The mechanisms of formation of some small cones in Chryse Planitia on Mars

<p><strong>Introduction: </strong>Small cones are common on Mars. Many cones form subparallel chains several kilometers in length. Their origin is discussed in many papers, however, the mechanism of their formation is not explained [1].</p><p>In the present paper, we deal with a small region in Chryse Planitia ( ~38<sup>o</sup>13′ N and ~319<sup>o</sup>25’ E). The region is covered by lacustrine deposits.</p><p>    On Mars, chains of small cones occupy vast areas. Therefore, we try to explain the existence of the chains by specific conditions on Mars. We focus on the hypothesis connecting the formation of cones with the loss of water from the regolith due its instability. See e.g. [1], [2], [4], [5].</p><p><strong> </strong></p><p><strong>Mechanism of cones formation: </strong>We consider 3 mechanisms of cone formation: (i) a grains’ ejection, (ii) from mud or fluidized sand and (iii) explosive formation. The (iii) and (ii) are possible with additional heat sources only.</p><p>    Assuming that only heat of melting was used for vaporization, then only ~13% of liquid water will be vaporized, If the outgassing effect is to be regolith without water, then there must be also other heat sources. Therefore we consider two coexisting factors required for cones formation: (1) the presence of water in the regolith and (2) some additional heating, e.g. magma intrusion.</p><p>    The formation of a chain of cones is possible in two situations:</p><p>(a) above a linear structure containing water and areal heating. Outcrops of aquifers could serve as linear sources of volatiles.</p><p>(b) above a linear source of magmatic heat and the areal aquifer. A dike could serve as linear source of heat.</p><p><strong> </strong></p><p><strong>Conclusions and future plans;</strong></p><p>1) Considered cones could be a result of outgassing of regolith due to pressure drop.</p><p>2) Subparallel chains of cones were formed along the outcrops of volatile-rich sediments.</p><p>3) Numerical modeling indicates that small magma intrusions may not be enough for completely degassing some aquifers.</p><p><strong> </strong></p><p><strong>Acknowledgments:</strong> This study was supported by statutory project of Institute of Geophysics of University of Warsaw. We are also grateful to prof. W. Kofman and dr. J. Ciążela for their remarks.</p><p><strong> </strong></p><p><strong>References</strong></p><p>[1] Fagents, S., Thordarson, T., (2007) The Geology of Mars: Evidence from Earth-Based Analogs, ed. Mary Chapman. Cambridge Univ. Press. [2] Brož,, et al. (2019) JGR: Planets. 124, 703–720. [3] Rotto, S., Tanaka, K. L. (1995) Geologic/ geomorphologic map of the Chryse Planitia: region of Mars. USGS. [4] Barlow, N.G. (2010) GSA Bulletin (2010) 122 (5-6): 644–657. [5] Brož, P., et al. (2020) Nature Geoscience. 13, 403–407.</p>

IMPROVED ANISOTROPIC LINEAR SOURCE FORMULATION FOR MULTIPHYSICS PROBLEMS

This work seeks to extend an existing formulation of the method of characteristics with linear source approximation for problems with dynamic cross sections. The previous formulation eliminated cross section dependence of precomputed coefficients for systems with an isotropic source. The method is extended to include a formulation for spatially flat anisotropic scattering that eliminates cross section dependence of precomputed coefficients without adding additional operations; increasing efficiency in multiphysics simulations where cross sections can be subject to change. The new formulation is implemented in the MPACT code and tested on two problems: 3D transport assembly calculations using MPACT’s 2D/1D method and a 3D assembly with T/H feedback using MPACT’s 2D/1D method coupled with COBRA-TF. This work demonstrates that the new linear source formulation allows for the number of mesh elements to be significantly reduced while maintaining accuracy, leading to shorter run-times for 3D cases with fixed cross sections, and substantial reduction of memory usage for 3D cases with fixed cross sections. The multiphysics calculations show similar runtimes for the same accuracy with significant reduction of memory. For similar accuracy, the method proved effective in reducingmemory usage by, on average, 30% for 3D problems and 21% for multiphysics problems.

Existence and asymptotic profiles of the steady state for a diffusive epidemic model with saturated incidence and spontaneous infection mechanism

<p style='text-indent:20px;'>In this paper, we are concerned with a reaction-diffusion SIS epidemic model with saturated incidence rate, linear source and spontaneous infection mechanism. We derive the uniform bounds of parabolic system and obtain the global asymptotic stability of the constant steady state in a homogeneous environment. Moreover, the existence of the positive steady state is established. We mainly analyze the effects of diffusion, saturation and spontaneous infection on the asymptotic profiles of the steady state. These results show that the linear source and spontaneous infection can enhance the persistence of an infectious disease. Our mathematical approach is based on topological degree theory, singular perturbation technique, the comparison principles for elliptic equations and various elliptic estimates.</p>

Non-linear source term and scenario for an operational oil spill model

This study presents time-varying oil spill discharge functions and scenarios for operational oil spill models. This study prescribes non-linear models based on experimental measurements (Tavakoli et al. in Ocean Eng 38(17–18):1894–1907, 2011) and then upscaled to the spill duration and discharge quantity for actual oil spill incidents. Scenarios consist in collision and grounding incidents for the instantaneous spill mode; light, medium, and severe incidents for the continuous spill mode; spilt, containment, and retention practices for the spill management mode. A performance analysis of deterministic simulations indicates that the non-linear source terms and scenarios present realistic and reasonable results, showing the detailed spill patterns on the surface ocean, tail-off oil sheens along the areas swept by the dispersion and significantly different results when oil spill management and mitigation practices are activated. For oil spill modelling in support of field operations, responders and decision makers should be made aware of the variability of oil sheen spatial patterns induced by the oil spill source term to better interpret simulation results and assess the impact of source uncertainty on the clean-up, mitigation, ecological and socio-economic risk.