The Suborbital Particle Aggregation and Collision Experiment (SPACE): Studying the Collision Behavior of Submillimeter-Sized Dust Aggregates on the Suborbital Rocket Flight REXUS 12

The Suborbital Particle Aggregation and Collision Experiment (SPACE) is a novel approach to study the collision properties of submillimeter-sized, highly porous dust aggregates. The experiment was designed, built and carried out to increase our knowledge about the processes dominating the first phase of planet formation. During this phase, the growth of planetary precursors occurs by agglomeration of micrometer-sized dust grains into aggregates of at least millimeters to centimeters in size. However, the formation of larger bodies from the so-formed building blocks is not yet fully understood. Recent numerical models on dust growth lack a particular support by experimental studies in the size range of submillimeters, because these particles are predicted to collide at very gentle relative velocities of below 1 cm/s that can only be achieved in a reduced-gravity environment. The SPACE experiment investigates the collision behavior of an ensemble of silicate-dust aggregates inside several evacuated glass containers which are being agitated by a shaker to induce the desired collisions at chosen velocities. The dust aggregates are being observed by a high-speed camera, allowing for the determination of the collision properties of the protoplanetary dust analog material. The data obtained from the suborbital flight with the REXUS (Rocket Experiments for University Students) 12 rocket will be directly implemented into a state-of-the-art dust growth and collision model

NanoRocks: Design and Performance of an Experiment Studying Planet Formation on the International Space Station

In an effort to better understand the early stages of planet formation, we have developed a 1.5U payload that flew on the International Space Station (ISS) in the NanoRacks NanoLab facility between September 2014 and March 2016. This payload, named NanoRocks, ran a particle collision experiment under long-term microgravity conditions. The objectives of the experiment were (a) to observe collisions between mm-sized particles at relative velocities of $<$1~cm/s, and (b) to study the formation and disruption of particle clusters for different particle types and collision velocities. Four types of particles were used: mm-sized acrylic, glass, and copper beads, and 0.75 mm-sized JSC-1 lunar regolith simulant grains. The particles were placed in sample cells carved out of an aluminum tray. This tray was attached to one side of the payload casing with three springs. Every 60~s, the tray was agitated and the resulting collisions between the particles in the sample cells were recorded by the experiment camera. During the 18 months the payload stayed on ISS, we obtained 158 videos, thus recording a great number of collisions. The average particle velocities in the sample cells after each shaking event were around 1 cm/s. After shaking stopped, the inter-particle collisions damped the particle kinetic energy in less than 20~s, reducing the average particle velocity to below 1 mm/s, and eventually slowing them to below our detection threshold. As the particle velocity decreased, we observed the transition from bouncing to sticking collisions. We recorded the formation of particle clusters at the end of each experiment run. This paper describes the design and performance of the NanoRocks ISS payload.Comment: 8 pages, 8 figure

Ein Raketen-Schwerelosigkeitsexperiment zur Untersuchung von Protoplanetaren Staub-Wachstum

In the very first steps of the formation of a new planetary system, dust agglomerates and grows inside the protoplanetary disk that rotates around the newly formed star. In this disk, collisions between the dust particles lead to sticking. Aggregates start growing until their sizes and relative velocities are high enough for collisions to result in bouncing or fragmentation. The Suborbital Particle and Aggregation Experiment (SPACE) was designed, built and operated both at the drop tower in Bremen (August 2011) and on the REXUS 12 suborbital rocket (March 2012) to observe collisions between SiO2 aggregates of sizes of a few 100 µm. The time under microgravity conditions allowed for collision velocities below 1 cm/s. At these low velocities, clusters composed of a high number of aggregates (more than 10^4) formed and grew to sizes of up to 5 mm. The data results showed that the sticking probability of a collision is enhanced for aggregate-cluster and cluster-cluster collisions compared to simple aggregate-aggregate collisions. Furthermore, the sticking probability of sub-mm-sized dust aggregates could directly be measured during the suborbital rocket flight, over a velocity range covering the transition between the sticking and bouncing regimes. It was also shown that the formed clusters are more fragile and fragment at collision velocities as low as 5 cm/s. In addition, the evolution of clusters formed from sub-mm-sized aggregates during the different experiments could be observed and some of their intrinsic properties derived. The measured characteristics were the cluster fractal dimensions, the tensile strength of their outer aggregate layer and the effective surface energy of their constituents. Threshold energies for cluster restructuring and fragmentation could also be determined. All these cluster properties are important input parameters for molecular dynamics or numerical simulations investigating the behavior of macroscopic clusters (>1 mm in size) in protoplanetary disks.Während der ersten Schritte der Bildung eines neuen Planetensystems klumpt und wächst Staub in der protoplanetaren Scheibe, die sich um einen neu-geformten Stern dreht. In dieser Scheibe führen Stöße zwischen Staubteilchen zu Teilchenwachstum. Staubaggregate wachsen bis ihre Größe und Relativgeschwindigkeiten hoch genug sind, dass Stöße zu Abprallen oder Fragmentierung führen. Das Suborbital Particle and Aggregation Experiment (SPACE) wurde entworfen und gebaut, um Stöße zwischen 100 µm-großen SiO2 Aggregate zu beobachten. Das Experiment wurde am Fallturm Bremen im August 2011 und auf der REXUS 12 Rakete im März 2012 durgeführt, wo die Schwerelosigkeitsbedingungen Teilchen-Relativgeschwindigkeiten unter 1 cm/s ermöglichten. Während der Experimente wurde die Bildung von Klumpen beobachtet, bestehend aus einer Vielzahl an Einzelaggregaten (mehr als 10^4), die bis zu einer Größe von 5 mm wuchsen. Die Ergebnisse der Datenanalyse zeigten, dass die Haftwahrscheinligkeit zwischen solchen Klumpen und zwischen Einzelteilchen und Klumpen viel höher ist als für Stöße zwischen zwei Einzelteilchen. Während des Raketenfluges konnte diese Haftwahrscheinligkeit während des Übergangs von Haftung zu Abprallen durchgehend gemessen werden. Es wurde auch gezeigt, dass die gebildeten Klumpen zerbrechlicher als Einzelteilchen sind und schon bei Stoßgeschwindigkeiten von 5 cm/s fragmentieren. Die Entwicklung der beobachteten Aggregatklumpen lieferte auch Informationen über ihre Stoß- und Kohäsionseigenschaften. Deren fraktale Dimension, Zugfestigkeit ihrer Komponenten und effektive Oberflächenenergie konnte gemessen werden. Zusätzlich wurden auch Kontakt Roll- und Bruchenergien Schwellwerte bestimmt. Diese verschiedenen Klumpen Eigenschaften sind wichtige Beiträge zu numerischen Simulationen, die Staubwachstum in protoplanetaren Scheiben berechnen

Regolith behavior under asteroid-level gravity conditions: low-velocity impact experiments

The dusty regolith covering the surfaces of asteroids and planetary satellites differs in size, shape, and composition from terrestrial soil particles and is subject to very different environmental conditions. Experimental studies of the response of planetary regolith in the relevant environmental conditions are thus necessary to facilitate future Solar System exploration activities. We combined the results and provided new data analysis elements for a series of impact experiments into simulated planetary regolith in low-gravity conditions using two experimental setups: the Physics of Regolith Impacts in Microgravity Experiment (PRIME) and the COLLisions Into Dust Experiment (COLLIDE). Results of these experimental campaigns found that there is a significant change in the regolith behavior with the gravity environment. In a 10-2g environment (Lunar g levels), only embedding of the impactor was observed and ejecta production was produced for most impacts at > 20 cm/s. Once at microgravity levels (<10-4g), the lowest impact energies also produced impactor rebound. In these microgravity conditions, ejecta started to be produced for impacts at > 10 cm/s. The measured ejecta speeds were lower than the ones measured at reduced-gravity levels, but the ejected masses were higher. The mean ejecta velocity shows a power-law dependence on the impact energy with an index of ~0.7. When projectile rebound occurred, we observed that its coefficients of restitution on the bed of regolith simulant decrease by a factor of 10 with increasing impact speeds from ~5 cm/s up to 100 cm/s. We could also observe an increased cohesion between the JSC-1 grains compared to the quartz sand targets

Asteroids Inside Out: Radar Tomography

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Assessing changes in global fire regimes

PAGES, Past Global Changes, is funded by the Swiss Academy of Sciences and the Chinese Academy of Sciences and supported in kind by the University of Bern, Switzerland. Financial support was provided by the U.S. National Science Foundation award numbers 1916565, EAR-2011439, and EAR-2012123. Additional support was provided by the Utah Department of Natural Resources Watershed Restoration Initiative. SSS was supported by Brigham Young University Graduate Studies. MS was supported by National Science Centre, Poland (grant no. 2018/31/B/ST10/02498 and 2021/41/B/ST10/00060). JCA was supported by the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No 101026211. PF contributed within the framework of the FCT-funded project no. UIDB/04033/2020. SGAF acknowledges support from Trond Mohn Stiftelse (TMS) and University of Bergen for the startup grant ‘TMS2022STG03’. JMP participation in this research was supported by the Forest Research Centre, a research unit funded by Fundação para a Ciência e a Tecnologia I.P. (FCT), Portugal (UIDB/00239/2020). A.-LD acknowledge PAGES, PICS CNRS 06484 project, CNRS-INSU, Région Nouvelle-Aquitaine, University of Bordeaux DRI and INQUA for workshop support.Background The global human footprint has fundamentally altered wildfire regimes, creating serious consequences for human health, biodiversity, and climate. However, it remains difficult to project how long-term interactions among land use, management, and climate change will affect fire behavior, representing a key knowledge gap for sustainable management. We used expert assessment to combine opinions about past and future fire regimes from 99 wildfire researchers. We asked for quantitative and qualitative assessments of the frequency, type, and implications of fire regime change from the beginning of the Holocene through the year 2300. Results Respondents indicated some direct human influence on wildfire since at least ~ 12,000 years BP, though natural climate variability remained the dominant driver of fire regime change until around 5,000 years BP, for most study regions. Responses suggested a ten-fold increase in the frequency of fire regime change during the last 250 years compared with the rest of the Holocene, corresponding first with the intensification and extensification of land use and later with anthropogenic climate change. Looking to the future, fire regimes were predicted to intensify, with increases in frequency, severity, and size in all biomes except grassland ecosystems. Fire regimes showed different climate sensitivities across biomes, but the likelihood of fire regime change increased with higher warming scenarios for all biomes. Biodiversity, carbon storage, and other ecosystem services were predicted to decrease for most biomes under higher emission scenarios. We present recommendations for adaptation and mitigation under emerging fire regimes, while recognizing that management options are constrained under higher emission scenarios. Conclusion The influence of humans on wildfire regimes has increased over the last two centuries. The perspective gained from past fires should be considered in land and fire management strategies, but novel fire behavior is likely given the unprecedented human disruption of plant communities, climate, and other factors. Future fire regimes are likely to degrade key ecosystem services, unless climate change is aggressively mitigated. Expert assessment complements empirical data and modeling, providing a broader perspective of fire science to inform decision making and future research priorities.Peer reviewe

Lunar Volatiles and Solar System Science

Understanding the origin and evolution of the lunar volatile system is not only compelling lunar science, but also fundamental Solar System science. This white paper (submitted to the US National Academies' Decadal Survey in Planetary Science and Astrobiology 2023-2032) summarizes recent advances in our understanding of lunar volatiles, identifies outstanding questions for the next decade, and discusses key steps required to address these questions

Du jeu dans la langue. Traduire le jeu de mots

International audienceTraduire peut être ludique, mais le ludique peut-il être traduit ? Pour le traductologue, l'enjeu suprême est offert par le jeu de mots : jeu sur et avec les mots (anagramme, calembour, contrepèterie, paronomase…), jeu sur le langage (création linguistique à visée humoristique : motvalise, détournement parodique…), voire jeu de mots involontaire dû aux accidents de langue. Cet ouvrage offre un panorama sur le sujet, utile aussi bien au traductologue qu’au comparatiste, au traducteur qu’à l’étudiant, à l’humoriste ou au simple curieux

Loose in translation: translating wordplay

International audienceTraduire peut être ludique, mais le ludique peut-il être traduit ? Pour le traductologue, l'enjeu suprême est offert par le jeu de mots : jeu sur et avec les mots (anagramme, calembour, contrepèterie, paronomase…), jeu sur le langage (création linguistique à visée humoristique : mot-valise, détournement parodique…), voire jeu de mots involontaire dû aux accidents de langue. Cet ouvrage offre un panorama sur le sujet, utile aussi bien au traductologue qu’au comparatiste, au traducteur qu’à l’étudiant, à l’humoriste ou au simple curieux. Car le jeu de mots amuse et engendre équivoque et paradoxe, brouille les frontières et joue de la provocation, pour procurer un plaisir de lecture ou de spectature en se prêtant aux expérimentations langagières. Face à ces contraintes fortes, les traducteurs se piquent au jeu en toutes langues et offrent solutions, recours, stratagèmes, analysés ici dans de nombreux champs d’application : littérature, théâtre, cinéma, séries audiovisuelles, presse..

Secret versus public reserve price in an “outcry” English procurement auction: Experimental results

International audienc