Detection of biosignatures in terrestrial Mars analogs: Strategical and technical assessments

Abstract

The search for potential signs of Martian life has been planned and implemented by worldwide countries for decades. Due to the high expenditure on Mars exploration, more easily accessible Marslike regions on Earth are invaluable targets for astrobiology research to understand the detection of potential Martian biosignatures. In order to detect potential life signals beyond Earth, questions on how to define life and biosignatures need to be carefully inspected. This review summarizes scientific instrumental techniques, our "eyes" and "hands", that facilitate identifying and quantifying biosignatures on Mars. Scientific devices that can be applied in astrobiology include electromagnetic spectrum-based spectrometers, mass spectrometers, redox potential indicators, circular dichroism polarimeters, in situ nucleic acid sequencers, life isolation/cultivation systems, and imagers. These techniques should be first tested in Mars analog extreme environments on Earth to validate their practicality on Mars. To better understand the instrumental detectability of biosignatures on Mars through its evolutionary history, terrestrial Mars analogs are divided into four major categories according to their similarities to different geological ages of Mars (the Early-Middle Noachian Period, the Late Noachian-Early Hesperian Period, the Late Hesperian-Early Amazonian Period, and the Middle-Late Amazonian Period). Future missions are suggested to explore more on the early terrains in Mars' Southern Hemisphere once the landing issue is solved engineeringly, since these explorations permit investigating a continuum of the habitability shift through Mars geological history. Moreover, practical applications of scientific instruments listed above are briefly reviewed based on the four categories of Mars analogs, and instruments applied for autonomous robotic rover tests in Mars analogs are further discussed. For engineering efficiency, a Mars rover ought to be equipped with as few assemblable instruments as possible. Therefore, once candidate landing regions 1 Biosignatures in Mars analogson Mars are defined, the portable suites of instruments should be smartly devised on the basis of the geological, geochemical, geomorphological, and chronological characteristics of the landing regions. Laboratory-based experiments without engineering restrictions are further encouraging and appealing if Mars sample-return missions are successfully completed. To exclude false positive and false negative conclusions in life discovery, the combined use and replication studies of multiple analytical techniques must be performed to confirm the observational results.

Brine Pools With Round Caps in the Western Qaidam Basin: Application to Iron Mobility and the Evaporation Formation of the Iron Oxide and Sulfate Assemblage on Mars

“…The age of the Meridiani deposits is uncertain but probably dates to the late Noachian/early Hesperian (Arvidson et al, 2003;Hynek & Di Achille, 2017;Squyres & Knoll, 2005). The western Qaidam Basin is thought to be analogous to environments on Mars during the late Noachian to early Hesperian (Shen et al, 2022), so the origins of the Meridiani deposits and sediments in this study may be similar.…”

Geochemical and Biological Profiles of a Quartz Stone in the Qaidam Mars Analog Using LIBS: Implications for the Search for Biosignatures on Mars

“…The western Qaidam Basin is an exemplary Mars analog in accordance with its low water activity and the resultant landforms, including gravel deposition, pits, dunes, troughs, and aeolian ridges. ,,− ,− In Mars-like environments, hypolithic communities are usually acknowledged as a high-priority target for biosignature detection. ,,, This study is one of the pioneering spectroscopic Qaidam investigations that combine LIBS and Raman instrumentations to survey the biotic signal of possible hypolithic communities from chemical and mineralogical profiles. ,, …”

“…The significance of a LIBS application to astrobiology has been surveyed in several Mars analog environments. ,− Data generated by LIBS are generally coupled to multivariate statistical techniques; ordination techniques like PCA and linear discriminant analysis (LDA) can be used to discriminate different sources, even different bacterial species and dead/alive cells, based on LIBS spectra. ,, Since multivariate analyses take all measured points into account, these techniques are possible to retrieve trivial differences caused by special spatial distribution patterns of elements and their physical/emission interactions in the laser-generated electrically conducting mediumplasma. Among multivariate analysis techniques, discriminant analysis LDA and PLS-DA as supervised or semi-supervised methods separate groups selectively based on preassigned different experimental units, − while PCA is an unsupervised method that generates the optimal differentiating components without foreknowledge about experimental units .…”

A Simple Biochemical Method for the Detection of Proteins as Biomarkers of Life on Martian Soil Simulants and the Impact of UV Radiation

“…Planetary exploration focuses on the search for traces of life as signatures to investigate habitability on other planets. Macromolecules, such as lipids [ 1 ], nucleic acids [ 2 ], and proteins and amino acids [ 3 ], could be considered as life signatures for exploring the existence of life on other planets. Even though extra-terrestrial life may not be similar in chemical structure to life on Earth, it is still essential to use macromolecules which are based on life as we know as references for searching potential biosignatures on soils from other planets.…”