Extremophiles: a special or general case in the search for extra-terrestrial life?

TL;DR

This paper examines whether extremophiles are a special or general case in the search for extraterrestrial life, considering their adaptability, origins, and implications for habitable worlds beyond Earth.

Contribution

It introduces a theoretical framework to evaluate extremophiles' role in astrobiology and questions the assumption that extremophiles are indicative of extraterrestrial life.

Findings

Extremophiles may not represent the earliest or most common form of life.

Earth's habitability might be an extreme or average case, affecting search strategies.

The search for extraterrestrial life should consider the broader context of planetary habitability.

Abstract

Since time immemorial life has been viewed as being fragile, yet over the past few decades it has been found that many extreme environments are inhabited by organisms known as extremophiles.Knowledge of their emergence, adaptability, and limitations seems to provide a guideline for the search of extra-terrestrial life, since some extremophiles presumably can survive in extreme environments such as Mars, Europa, and Enceladus. Due to physicochemical constraints, the first life necessarily came into existence at the lower limit of lifes conceivable complexity.Thus, the first life could not have been an extremophile, furthermore, since biological evolution occurs over time, then the dual knowledge regarding what specific extremophiles are capable of, and to the analogue environment on extreme worlds, will not be sufficient as a search criterion.This is because, even though an extremophile can live in an extreme environment here-and-now, its ancestor however could not live in that very same environment in the past, which means that no contemporary extremophiles exist in that environment.Furthermore, a theoretical framework should be able to predict whether extremophiles can be considered a special or general case in the galaxy.Thus, a question is raised: does Earths continuous inhabitability represent an extreme or average value for planets? Thus, dependent on whether it is difficult or easy for worlds to maintain this inhabitability, the search for extra-terrestrial life with a focus on extremophiles will either represent a search after dying worlds, or a search after special life on living worlds, where one focus too narrowly on extreme values.