A limbus mundi elucidation of habitability: the Goldilocks Edge

TL;DR

This paper proposes shifting focus from the traditional habitable zone to a specific spatial and temporal 'Goldilocks Edge' on planets, where conditions for life emergence are more precisely defined by localized interactions of key elements and energy sources.

Contribution

It introduces the concept of the Goldilocks Edge, emphasizing localized regions and times on planets where conditions favor the emergence of life, beyond the traditional habitable zone concept.

Findings

Identifies the importance of spatial and temporal windows for habitability.

Highlights the role of interactions between solvents, elements, and energy sources.

Suggests the concept of a prebiotic spot as a key factor for life's emergence.

Abstract

The habitable zone is the circumstellar region in which a terrestrial-mass planet with an atmosphere can sustain liquid water on its surface. However, despite the usefulness of this concept, it is being found to be increasingly limiting in a number of ways. The following is known: (i) Liquid water can exist on worlds for reasons unrelated to its specific distance from a star. (ii) Energy sources can exist for reasons unrelated to the distance to a star. Furthermore, the habitable zone is based on both astronomy: the distance and stellar energy, and chemistry: liquid water and the right temperature. However, these factors are only part of the consideration. Thus, discussions of habitability and the possibility for the emergence of life on a world must consider the evolutionary principles that govern life as well as the laws that govern stellar and planetary science. This is important because the following is also known: (iii) The time window for the emergence of life is within 600 million years. (iv) The Earth was an extreme environment overall in the period when this window existed. (v) The first life was necessarily fragile. Therefore, chemical evolution must have taken place in a relatively protected and restricted environment. Thus, rather than as in the Goldilocks zone, which focuses too narrowly on the world as a whole, this paper suggests that it is better to focus on a particular region and time period on a world, in which fitting conditions for habitability exist. Thus, the following is suggested: The Goldilocks Edge is a spatial and temporal window on an astronomical body or planemo, where liquid solvents, SPONCH elements, and energy sources exist. Furthermore, since the mere presence of these do not in themselves necessarily lead to the emergence of life, this possibility only arises when these interact. Thus, the prebiotic spot will be suggested.