Diverse organic-mineral associations in Jezero crater, Mars.

The presence and distribution of preserved organic matter on the surface of Mars can provide key information about the Martian carbon cycle and the potential of the planet to host life throughout its history. Several types of organic molecules have been previously detected in Martian meteorites1 and at Gale crater, Mars2-4. Evaluating the diversity and detectability of organic matter elsewhere on Mars is important for understanding the extent and diversity of Martian surface processes and the potential availability of carbon sources1,5,6. Here we report the detection of Raman and fluorescence spectra consistent with several species of aromatic organic molecules in the Máaz and Séítah formations within the Crater Floor sequences of Jezero crater, Mars. We report specific fluorescence-mineral associations consistent with many classes of organic molecules occurring in different spatial patterns within these compositionally distinct formations, potentially indicating different fates of carbon across environments. Our findings suggest there may be a diversity of aromatic molecules prevalent on the Martian surface, and these materials persist despite exposure to surface conditions. These potential organic molecules are largely found within minerals linked to aqueous processes, indicating that these processes may have had a key role in organic synthesis, transport or preservation.

In Situ Identification of Paleoarchean Biosignatures Using Colocated Perseverance Rover Analyses: Perspectives for In Situ Mars Science and Sample Return.

The NASA Mars 2020 Perseverance rover is currently exploring Jezero crater, a Noachian-Hesperian locality that once hosted a delta-lake system with high habitability and biosignature preservation potential. Perseverance conducts detailed appraisals of rock targets using a synergistic payload capable of geological characterization from kilometer to micron scales. The highest-resolution textural and chemical information will be provided by correlated WATSON (imaging), SHERLOC (deep-UV Raman and fluorescence spectroscopy), and PIXL (X-ray lithochemistry) analyses, enabling the distributions of organic and mineral phases within rock targets to be comprehensively established. Herein, we analyze Paleoarchean microbial mats from the ∼3.42 Ga Buck Reef Chert (Barberton greenstone belt, South Africa)-considered astrobiological analogues for a putative ancient martian biosphere-following a WATSON-SHERLOC-PIXL protocol identical to that conducted by Perseverance on Mars during all sampling activities. Correlating deep-UV Raman and fluorescence spectroscopic mapping with X-ray elemental mapping, we show that the Perseverance payload has the capability to detect thermally and texturally mature organic materials of biogenic origin and can highlight organic-mineral interrelationships and elemental colocation at fine spatial scales. We also show that the Perseverance protocol obtains very similar results to high-performance laboratory imaging, Raman spectroscopy, and µXRF instruments. This is encouraging for the prospect of detecting microscale organic-bearing textural biosignatures on Mars using the correlative micro-analytical approach enabled by WATSON, SHERLOC, and PIXL; indeed, laminated, organic-bearing samples such as those studied herein are considered plausible analogues of biosignatures from a potential Noachian-Hesperian biosphere. Were similar materials discovered at Jezero crater, they would offer opportunities to reconstruct aspects of the early martian carbon cycle and search for potential fossilized traces of life in ancient paleoenvironments. Such samples should be prioritized for caching and eventual return to Earth.

Raman Characterization of the CanMars Rover Field Campaign Samples Using the Raman Laser Spectrometer ExoMars Simulator: Implications for Mars and Planetary Exploration.

The Mars 2020 Perseverance rover landed on February 18, 2021, and has started ground operations. The ExoMars Rosalind Franklin rover will touch down on June 10, 2023. Perseverance will be the first-ever Mars sample caching mission-a first step in sample return to Earth. SuperCam and Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals (SHERLOC) on Perseverance, and Raman Laser Spectrometer (RLS) on Rosalind Franklin, will comprise the first ever in situ planetary mission Raman spectroscopy instruments to identify rocks, minerals, and potential organic biosignatures on Mars' surface. There are many challenges associated when using Raman instruments and the optimization and quantitative analysis of resulting data. To understand how best to overcome them, we performed a comprehensive Raman analysis campaign on CanMars, a Mars sample caching rover analog mission undertaken in Hanksville, Utah, USA, in 2016. The Hanksville region presents many similarities to Oxia Planum's past habitable conditions, including liquid water, flocculent, and elemental compounds (such as clays), catalysts, substrates, and energy/food sources for life. We sampled and conducted a complete band analysis of Raman spectra as mission validation analysis with the RLS ExoMars Simulator or RLS Sim, a breadboard setup representative of the ExoMars RLS instrument. RLS Sim emulates the operational behavior of RLS on the Rosalind Franklin rover. Given the high fidelity of the Mars analog site and the RLS Sim, the results presented here may provide important information useful for guiding in situ analysis and sample triage for caching relevant for the Perseverance and Rosalind Franklin missions. By using the RLS Sim on CanMars samples, our measurements detected oxides, sulfates, nitrates, carbonates, feldspars, and carotenoids, many with a higher degree of sensitivity than past results. Future work with the RLS Sim will aim to continue developing and improving the capability of the RLS system in the future ExoMars mission.

Biosignature Preservation Potential in Playa Evaporites: Impacts of Diagenesis and Implications for Mars Exploration.

Assessing biosignature preservation potential (BPP) in ancient habitable environments on Mars is a top NASA priority. We address this goal through the study of Miocene-Pliocene evaporites of the Verde Formation (central Arizona). We assessed the effects of diagenesis on BPP, integrating outcrop-scale observations with six lab analyses: thin-section petrography, X-ray diffraction, Raman spectroscopy, total organic carbon (TOC), electron probe microanalysis (EPMA), and visible to near-infrared (VNIR) reflectance spectroscopy. We recognized five facies and their diagenetic pathways. Two facies included mudstones which contain clusters of displacive growth gypsum (DGG). Early DGG was altered during diagenesis by dissolution forming crystal cavities and later underwent recrystallization, cation substitution, and sulfate dehydration. Another facies was identified by lenticular beds dominated by halite and late diagenetic thenardite (Na2SO4). These pods are overlain by a sequence of interbedded gray and red mudstones which record cyclic oxidation and Fe-oxide cementation. During the Pleistocene, a lacustrine environment developed, accompanied by magnesite cementation of playa mudstones. TOC analyses were used as a proxy for inferring the BPP in each facies. The highest BPP was associated with both red and gray mudstone facies. This study provides a taphonomic framework for playa environments on Earth that record the impacts of diagenesis on BPP, with potential applications to Mars sample return (MSR) missions.

Detecting Kerogen as a Biosignature Using Colocated UV Time-Gated Raman and Fluorescence Spectroscopy.

The Mars 2020 mission will analyze samples in situ and identify any that could have preserved biosignatures in ancient habitable environments for later return to Earth. Highest priority targeted samples include aqueously formed sedimentary lithologies. On Earth, such lithologies can contain fossil biosignatures as aromatic carbon (kerogen). In this study, we analyzed nonextracted kerogen in a diverse suite of natural, complex samples using colocated UV excitation (266 nm) time-gated (UV-TG) Raman and laser-induced fluorescence spectroscopies. We interrogated kerogen and its host matrix in samples to (1) explore the capabilities of UV-TG Raman and fluorescence spectroscopies for detecting kerogen in high-priority targets in the search for possible biosignatures on Mars; (2) assess the effectiveness of time gating and UV laser wavelength in reducing fluorescence in Raman spectra; and (3) identify sample-specific issues that could challenge rover-based identifications of kerogen using UV-TG Raman spectroscopy. We found that ungated UV Raman spectroscopy is suited to identify diagnostic kerogen Raman bands without interfering fluorescence and that UV fluorescence spectroscopy is suited to identify kerogen. These results highlight the value of combining colocated Raman and fluorescence spectroscopies, similar to those obtainable by SHERLOC on Mars 2020, to strengthen the confidence of kerogen detection as a potential biosignature in complex natural samples. Key Words: Raman spectroscopy-Laser-induced fluorescence spectroscopy-Mars Sample Return-Mars 2020 mission-Kerogen-Biosignatures. Astrobiology 18, 431-453.

FIRE - Flyby of Io with Repeat Encounter: A conceptual design for a New Frontiers mission to Io.

A conceptual design is presented for a low complexity, heritage-based flyby mission to Io, Jupiter's innermost Galilean satellite and the most volcanically active body in the Solar System. The design addresses the 2011 Decadal Surveys recommendation for a New Frontiers class mission to Io and is based upon the result of the June 2012 NASA-JPL Planetary Science Summer School. A science payload is proposed to investigate the link between the structure of Io's interior, it's volcanic activity, it's surface composition, and it's tectonics. A study of Io's atmospheric processes and Io's role in the Jovian magnetosphere is also planned. The instrument suite includes a visible/near IR imager, a magnetic field and plasma suite, a dust analyzer and a gimbaled high gain antenna to perform radio science investigations. Payload activity and spacecraft operations would be powered by three Advanced Stirling Radioisotope Generators (ASRG). The primary mission includes 10 flybys with close-encounter altitudes as low as 100 km. The mission risks are mitigated by ensuring that relevant components are radiation tolerant and by using redundancy and flight-proven parts in the design. The spacecraft would be launched on an Atlas V rocket with a delta-v of 1.3 km/s. Three gravity assists (Venus, Earth, Earth) would be used to reach the Jupiter system in a 6-year cruise. The resulting concept demonstrates the rich scientific return of a flyby mission to Io.