Mimicking Martian dust: An in-vacuum dust deposition system for testing the ultraviolet sensors on the Curiosity rover

Survival of an Antarctic cyanobacterial mat under Martian conditions

Antarctica is one of the most outstanding analogs of Mars, and cyanobacterial mats are considered one of the most resilient biological consortia. The purpose of this study is to find out the effect of the Martian conditions on an Antarctic cyanobacterial mat. We exposed an Antarctic microbial mat to Martian conditions in a simulating chamber (MARTE) for 15 d and investigated the variations in the consortium by the use of 16S rRNA gene expression as an indicator of the biological activity. Metabarcoding using the V3-V4 regions of the 16S rRNA gene was used to determine the succession of the active members of the microbial consortium during the experiment. The results showed that the microbial mat, far from collapsing, can survive the stringent conditions in the simulating chamber. Different behaviors were displayed depending on the metabolic capabilities and physiological characteristics of every taxon. The main conclusion is that the Martian conditions did not impair growth in some of the groups, and thus, the investigated Antarctic community would be able to survive in a Martian environment at least during the short experimental period, although elements of the community were affected in different ways.

The Knudsen Paradox in Micro-Channel Poiseuille Flows with a Symmetric Particle

The Knudsen paradox—the non-monotonous variation of mass-flow rate with the Knudsen number—is a unique and well-established signature of micro-channel rarefied flows. A particle which is not of insignificant size in relation to the duct geometry can significantly alter the flow behavior when introduced in such a system. In this work, we investigate the effects of a stationary particle on a micro-channel Poiseuille flow, from continuum to free-molecular conditions, using the direct simulation Monte-Carlo (DSMC) method. We establish a hydrodynamic basis for such an investigation by evaluating the flow around the particle and study the blockage effect on the Knudsen paradox. Our results show that with the presence of a particle this paradoxical behavior is altered. The effect is more significant as the particle becomes large and results from a shift towards relatively more ballistic molecular motion at shorter geometrical distances. The need to account for combinations of local and non-local transport effects in modeling reactive gas–solid flows in confined geometries at the nano-scale and in nanofabrication of model pore systems is discussed in relation to these results.

INFRA-ICE: An ultra-high vacuum experimental station for laboratory astrochemistry

Laboratory astrochemistry aims at simulating, in the laboratory, some of the chemical and physical processes that operate in different regions of the universe. Amongst the diverse astrochemical problems that can be addressed in the laboratory, the evolution of cosmic dust grains in different regions of the interstellar medium (ISM) and its role in the formation of new chemical species through catalytic processes present significant interest. In particular, the dark clouds of the ISM dust grains are coated by icy mantles and it is thought that the ice-dust interaction plays a crucial role in the development of the chemical complexity observed in space. Here, we present a new ultra-high vacuum experimental station devoted to simulating the complex conditions of the coldest regions of the ISM. The INFRA-ICE machine can be operated as a standing alone setup or incorporated in a larger experimental station called Stardust, which is dedicated to simulate the formation of cosmic dust in evolved stars. As such, INFRA-ICE expands the capabilities of Stardust allowing the simulation of the complete journey of cosmic dust in space, from its formation in asymptotic giant branch stars to its processing and interaction with icy mantles in molecular clouds. To demonstrate some of the capabilities of INFRA-ICE, we present selected results on the ultraviolet photochemistry of undecane (C₁₁H₂₄) at 14 K. Aliphatics are part of the carbonaceous cosmic dust, and recently, aliphatics and short n-alkanes have been detected in situ in the comet 67P/Churyumov-Gerasimenko.

Mimicking the Martian Hydrological Cycle: A Set-Up to Introduce Liquid Water in Vacuum

Liquid water is well known as the life ingredient as a solvent. However, so far, it has only been found in liquid state on this planetary surface. The aim of this experiment and technological development was to test if a moss sample is capable of surviving in Martian conditions. We built a system that simulates the environmental conditions of the red planet including its hydrological cycle. This laboratory facility enables us to control the water cycle in its three phases through temperature, relative humidity, hydration, and pressure with a system that injects water droplets into a vacuum chamber. We successfully simulated the daytime and nighttime of Mars by recreating water condensation and created a layer of superficial ice that protects the sample against external radiation and minimizes the loss of humidity due to evaporation to maintain a moss sample in survival conditions in this extreme environment. We performed the simulations with the design and development of different tools that recreate Martian weather in the MARTE simulation chamber.

Complete degradation of ciprofloxacin over g-C3N4-iron oxide composite via heterogeneous dark Fenton reaction

Graphitic carbon nitride (g-C₃N₄) supported iron oxide (CN@IO) composite was first fabricated via synthesizing g-C₃N₄ in-situ onto iron oxide. The fabricated CN@IO composite was characterized by several techniques including XRD, XPS, TEM and nitrogen adsorption-desorption analysis. This composite was then used as a catalyst for the dark Fenton oxidative degradation of ciprofloxacin (CIP). Results demonstrated that the incorporation of g-C₃N₄ profoundly changed the structure and chemical properties of iron oxide, endowing CN@IO composites with high-efficient catalytic activity in dark Fenton system. In the synthesis process of CN@IO composites, iron oxide nanoparticles were successfully intercalated into the layers of g-C₃N₄, enlarging the surface area and thus providing more active sites for the reactions. Meanwhile, the existence of g-C₃N₄ can accelerate the Fe³⁺/Fe²⁺ redox cycle during the Fenton reaction, which further facilitated CIP degradation. In addition, the effects of reaction parameters, including pH, catalyst dosage, initial concentration of CIP and H₂O₂, on CIP degradation were investigated. Without any assistance of light irradiation, complete degradation and 48.5% mineralization of CIP were achieved under the best conditions of pH 3.0, 1 g/L CN@IO-2, 20 mg/L CIP and 0.0056 M H₂O₂. The trapping of iron oxide between g-C₃N₄ layers helped to stabilize iron oxide so the metal leaching problem that usually occurred in acidic media (pH = 3) can be effectively overcome. This work provides a new thought to develop environmental-friendly and high-efficient catalysts for the degradation of refractory pollutants in dark Fenton system, which is much easier to scale up for industrial application comparing with the photo-Fenton reaction.

Venturing into new realms? Microorganisms in space

One of the biggest challenges of science is the determination of whether extraterrestrial life exists. Although potential habitable areas might be available for complex life, it is more likely that microbial life could exist in space. Many extremotolerant and extremophilic microbes have been found to be able to withstand numerous, combined environmental factors, such as high or low temperatures and pressures, high-salt conditions, high doses of radiation, desiccation or nutrient limitations. They may even survive the transit from one planet to another. Terrestrial Mars-analogue sites are one focus of researchers, in order to understand the microbial diversity in preparation for upcoming space missions aimed at the detection of life. However, such missions could also pose a risk with respect to contamination of the extraterrestrial environment by accidentally transferred terrestrial microorganisms. Closer to the Earth, the International Space Station is the most enclosed habitat, where humans work and live-and with them numerous microorganisms. It is still unknown how microbes adapt to this environment, possibly even creating a risk for the crew. Information on the microbiology of the ISS will have an impact on the planning and implementation of long-term human spaceflights in order to ensure a safe, stable and balanced microbiome on board.