In Situ Detection of Kinetic-size Magnetic Holes in the Martian Magnetosheath

Depression in magnetic field strength with a scale below one proton gyroradius is referred to as a kinetic-size magnetic hole (KSMH). KSMHs are frequently observed near Earth’s space environments and are thought to play an important role in electron energization and energy dissipation in space plasmas. Recently, KSMHs have been evidenced in the Venusian magnetosheath. However, observations of KSMHs in other planetary environments are still lacking. In this study, we present the in situ detection of KSMHs in the Martian magnetosheath using Mars Atmosphere and Volatile EvolutioN (MAVEN) for the first time. The distribution of KSMHs is asymmetry in the southern–northern hemisphere and no obvious asymmetry in the dawn–dusk hemisphere. The observed KSMHs are accompanied by increases in the electron fluxes in the perpendicular direction, indicating the cues of trapped electrons and the formation of electron vortices inside KSMHs. These features are similar to the observations in the Earth’s magnetosheath and magnetotail plasma sheet and the Venusian magnetosheath. This implies that KSMHs are a universal magnetic structure in space.

Ammonia synthesis on the banks of the Mississippi: A molecular-planetary technology

The paper discusses the CF-industries ammonia plant in Donaldsonville, Louisiana. The plant is framed as an exemplary site from which the Anthropocene can be observed and understood. In doing so, a proposal for a “chemical cultural theory” is set out, to allow us to understand such molecular planetary technologies and interpret their (geo)historical significance. As one of the largest fertilizer plants in the world in terms of its output, and one of the largest chemical plants along the “Petrochemical Corridor,” a cluster of chemical industries situated between Baton Rouge and New Orleans, Donaldsonville typifies the relations between the nitrogen and hydrocarbon industries. Catalysis is here used both as a chemical concept and as a metaphor central to the proposed chemical cultural theory. As key to the Haber-Bosch process and refinery technologies in general, investigating the role of catalysis allows us to connect the history of the Petrochemical Corridor to that of German industrialism. This relation reveals how, from the late 19th century through to the World Wars, an ambivalent industrial co-operation between the US and Germany not only transformed local and planetary environments, it also contributed to the Anthropocene condition.

An expression for the angle of repose of dry cohesive granular materials on Earth and in planetary environments

The angle of repose—i.e., the angle θr between the sloping side of a heap of particles and the horizontal—provides one of the most important observables characterizing the packing and flowability of a granular material. However, this angle is determined by still poorly understood particle-scale processes, as the interactions between particles in the heap cause resistance to roll and slide under the action of gravity. A theoretical expression that predicts θr as a function of particle size and gravity would have impact in the engineering, environmental, and planetary sciences. Here we present such an expression, which we have derived from particle-based numerical simulations that account for both sliding and rolling resistance, as well as for nonbonded attractive particle–particle interactions (van der Waals). Our expression is simple and reproduces the angle of repose of experimental conical heaps as a function of particle size, as well as θr obtained from our simulations with gravity from 0.06 to 100 times that of Earth. Furthermore, we find that heaps undergo a transition from conical to irregular shape when the cohesive to gravitational force ratio exceeds a critical value, thus providing a proxy for particle-scale interactions from heap morphology.

Europa’s interaction with the jovian plasma from hybrid simulation

<p>Galilean moons are embedded in Jupiter’s giant magnetosphere. The jovian plasma particles interact with the atmosphere of the moons, exchanging momentum and energy, and generate different phenoma such as aurora, electric current, etc.</p> <p>The exploration of the Galilean moons, and in particular Ganymede and Europa considered as potential habitats, are listed among the main objectives of the ESA JUpiter ICy moon Explorer mission. In preparation of future observations, a simulation effort is conducted to describe the Europa moon-magnetosphere system as well as a study of radio wave propagation in the environments of Ganymede and Europa using a ray tracing code.</p> <p>LatHyS is a hybrid 3D, multi-species and parallel simulation model which is based on a kinetic description of ions and a fluid description of electrons. The model is based on the CAM-CL algorithm that Alan Matthews¹ outlined in 1994. It allows to describe the interaction between the jovian plasma and the moon environments. As Ganymede's environment has already been implemented, we propose to enrich the model by completing it with Europa's – jovian plasma interaction and to optimize it in order to improve the accuracy of the results.</p> <p>Artemis-P, developed by Gautier² in 2013, is a ray tracing code that calculates the trajectory of waves through a given environment. Planetary environments are anisotropic and inhomogeneous, so that radio waves can undergo refraction, reflection, scattering, diffraction, interference, etc. between the source and the detector. The ray tracing methods allow to treat the refraction and reflection phenomena at large scales compared to the wavelength. The proposed work is to adjust this program to the environments of Ganymede and Europa using data from LatHyS simulations.</p> <p> </p> <p align="left">Références :</p> <p align="left"><sup>1</sup> Alan P. Matthews, Current Advance Method and Cyclic Leapfrog for 2D Multispecies Hybrid Plasma Simulations, Journal of Computational Physics, Volume 112, Issue 1, 1994, Pages 102-116, ISSN 0021-9991, https://doi.org/10.1006/jcph.1994.1084.</p> <p align="left">² Anne-Lise Gautier. Étude de la propagation des ondes radio dans les environnements planétaires. Planétologie et astrophysique de la terre [astro-ph.EP]. Observatoire de Paris, 2013. Français. tel-01145651v2</p>

Troubled Orbits and Earthly Concerns: Space Debris as a Boundary Infrastructure

Like other forms of debris in terrestrial and marine environments, space debris prompts questions about how we can live with the material remains of technological endeavors past and yet to come. Although techno-societies fundamentally rely on space infrastructures, they so far have failed to address the infrastructural challenge of debris. Only very recently has the awareness of space debris as a severe risk to both space and Earth infrastructures increased within the space community. One reason for this is the renewed momentum of interplanetary space exploration, including the colonization of the Moon and Mars, which is part of transhumanist and commercially driven dreams of the so-called New Space age. Understanding space infrastructures as inherently linked to earthly infrastructure, we attend to the ways in which space debris, a once accepted by-product of scientific-technological progress, economic interests, and geopolitics, increasingly becomes a matter of concern. Drawing on qualitative interviews with European space sector representatives and work in Science and Technology Studies on infrastructures, we argue that their discursive efforts and visual representation strategies coproduce space debris as a boundary infrastructure. We suggest considering this boundary infrastructure as relating orbital environments and the planet through enacting sustainability and responsibility for beyond-planetary environments.