science. - : Elsevier. - 0032-0633 .- 1873-5088. ; 190
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Journal article (peer-reviewed)abstract
- The HABIT (HabitAbility: Brine Irradiation and Temperature) instrument is a European payload of the ExoMars 2022 Surface Platform Kazachok that will characterize the present-day habitability at its landing place in Oxia Planum, Mars. HABIT consists of two modules: (i) EnvPack (Environmental Package) that monitors the thermal environment (air and ground), the incident ultraviolet radiation, the near surface winds and the atmospheric dust cycle; and (ii) BOTTLE (Brine Observation Transition To Liquid Experiment), an In-situ Resource Utilization instrument to produce liquid water for future Mars exploration. BOTTLE will be used also to investigate the electrical conductivity properties of the martian atmosphere, the present-day atmospheric-ground water cycle and to evaluate if liquid water can exist on Mars in the form of brines, and for how long. These variables measured by HABIT are critical to determine the present and future habitability of the martian surface. In this paper, we describe in detail the HABIT instrument and sensors, together with the calibration of its Flight Model (FM) and the Engineering Qualification Model (EQM) versions. The EnvPack module has heritage from previous missions operating on the surface of Mars, and the environmental observations of its sensors will be directly comparable to those delivered by those missions. HABIT can provide information of the local temperature with ±0.2 °C accuracy, local winds with ±0.3 m/s, surface brightness temperature with ±0.8 °C, incident UV irradiance with 10% error of its absolute value in the UV-A, UV-B, UV-C ranges, as well as in the total UV-ABC range, and two additional wavebands, dedicated to ozone absorption. The UV observations can be used to derive the total opacity column and thus monitor the dust and ozone cycles. BOTTLE can demonstrate the hydration state of a set of four deliquescent salts, which have been found on Mars (calcium chloride, ferric sulphate, magnesium perchlorate and sodium perchlorate) by monitoring their electric conductivity (EC). The EC of the air and the dry salts under Earth ambient, clean room conditions is of the order of 0.1 μScm−1. We have simulated HABIT operations, within an environmental chamber, under martian conditions similar to those expected at Oxia Planum. For dry, CO2 atmospheric conditions at martian pressures, the air EC can be as low as 10−8 μScm−1, however it increases with the relative humidity (RH) percentage. The laboratory experiments show that after an increase from 0 to 60% RH within a few hours, the EC of the air increased up to 10−1 μScm−1, magnesium perchlorate hydrated and reached values of 10 μScm-1, whereas calcium chloride deliquesced forming a liquid state with EC of 102 μScm−1. HABIT will operate with a regular cadence, through day and night. The Electronic Unit (EU) is protected with a heater that is activated when its temperature is below −33 °C and disabled if the temperature of the surface platform rises above −30 °C. Additionally, the heaters of the BOTTLE unit can be activated to dehydrate the salts and reset the experiment. HABIT weighs only 918 g. Its power consumption depends on the operation mode and internal temperature, and it varies between 0.7 W, for nominal operation, and 13.1 W (when heaters are turned on at full intensity). HABIT has a baseline data rate of 1.5 MB/sol. In addition to providing critical environmental observations, this light and robust instrument, will be the first demonstrator of a water capturing system on the surface of Mars, and the first European In-Situ Resource Utilization in the surface of another planet.
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