52nd Lunar and Planetary Science Conference 2021 (LPI Contrib. No. 2548) 2291.pdf

HABITABILITY MODELS FOR PLANETARY SCIENCES. A. Méndez1, E. G. Rivera-Valentín2, D. Schulze- Makuch3, J. Filiberto2, R. Ramírez4, T. E. Wood5, A. Dávila6, C. McKay6, K. Ortiz-Ceballos1, M. Jusino-Maldonado1, N. J. Torres-Santiago1, G. Nery1, R. Heller7, P. Byrne8, M. J. Malaska9, E. Nathan10, M. F. Simões11, A. Antunes11, J. Martínez-Frías12, L. Carone13, N. R. Izenberg14, D. Atri15, H. I. Carvajal Chitty16, P. Nowajewski-Barra17, F. Rivera- Hernández18, C. Brown19, K. Lynch2, D. Catling20, J. I. Zuluaga21, J. F. Salazar22, H. Chen23, G. González5, J. M. Kashyap24, J. Haqq-Misra25, 1Planetary Habitability Laboratory, UPR Arecibo, USA ([email protected]), 2Lunar and Planetary Institute, USRA, USA, 3Technical University Berlin, Germany, 4Earth-Life Science Institute, Japan, 5International Institute of Tropical Forestry, USDA Forest Service, Puerto Rico, USA, 6NASA Ames Research Center, USA, 7Max Planck Institute for Solar System Research, Germany, 8North Carolina State University, USA, 9Jet Propulsion Laboratory / California Institute of Technology, USA, 10Brown University, USA, 11State Key Laboratory of Lunar and Planetary Sciences, China, 12Instituto de Geociencias (CSIC-UCM), Spain, 13Max Planck Institute for Astronomy, Germany, 14Johns Hopkins Applied Physics Laboratory, USA, 15Center for Space Science, New York University Abu Dhabi, United Arab Emirates, 16Universidad Simón Bolívar, Venezuela, 17Fundación Ciencias Planetarias, Chile, 18School of Earth and Atmospheric Sciences, Georgia Tech, USA, 19Macquarie University, Australia, 20University of Washington, USA, 21Institute of Physics / FCEN - Universidad de Antioquia, Colombia, 22GIGA, Escuela Ambiental, Facultad de Ingeniería, Universidad de Antioquia, Colombia, 23Northwestern University, USA, 24Jyoti Nivas College, Bengaluru, India, 25Blue Marble Space Institute of Science, USA.

Introduction: One of the problems in astrobiology is through the use of HSMs, their results can be mapped to how to define and measure the habitability not only of the same standard scale (e.g., zero for worst and one for terrestrial environments but also of planetary best regions). A Habitability Readiness Analysis (HRA) environments, from the Solar System to extrasolar of any mission could be used to determine how its planets [1]. The word habitability literally means the existing instruments could be used, or what sensors quality of habitat (the suffix -ity means quality, state, or should be added, for measurements in the spatial and condition). Astrobiologists have been constructing temporal habitability scales of interest. Furthermore, it different general definitions of habitability, not might also be possible to develop new sensors for direct necessarily consistent with one another, for some time habitability measurements. [e.g., 2,3,4,5,6,7]. Other more specific habitability Recommendations for Planetary Missions: Planetary definitions, such as the canonical Habitable Zone (i.e., exploration missions are playing a critical role in our presence of surface liquid water on Earth-like planets), understanding of planetary habitability beyond what are used in exoplanet science [8]. Ecologists have been remote sensing from space can provide. Planetary using since the 1980s the Habitat Suitability Models exploration mission designs for the upcoming decades (HSMs) to study the habitability of Earth from local to may have major astrobiological components that can global scales; however, this is seldom utilized in the directly or indirectly inform the study of habitability in astrobiology community [9]. the Solar System — even if the determination of Here we recommend adapting and expanding the habitability is not the primary focus of a mission. ecologists’ nearly four decades of experience modeling Indeed, general mission components not directly habitability on Earth to astrobiology and planetary designed for astrobiological purposes might usefully studies. These models can be used to characterize the contribute to habitability studies with only minimal spatial and temporal distribution of habitable considerations in design. Here we list four main environments, identify regions of interest in the search recommendations for the planetary community: for life, and, eventually, explore correlations between 1. Increase and widen the participation of more habitability and biosignatures. For example, such experts on habitat suitability models. Ecologists are models would help to test the hypothesis that the experts in the ground-truthed proven measurement biosignatures (or biomarkers) are positively correlated of terrestrial habitability, yet they are seldom with proxy indicators of geologically habitable represented in the planetary and astrobiology environments (or geomarkers); i.e., there is life community. New synergies between NASA and the whenever there are habitable environments on Earth. national and international ecological societies, e.g., the Measurements by past and future planetary missions Ecological Society of America (ESA), Soil Ecology can be combined into a standard library of habitability Society (SES), and the International Society for models. Results from different missions can then be Microbial Ecology (ISME), should be established via, compared, even using different measurements, since, for example, a joint conference session at the Lunar and 52nd Lunar and Planetary Science Conference 2021 (LPI Contrib. No. 2548) 2291.pdf

Planetary Science Conference. There should be future missions could be compared to each other and worldwide participation to guarantee global their habitability assessments refined, and new standardization. This synergy will stimulate the habitability knowledge gaps could be identified. This participation and exploration of the Solar System as a dynamic standard should be evaluated and updated laboratory for expanding our current understanding of regularly by a diverse and multidisciplinary committee, the habitability of Earth. for example during a Decadal Survey and/or mid- decade review. Currently, the closest concept to an NHS 2. Further terrestrial exploration. Many Earth is specific language included in various NASA habitats are vastly under-explored biologically. For roadmaps, such as the NASA Astrobiology Roadmap example, the clouds, stratosphere, deep ocean, deep ice, [10] and the NASA Roadmap to Ocean Worlds [11]. deep earth, or the mantle. Further, astrobiology needs to These documents stress the need for habitability make stronger connections to the researchers working in evaluations and missions (e.g., Europa Clipper and these under-studied environments (e.g., The Deep Titan Dragonfly), yet only focus on the individual Carbon Observatory) so that there is a cohesive habitability requirements and not how to combine the understanding of the state-of-the-art science being net contribution of these factors. Furthermore, the NHS learned and efforts to continue to study these might eventually become the standard of other environments are supported. These field studies should disciplines. provide new data to test the applicability of current habitability models with extreme environments, and Conclusion: NASA should create habitability standards thus get us closer to diverse planetary conditions. At the for planetary missions with astrobiology objectives, as same time, unicellular life continually surprises us with the U.S. Fish and Wildlife Service successfully did long new ways to survive and obtain energy from its ago for ecologists. These standards are necessary to environment (rock-eaters, electric currents, and even make sense of data from multiple missions, develop radioactivity) which shows us we need to be flexible in predictions for environmental niches on planetary considering energy sources for habitability. bodies that can be tested, and understand the extraterrestrial correlations between habitability and 3. Improve habitability models. New habitability biosignatures. There is no need for the planetary and models should be developed and validated with field astrobiology community to reinvent the habitability and laboratory experiments, including simulated methods and tools used by ecologists. The synergy extreme and planetary analog environments. The main between the methods used by ecologists and goal is to identify knowledge gaps. For example, new astrobiologists will help to integrate and expand our ecophysiological response curves (e.g., growth rate as a understanding of the habitability of Earth, the Solar function of water activity, a measure of available water) System, and extrasolar planets. for some organisms are necessary, especially in dynamic environments such as gradient-rich biotopes Acknowledgments: This work was supported by the and higher complexity extreme environments (i.e., those NASA Astrobiology Institute (NAI), the Planetary with multiple extremes such as deep-sea brines). Also, Habitability Laboratory (PHL), and the University of there are insufficient models on microbial growth in Puerto Rico at Arecibo (UPR Arecibo). near-surface dynamic environments (e.g., as applicable References: [1] Méndez, A., et al. (2020), arXiv e- to martian diurnal cycles). There is a growing body of prints, arXiv:2007.05491. [2] Shock, E. L., & Holland, literature about the manifold mechanisms through M. E. (2007), Astrobiology, 7, 839. [3] Hoehler, T. M. which life affects the Earth’s climate system, including (2007), Astrobiology, 7, 824. [4] Cardenas, R., Perez, the global energy balance and atmospheric composition N., Martinez-Frias, J., & Martin, O. (2014), Challenges, and dynamics. Advances in the understanding of 5, 284. [5] Cockell, C. S., et al. (2016), Astrobiology, climate-life interactions in the Earth System can provide 16, 89. [6] Cárdenas, R., Nodarse-Zulueta, R., Perez, N., new insights for habitability models. Avila-Alonso, D., & Martin, O. (2019), 2nd 4. Develop a NASA Habitability Standard (NHS). International Conference on BioGeoSciences, 1. [7] Existing and future planetary missions should specify Heller, R. (2020), Nature Astronomy, 4, 294. [8] how they assess habitability for each of their Kasting, J. F., Whitmire, D. P., & Reynolds, R. T. instruments according to a shared NASA habitability (1993), Icarus, 101, 108. [9] USFWS (1980), standard. For example, measurements of surface Ecological Services Manual. [10] Des Marais, D. J., et temperature and water vapor from landers or orbital al. (2003), Astrobiology, 3, 219. [11] Hendrix, A. R., et missions could be converted into a simple habitability al. (2019), Astrobiology, 19, 1. model. The advantage of a standard is that past and