A Proposed Geobiology-Driven Nomenclature for AstrobiologicalIn SituObservations and Sample Analyses

Abstract

As the exploration of Mars and other worlds for signs of life has increased, the need for a common nomenclature and consensus has become significantly important for proper identification of nonterrestrial/non-Earth biology, biogenic structures, and chemical processes generated from biological processes. The fact that Earth is our single data point for all life, diversity, and evolution means that there is an inherent bias toward life as we know it through our own planet's history. The search for life ''as we don't know it'' then brings this bias forward to decision-making regarding mission instruments and payloads. Understandably, this leads to several top-level scientific, theoretical, and philosophical questions regarding the definition of life and what it means for future life detection missions. How can we decide on how and where to detect known and unknown signs of life with a single biased data point? What features could act as universal biosignatures that support Darwinian evolution in the geological context of nonterrestrial time lines? The purpose of this article is to generate an improved nomenclature for terrestrial features that have mineral/microbial interactions within structures and to confirm which features can only exist from life (biotic), features that are modified by biological processes (biogenic), features that life does not affect (abiotic), and properties that can exist or not regardless of the presence of biology (abiogenic). These four categories are critical in understanding and deciphering future returned samples from Mars, signs of potential extinct/ancient and extant life on Mars, and in situ analyses from ocean worlds to distinguish and separate what physical structures and chemical patterns are due to life and which are not. Moreover, we discuss hypothetical detection and preservation environments for extant and extinct life, respectively. These proposed environments will take into account independent active and ancient in situ detection prospects by using previous planetary exploration studies and discuss the geobiological implications within an astrobiological context.

Observations of Elemental Composition of Enceladus Consistent with Generalized Models of Theoretical Ecosystems

“…First, we echo previous calls in the astrobiology literature to explore more generalized notions of metabolism and physiology [28, 42, 51]. Our analyses suggest that while assuming terrestrial allometry and ecosystem size-structure could yield theoretical non-negligible biomass and biological stoichiometries that are within the ranges of N:P ratios suggested by Cassini data, these cases are marginal.…”

Marine Science Can Contribute to the Search for Extra-Terrestrial Life

“…Extraterrestrial life has been contemplated as inhabiting energy-providing rocky-aqueous environments and being capable of carrying out metabolic functions that allow growth and movement [ 200 , 201 , 202 , 203 , 204 , 205 ], such as prokaryotic-like life forms (either Bacteria and Archea or protozoans) [ 124 , 206 ]. Also, models for encoding and transmitting information regarding structural character and metabolic activity are based on DNA or RNA, molecules with a series of basic elements arranged in different sequences.…”

Introduction—First Billion Years: Habitability

“…In this special collection, research and review articles resulting from the meeting are presented. Diverse topics are covered including revisiting what martian meteorite ALH 84001 constrains about the habitability of Early Mars (Treiman, 2021 , this issue), an investigation into Earth's oxygenation history using banded iron formations (Schulz, 2021 , this issue), and a new geobiology-driven nomenclature for astrobiological in situ observations and sample analyses (Perl et al , 2021 , this issue). In this report, we summarize the conference themes, the discussion at the workshop, and the questions still to be investigated about forming habitable planets and the potential emergence of life within our Solar System and beyond.…”