On the Habitability of Aquaplanets

Abstract

An Aquatic Habitability Index is proposed, based on Quantitative Habitability Theory, and considering a very general model for life. It is a primary habitability index, measuring habitability for phytoplankton in the first place. The index is applied to some case studies, such as the habitability changes in Earth due to environmental perturbations caused by asteroid impacts.

On the quantification of habitability: merging the astrobiological and ecological schools

“…In this work, we use the general formalism for devising habitability indexes described in Cardenas et al (2014;2017), which concludes that a primary aquatic habitability index for a photosynthetically dominated ecosystem in principle can be formulated as:…”

“…All these functions can be normalized to be in the range {0 − 1}. In Cardenas et al (2014;2017) two particular versions of this index were devised and applied. However, those versions were applied to oceanic and coastal environments.…”

“…In this work, we use the general formalism for devising habitability indexes described in Cardenas et al . (2014; 2017), which concludes that a primary aquatic habitability index for a photosynthetically dominated ecosystem in principle can be formulated as: where f ( L ), f ( N ) and f ( T ) are functions of light, nutrients and temperature, respectively. All these functions can be normalized to be in the range {0 − 1}.…”

“…However, Quantitative Habitability Theory (QHT), born inside the astrobiological community, is scalable in space and time. In this paper, we use tools of QHT to devise a new version of our Aquatic Primary Habitability (APH) index (Cardenas et al, 2014;Cardenas, 2017) to apply for the first time to freshwater ecosystems under perturbations of their optical quality. Then we embed the index in an ecological model of trophic levels, a phytoplankton-zooplankton dynamics which we modified from Ferrero et al (2006).…”

Habitability Models for Astrobiology

“…The word habitability literally means the quality of habitat (the suffix -ity denotes a quality, state, or condition). Astrobiologists have been constructing different general definitions of habitability, not necessarily consistent with one another (e.g., Shock & Holland, 2007;Hoehler, 2007;Cardenas et al, 2014;Cockell et al, 2016;Cárdenas et al, 2019;Heller, 2020). Other more specific habitability definitions, such as the canonical Habitable Zone (i.e., the orbital region in which liquid water could exist on the surface of a planet), are used in exoplanet science (Kasting et al, 1993).…”