Limits of life and the habitability of Mars: The ESA space experiment BIOMEX on the ISS

BIOMEX (BIOlogy and Mars EXperiment) is an ESA/Roscosmos space exposure experiment housed within the exposure facility EXPOSE-R2 outside the Zvezda module on the International Space Station (ISS). The design of the multiuser facility supports—among others—the BIOMEX investigations into the stability and level of degradation of space-exposed biosignatures such as pigments, secondary metabolites, and cell surfaces in contact with a terrestrial and Mars analog mineral environment. In parallel, analysis on the viability of the investigated organisms has provided relevant data for evaluation of the habitability of Mars, for the limits of life, and for the likelihood of an interplanetary transfer of life (theory of lithopanspermia). In this project, lichens, archaea, bacteria, cyanobacteria, snow/permafrost algae, meristematic black fungi, and bryophytes from alpine and polar habitats were embedded, grown, and cultured on a mixture of martian and lunar regolith analogs or other terrestrial minerals. The organisms and regolith analogs and terrestrial mineral mixtures were then exposed to space and to simulated Mars-like conditions by way of the EXPOSE-R2 facility. In this special issue, we present the first set of data obtained in reference to our investigation into the habitability of Mars and limits of life. This project was initiated and implemented by the BIOMEX group, an international and interdisciplinary consortium of 30 institutes in 12 countries on 3 continents. Preflight tests for sample selection, results from ground-based simulation experiments, and the space experiments themselves are presented and include a complete overview of the scientific processes required for this space experiment and postflight analysis. The presented BIOMEX concept could be scaled up to future exposure experiments on the Moon and will serve as a pretest in low Earth orbit

Preservation of carotenoids in salts and Mars regolith in various conditions

The search for life on Mars requires new tools and techniques. Among them, Raman spectroscopy is a powerful and non-destructive method for detecting biosignatures during missions to Mars such as NASA’s Perseverance and ESA/ROSCOSMOS’s Rosalind Franklin rovers. It is therefore important to study the detection possibilities of model biosignatures and their preservation in various conditions over time in order to guide future missions and interpret future data. Cyanobacterial photoprotective pigments (namely carotenoids) have been extensively used as suited targets for such measurements and to serve as biosignature models thanks to their stability and easy identification by Raman spectroscopy. Carotenoid decomposition can be caused by oxidation1 (prevented by higher humidity) and irradiation (prevented by lower humidity2). Carotenoids seem to be decomposing at different rates in different sets of conditions and on different matrices. During the preparation phase of BioSigN (BioSignatures and habitable Niches) we explore the possibility that different matrices enhance or diminish preservation of detectable carotenoid signal under different storage conditions. Both pure molecular β-carotene and cyanobacterium Nostoc sp. (strain CCCryo 231-06) were used

Leadership succession as an aspect of organisational sustainability in complementary schools in England

The article explores leadership succession as an aspect of organizational sustainability in complementary schools in England as an example of how schools in precarious circumstances seek to ensure their survival and growth. Complementary schools offer part time educational provision outside of mainstream, state-funded school systems in many countries. Often established by migrant and minority ethnic groups to teach language, culture, religion and/or to consolidate state school learning, a lack of resources can threaten their stability and development. We analyse data collected from ten Brazilian and Chinese complementary school leaders in England using concepts from organizational sustainability and leadership succession planning. Our focus on the little researched context of complementary schools adds to the understanding of leading and managing in distinctive and challenging circumstances. Their inclusion in the debates and research can foster different insights into the ways that schools in diverse and challenging contexts seek to ensure their survival and growth

Optically pump-induced athermal and nonresonant refractive index changes in the reference Cr-doped laser materials: Cr:GSGG and ruby

The refractive index of most ion-doped materials increases with the excited state population. This effect was studied in many laser materials, particularly those doped with 'Cr POT. 3+' and rare earth ions, using several techniques, such as interferometry, wave mixing, and Z-scans. This refractive index variation is athermal (has an electronic origin) and is associated with the difference in the polarizabilites of the 'Cr POT. 3+' ion in its excited and ground states, 'delta''alfa IND. p'. The 'Cr POT. 3+' optical transitions in the visible domain are electric-dipole forbidden, and they have low oscillator strengths. Therefore, the major contribution to 'delta''alfa IND. p' has been assigned to allowed transitions to charge transfer bands (CTBs) in the UV with strengths 'DA ORDEM DE' 3 orders of magnitude higher. Although this CTB model qualitatively explains the main observations, it was never quantitatively tested. In order to further investigate the physical origin of 'delta''alfa IND. p' in 'Cr POT. 3+'-doped crystals, excited state absorption (ESA) and Z-scan measurements were thus performed in Cr:'Al IND. 2''O IND. 3' (ruby) and Cr:GSGG. Cr:GSGG was selected because of the proximity of its 'ANTPOT. 2 E' and '4 ANTPOT. T IND. 2' emitting levels, and thus the possibility to explore the role of the spin selection rule in the ESA spectra and the resulting variations in polarizability by comparing low and room temperature data, which were never reported before.On the other hand, Cr:'Al IND. 2''O IND. 3'(ruby) was selected because it is the only crystal for which it is possible to obtain CTB absorption data from both ground and excited states, and thus for which it is possible to check the CTB model more accurately. Thanks to these more accurate and more complete data, we came to the first conclusion that the spin selection rule does not play any significant role in the variation of the polarizability with the 'ANTPOT. 2 E'-'4 ANTPOT. T IND. 2' energy mismatch. We also discovered that using the CTB model in the case of ruby would lead to a negative 'delta''alfa IND. p' value, which is contrary to all refractive index variation (including Z-scan) measurements

Anatomy and function of the vertebral column lymphatic network in mice

Cranial lymphatic vessels (LVs) are involved in the transport of fluids, macromolecules and central nervous system (CNS) immune responses. Little information about spinal LVs is available, because these delicate structures are embedded within vertebral tissues and difficult to visualize using traditional histology. Here we show an extended vertebral column LV network using three-dimensional imaging of decalcified iDISCO(+)-clarified spine segments. Vertebral LVs connect to peripheral sensory and sympathetic ganglia and form metameric vertebral circuits connecting to lymph nodes and the thoracic duct. They drain the epidural space and the dura mater around the spinal cord and associate with leukocytes. Vertebral LVs remodel extensively after spinal cord injury and VEGF-C-induced vertebral lymphangiogenesis exacerbates the inflammatory responses, T cell infiltration and demyelination following focal spinal cord lesion. Therefore, vertebral LVs add to skull meningeal LVs as gatekeepers of CNS immunity and may be potential targets to improve the maintenance and repair of spinal tissues.Peer reviewe