An Alternative Approach for Assessing Biogenicity
Metadata
Show full item recordEditorial
Mary Ann Liebert
Date
2020-10Referencia bibliográfica
Rouillard, J., van Zuilen, M., Pisapia, C., & Garcia-Ruiz, J. M. (2020). An Alternative Approach for Assessing Biogenicity. Astrobiology. [DOI: 10.1089/ast.2020.2282]
Abstract
The search for signs of life in the ancient rock record, extreme terrestrial environments, and other planetary bodies
requires a well-established, universal, and unambiguous test of biogenicity. This is notably true for cellular remnants
of microbial life, since their relatively simple morphologies resemble various abiogenic microstructures that occur in
nature. Although lists of qualitative biogenicity criteria have been devised, debates regarding the biogenicity of many
ancient microfossils persist to this day. We propose here an alternative quantitative approach for assessing the
biogenicity of putative microfossils. In this theoretical approach, different hypotheses—involving biology or not and
depending on the geologic setting—are put forward to explain the observed objects. These hypotheses correspond to
specific types of microstructures/systems. Using test samples, the morphology and/or chemistry of these systems are
then characterized at the scale of populations. Morphologic parameters include, for example, circularity, aspect ratio,
and solidity, while chemical parameters could include elementary ratios (e.g., N/C ratio), isotopic enrichments (e.g.,
d13C), or chirality (e.g., molar proportion of stereoisomers), among others. Statistic trends distinguishing the different
systems are then searched for empirically. The trends found are translated into ‘‘decision spaces’’ where the different
systems are quantitatively discriminated and where the potential microfossil population can be located as a single
point. This approach, which is formulated here on a theoretical level, will solve several problems associated with the
classical qualitative criteria of biogenicity. Most importantly, it could be applied to reveal the existence of cellular life
on other planets, for which characteristics of morphology and chemical composition are difficult to predict. Key
Words: Biosignatures—Biogenicity—Astrobiology—Early life—Cellular life. Astrobiology 21, xxx–xxx.