Distribution of Temperature and Strength in the Central Andean Lithosphere and Its Relationship to Seismicity and Active Deformation

We present three-dimensional (3D) models of the present-day steady-state conductive thermal field and strength distribution in the lithosphere beneath the Central Andes. Our primary objective was to investigate the influence that the structure of the Central Andean lithosphere has on its thermal and rheological state, and the relationship between the latter and the active deformation in the region. We used our previous data-driven and gravity-constrained 3D density model as starting point for the calculations. We first assigned lithology-derived thermal and rheological properties to the different divisions of the density model and defined temperature boundary conditions. We then calculated the 3D steady-state conductive thermal field and the maximum differential stresses for both brittle and ductile behaviors. We find that the thickness and composition of the crust are the main factors affecting the modeled thermal field, and consequently also the strength distribution. The orogen is characterized by a thick felsic crust with elevated temperatures and a low integrated strength, whereas the foreland and forearc are underlain by a more mafic and thinner crust with lower temperatures and a higher integrated strength. We find that most of the intraplate deformation coincides spatially with the steepest strength gradients and suggest that the high potential energy of the orogen together with the presence of rheological lateral heterogeneities produce high compressional stresses and strong strain localization along the margins of the orogen. We interpret earthquakes within the modeled ductile field to be related to the weakening effect of long-lived faults and/or the presence of seismic asperities.Fil: Ibarra, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Prezzi, Claudia Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Bott, Judith. German Research Centre for Geosciences; AlemaniaFil: Scheck Wenderoth, Magdalena. German Research Centre for Geosciences; AlemaniaFil: Strecker, Manfred. Universitat Potsdam; Alemani

Impact of UV C exposure on the water retention of the lichen Buellia frigida

New results on extremophiles and observations of Mars missions regarding the detailed mineralogy, the occurrence of water in the equatorial region of Mars [1-3], new announcements of MSL findings and their implications for the surface condi-tions at Gale crater [4, 5] as well as measurements of the Mars surface radiation environment [6] fuel the debate about possible developments of life on Mars. Based on previous studies [7-8] we examined water vapor interaction and water-bearing properties of B. frigida before and after UVC irradiation. The meas-urements have been partially conducted after simula-tion of environmental conditions which are supposed to be Mars-like. Lichens are symbiotic organisms that are able to colonize a broad range of extreme habitats and, therefore, represent useful model systems in as-trobiological research. Our aim is to contribute to an improved under-standing of extremophiles under exobiological aspects within the frame of BIOMEX (Biology and Mars Ex-periment) at the ISS, in respect to irradiation effects on water retention properties. The results may also sup-port data evaluation of in-situ missions such as MSL and ExoMars. References: [1] Feldmann W.C. et al. (2004) JGR 109 E 09006. [2] Bibring, J.-P. et al. Science 307, 1576-1581. [3] Poulet F. et al. (2005) Nature 438, 623- 627. [4] Vaniman D.T. et al. (2013) Science DOI: 10.1126/science.1243480. [5] Ming D.W. et al. (2013) Science DOI: 10.1126/science.1245267 [6] Hassler D.M. et al. (2013) Science DOI: 10.1126/science. 1244797.[7] Jänchen J. et al. (2006) Icarus, 180, 353- 358. [8] Jänchen J. et al. (2013) 44th LPSC Abstract No. 1504

Humidity interaction of lichens under astrobiological aspects: the impact of UVC exposure on their water retention properties

We quantitatively studied the hydration and dehydration behaviour of the three astrobiological model lichens Xanthoria elegans, Buellia frigida and Circinaria gyrosa by thermoanalysis and gravimetric isotherm measurements under close-to-Martian environmental conditions in terms of low temperature and low pressure. Additionally, the impact of UVC exposure on the isolated symbionts of B. frigida and X. elegans was studied by thermoanalysis and mass spectrometry as well as by gravimetric isotherm measurements. The thermal analysis revealed whewellite as a component of C. gyrosa which was not found in B. frigida and X. elegans. Neither the water retention nor the thermal behaviour of symbionts changed when irradiated with UVC under dry conditions. On the other hand, UVC irradiation of the wet mycobiont of B. frigida had a distinct impact on the hydration/dehydration ability which was not observed for the mycobiont of X. elegans. Possibly the melanin of B. frigida’s mycobiont, that is not present in X. elegans, or a specifically damaged acetamido group of the chitin of B. frigida may be the sources of additional UVCinduced sorption sites for water associated with the UVC exposure

Lichens survived ground simulation tests before integration on board of the EXPOSE R2 mission

Ground simulation tests are necessary for selection of the most promising biological organisms for flight experiments in Low Earth Orbit or other space destinations: Simulation of the environmental parameters of the mission, as well as of sample assembly and disassembly, need to be performed, allowing the qualification of the experiment and facilitating the post-flight analysis of the exposed biological material and thus, a deeper understanding of the individual and synergistic effects of space. This work is a presentation of the results obtained with the lichen species Circinaria gyrosa, after the Experiment Verification tests (EVT) and Space Verification tests (SVT) in the frame of the EXPOSE-R2 Mission Preflight Test Program, performed at DLR (Cologne, Germany), as part of the EXPOSE-R2 Mission Preflight Test Program. The high vitality and resistance capacity of C. gyrosa, demonstrated with the PSII values measured after reactivation in the laboratory and the CLSM (Confocal Laser Scanning Microscopy) results confirm the high survival potential of these species to space and Mars conditions, taking part of the BIOMEX experiment (Biology and Mars Experiment, EXPOSE R-2, ISS, 2016-2018) and contributing to our understanding of extremotolerance and the Lithopanspermia hypothesis