Life Detection Knowledge Base: Taxonomy of Potential Biosignatures.

The Life Detection Knowledge Base (LDKB) is a community webtool developed to test and evaluate strategies to search for evidence of life beyond Earth, with an emphasis on recognizing potential false-positive and false-negative results. As part of the LDKB framework, we developed a taxonomy of potential biosignatures. The taxonomy brings together a broad array of life-detection strategies into a common and systematic structure that allows for equitable evaluations based on a specific set of criteria, chosen to assess the likelihood of false-positive and false-negative interpretations.

Life Detection Knowledge Base: Assessment Criteria for Potential Biosignatures.

Astrobiology and the search for evidence of life beyond Earth are now key drivers for planetary science and astronomy missions. Efforts are underway to establish evaluative frameworks to interpret potential signs of life in returned data. However, there is a need for a "before-the-fact" system to assess mission science risk and the potential false negative and false positive results.

Life Detection Knowledge Base: A Community Tool for Knowledge Management and Representation.

The Life Detection Knowledge Base (LDKB; https://lifedetectionforum.com/ldkb) is a community-owned web resource that is designed to facilitate the infusion of astrobiology knowledge and expertise into the conceptualization and design of life detection missions. The aim of the LDKB is to gather and organize diverse knowledge from a range of fields into a common reference frame to support mission science risk assessment, specifically in terms of the potential for false positive and false negative results when pursuing a particular observation strategy.

Photochemical Evolution of Alanine in Association with the Martian Soil Analog Montmorillonite: Insights Derived from Experiments Conducted on the International Space Station.

The (PSS) experiment was part of the European Space Agency's mission and was conducted on the International Space Station from 2014 to 2016. The PSS experiment investigated the properties of montmorillonite clay as a protective shield against degradation of organic compounds that were exposed to elevated levels of ultraviolet (UV) radiation in space. Additionally, we examined the potential for montmorillonite to catalyze UV-induced breakdown of the amino acid alanine and its potential to trap the resulting photochemical byproducts within its interlayers.

Future of the Search for Life: Workshop Report.

The 2-week, virtual Future of the Search for Life science and engineering workshop brought together more than 100 scientists, engineers, and technologists in March and April 2022 to provide their expert opinion on the interconnections between life-detection science and technology. Participants identified the advances in measurement and sampling technologies they believed to be necessary to perform searches for life elsewhere in our Solar System, 20 years or more in the future. Among suggested measurements for these searches, those pertaining to three potential indicators of life termed "dynamic disequilibrium," "catalysis," and "informational polymers" were identified as particularly promising avenues for further exploration.

A Mission Simulating the Search for Life on Mars with Automated Drilling, Sample Handling, and Life Detection Instruments Performed in the Hyperarid Core of the Atacama Desert, Chile.

We report on a field demonstration of a rover-based drilling mission to search for biomolecular evidence of life in the arid core of the Atacama Desert, Chile. The KREX2 rover carried the Honeybee Robotics 1 m depth The Regolith and Ice Drill for Exploration of New Terrains (TRIDENT) drill and a robotic arm with scoop that delivered subsurface fines to three flight prototype instruments: (1) The Signs of Life Detector (SOLID), a protein and biomolecule analyzer based on fluorescence sandwich microarray immunoassay; (2) the Planetary Capillary Electrophoresis System (PISCES), an amino acid analyzer based on subcritical water extraction coupled to microchip electrophoresis analysis; and (3) a Wet Chemistry Laboratory cell to measure soluble ions using ion selective electrodes and chronopotentiometry. A California-based science team selected and directed drilling and sampling of three sites separated by hundreds of meters that included a light-toned basin area showing evidence of aqueous activity surrounded by a rocky desert pavement.

Increased Bone Formation and Accelerated Bone Mass Accrual in a Man Presenting with Diffuse Osteosclerosis/High Bone Mass Phenotype and Adenocarcinoma of Unknown Primary.

A 71-year-old man was referred for evaluation of incidental generalized osteosclerosis. He was found to have a high bone mass (HBM) with an elevated lumbar spine bone mineral density (BMD) Z-score of +5.3.

Future space experiment platforms for astrobiology and astrochemistry research.

Space experiments are a technically challenging but a scientifically important part of astrobiology and astrochemistry research. The International Space Station (ISS) is an excellent example of a highly successful and long-lasting research platform for experiments in space, that has provided a wealth of scientific data over the last two decades. However, future space platforms present new opportunities to conduct experiments with the potential to address key topics in astrobiology and astrochemistry.

A gravity-independent single-phase electrode reservoir for capillary electrophoresis applications.

Capillary electrophoresis (CE) holds great promise as an in situ analytical technique for a variety of applications. However, typical instrumentation operates with open reservoirs (e.g.

Does Choice of Patellar Implant in Total Knee Arthroplasty Matter?: A Randomized Comparative Trial of 3 Commonly Used Designs.

Background: There is currently a lack of evidence to identify the optimal patellar implant design in total knee arthroplasty (TKA). The aim of this study was to assess clinical, intraoperative, radiographic, and scintigraphic differences between inlay (IN), onlay round (OR), and onlay oval (OO) patellar implants.

Methods: A parallel-group, double-blinded, randomized trial compared IN, OR, and OO patellar implants using the same posterior-stabilized TKA prosthesis for each.

Report of the Joint Workshop on Induced Special Regions.

The Joint Workshop on Induced Special Regions convened scientists and planetary protection experts to assess the potential of inducing special regions through lander or rover activity. An Induced Special Region is defined as a place where the presence of the spacecraft could induce water activity and temperature to be sufficiently high and persist for long enough to plausibly harbor life. The questions the workshop participants addressed were: (1) What is a safe stand-off distance, or formula to derive a safe distance, to a purported special region? (2) Questions about RTGs (Radioisotope Thermoelectric Generator), other heat sources, and their ability to induce special regions.

The Oxygen Release Instrument: Space Mission Reactive Oxygen Species Measurements for Habitability Characterization, Biosignature Preservation Potential Assessment, and Evaluation of Human Health Hazards.

We describe the design of an instrument, the OxR (for Oxygen Release), for the enzymatically specific and non-enzymatic detection and quantification of the reactive oxidant species (ROS), superoxide radicals (O), and peroxides (O, e.g., HO) on the surface of Mars and Moon.

Radiation-Driven Formation of Reactive Oxygen Species in Oxychlorine-Containing Mars Surface Analogues.

The present study demonstrates that γ-radiolyzed perchlorate-containing Mars soil salt analogues (in a CO atmosphere) generate upon HO wetting the reactive oxygen species (ROS) superoxide radical (O), hydrogen peroxide (HO), and hydroxyl radicals (OH). This study also validates that analogue radiolysis forms oxychlorine species that, in turn, can UV-photolyze to OH upon UV photolysis. This investigation was made possible by the development of a new assay for inorganic-origin O and HO determination and by the modification of a previous assay for soil OH.

Martian Superoxide and Peroxide O2 Release (OR) Assay: A New Technology for Terrestrial and Planetary Applications.

This study presents an assay for the detection and quantification of soil metal superoxides and peroxides in regolith and soil. The O2 release (OR) assay is based on the enzymatic conversion of the hydrolysis products of metal oxides to O2 and their quantification by an O2 electrode based on the stoichiometry of the involved reactions. The intermediate product O₂˙⁻ from the hydrolysis of metal superoxides is converted by cytochrome c to O2 and by superoxide dismutase (SOD) to ½ mol O2 and ½ mol H2O2, which is then converted by catalase (CAT) to ½ mol O2.

Spectral and thermal properties of perchlorate salts and implications for Mars.

K, Na, Ca, Mg, Fe, Fe, and Al perchlorate salts were studied to provide spectral and thermal data for detecting and characterizing their possible presence on Mars. Spectral and thermal analyses are coordinated with structural analyses to understand how different cations and different hydration levels affect the mineral system. Near-infrared (NIR) spectral features for perchlorates are dominated by HO bands that occur at 0.

Organics Exposure in Orbit (OREOcube): A next-generation space exposure platform.

The OREOcube (ORganics Exposure in Orbit cube) experiment on the International Space Station (ISS) will investigate the effects of solar and cosmic radiation on organic thin films supported on inorganic substrates. Probing the kinetics of structural changes and photomodulated organic-inorganic interactions with real-time in situ UV-visible spectroscopy, this experiment will investigate the role played by solid mineral surfaces in the (photo)chemical evolution, transport, and distribution of organics in our solar system and beyond. In preparation for the OREOcube ISS experiment, we report here laboratory measurements of the photostability of thin films of the 9,10-anthraquinone derivative anthrarufin (51 nm thick) layered upon ultrathin films of iron oxides magnetite and hematite (4 nm thick), as well as supported directly on fused silica.

The Organism/Organic Exposure to Orbital Stresses (O/OREOS) satellite: radiation exposure in low-earth orbit and supporting laboratory studies of iron tetraphenylporphyrin chloride.

We report results from the exposure of the metalloporphyrin iron tetraphenylporphyrin chloride (FeTPPCl) to the outer space environment, measured in situ aboard the Organism/Organic Exposure to Orbital Stresses nanosatellite. FeTPPCl was exposed for a period of 17 months (3700 h of direct solar exposure), which included broad-spectrum solar radiation (∼122 nm to the near infrared). Motivated by the potential role of metalloporphyrins as molecular biomarkers, the exposure of thin-film samples of FeTPPCl to the space environment in low-Earth orbit was monitored in situ via ultraviolet/visible spectroscopy and reported telemetrically.

Perchlorate radiolysis on Mars and the origin of martian soil reactivity.

Results from the Viking biology experiments indicate the presence of reactive oxidants in martian soils that have previously been attributed to peroxide and superoxide. Instruments on the Mars Phoenix Lander and the Mars Science Laboratory detected perchlorate in martian soil, which is nonreactive under the conditions of the Viking biology experiments. We show that calcium perchlorate exposed to gamma rays decomposes in a CO2 atmosphere to form hypochlorite (ClO(-)), trapped oxygen (O2), and chlorine dioxide (ClO2).

The Icebreaker Life Mission to Mars: a search for biomolecular evidence for life.

The search for evidence of life on Mars is the primary motivation for the exploration of that planet. The results from previous missions, and the Phoenix mission in particular, indicate that the ice-cemented ground in the north polar plains is likely to be the most recently habitable place that is currently known on Mars. The near-surface ice likely provided adequate water activity during periods of high obliquity, ≈ 5 Myr ago.

The O/OREOS mission: first science data from the space environment viability of organics (SEVO) payload.

We report the first science results from the Space Environment Viability of Organics (SEVO) payload aboard the Organism/Organic Exposure to Orbital Stresses (O/OREOS) free-flying nanosatellite, which completed its nominal spaceflight mission in May 2011 but continues to acquire data biweekly. The SEVO payload integrates a compact UV-visible-NIR spectrometer, utilizing the Sun as its light source, with a 24-cell sample carousel that houses four classes of vacuum-deposited organic thin films: polycyclic aromatic hydrocarbon (PAH), amino acid, metalloporphyrin, and quinone. The organic films are enclosed in hermetically sealed sample cells that contain one of four astrobiologically relevant microenvironments.

Hepatic resection with or without adjuvant iodine-131-lipiodol for hepatocellular carcinoma: a comparative analysis.

Background: Resection of hepatocellular carcinoma (HCC) is potentially curative; however, recurrence is common. To date, few or no effective adjuvant therapies have been adequately investigated. This study evaluates the efficacy of adjuvant iodine-131-lipiodol after hepatic resection through the experience of a single-center hepatobiliary service of managing this disease.

Intra-arterial iodine-131-lipiodol for unresectable hepatocellular carcinoma.

Background: Hepatic artery administration of iodine-131-Lipiodol serves as a modality that delivers targeted radiation therapy to hepatocellular carcinoma. Its efficacy has been promising according to trials conducted in the adjuvant setting after hepatic resection. Further investigation of its role in the palliative setting is warranted.

The Urey instrument: an advanced in situ organic and oxidant detector for Mars exploration.

The Urey organic and oxidant detector consists of a suite of instruments designed to search for several classes of organic molecules in the martian regolith and ascertain whether these compounds were produced by biotic or abiotic processes using chirality measurements. These experiments will also determine the chemical stability of organic molecules within the host regolith based on the presence and chemical reactivity of surface and atmospheric oxidants. Urey has been selected for the Pasteur payload on the European Space Agency's (ESA's) upcoming 2013 ExoMars rover mission.