Similarity indexing of exoplanets in search for potential habitability: application to Mars-like worlds

Abstract

Study of exoplanets is one of the main goals of present research in planetary sciences and astrobiology. Analysis of huge planetary data from space missions such as CoRoT and Kepler is directed ultimately at finding a planet similar to Earth -- the Earth's twin, and answering the question of potential exo-habitability. The Earth Similarity Index (ESI) is a first step in this quest, ranging from 1 (Earth) to 0 (totally dissimilar to Earth). It was defined for the four physical parameters of a planet: radius, density, escape velocity and surface temperature. The ESI is further sub-divided into interior ESI (geometrical mean of radius and density) and surface ESI (geometrical mean of escape velocity and surface temperature). The challenge here is to determine which exoplanet parameter(s) is important in finding this similarity; how exactly the individual parameters entering the interior ESI and surface ESI are contributing to the global ESI. Since the surface temperature entering surface ESI is a non-observable quantity, it is difficult to determine its value. Using the known data for the Solar System objects, we established the calibration relation between surface and equilibrium temperatures to devise an effective way to estimate the value of the surface temperature of exoplanets for further analysis with our graphic methodology. A new approach, called Mars Similarity Index (MSI), is introduced to identify planets that may be habitable to the extreme forms of life. MSI is defined in the range between 1 (present Mars) and 0 (dissimilar to present Mars) and uses the same physical parameters as ESI. We are interested in Mars-like planets to search for planets that may host the extreme life forms, such as the ones living in extreme environments on Earth; for example, methane on Mars may be a product of the methane-specific extremophile life form metabolism.

14 pages

References in corpus (5)

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• The Climate of Early Mars
• The mass of the Mars-sized exoplanet Kepler-138 b from transit timing
• Connecting the dots III: Night side cooling and surface friction affect climates of tidally locked terrestrial planets
• Hypotheses for near-surface exchange of methane on Mars

Cited by in corpus (8)

• Habitability Models for Astrobiology
• Drift Rates of Narrowband Signals in Long-term SETI Observations for Exoplanets
• Advanced Aspects of the Galactic Habitability
• Earth-like and Tardigrade survey of exoplanets
• Quantifying the Classification of Exoplanets: in Search for the Right Habitability Metric
• A fuzzy Multi-Criteria Decision Making approach for Exo-Planetary Habitability
• Indexing Exoplanets with Physical Conditions Potentially Suitable for Rock-Dependent Extremophiles
• An Informational-Entropic Approach to Exoplanet Characterization