L’enregistrement tardiglaciaire de Dourges (Nord de la France, bassin de la Deûle) : évolution d’une zone lacustre et gisements archéologiques associés

Une dépression dans le fond de la vallée de la Deûle, au pied du versant crayeux de la Gohelle (bassin minier de Lens), a permis la mise en place et la conservation de sédiments tardiglaciaires lacustres et palustres avec des sites paléontologiques et archéologiques associés. La nature des dépôts est commandée par les variations d’humidité. Un épisode lacustre est daté du Bølling. Il est caractérisé par le développement d’une biocénose aquatique (poissons et mollusques). Un fragment de harpon magdalénien et les restes d’un aurochs de grande taille ont été trouvés dans le tuf lacustre. Le Dryas moyen se distingue par un assèchement et un hiatus stratigraphique. Après une nouvelle période d’hydrologie plus marquée (récurrence de crues de courte durée), la zone redevient marécageuse à l’Allerød. Elle est fréquentée par des chasseurs Federmesser ainsi qu’en témoigne une halte de chasse qui a livré des éléments fugaces mais caractéristiques : sagaie, pointe en os barbelée, pointe de flèche. La fin de l’Allerød se caractérise par un retour à des conditions sèches et la formation d’un sol humifère. Le refroidissement du Dryas récent engendre une déstabilisation du versant et le début du comblement de la dépression par des colluvions limoneuses. Leur base a livré un crâne d’élan.A dipped area in the bottom of the Deûle valley, bottom the chalky slope of the Gohelle country (Lens mining basin), has yielded Late Glacial deposits with palaeontological remains and archaeological artifacts. The nature of the deposits appears linked to humidity variations. A lacustrine episode dated from the Bølling is characterized by the development of an aquatic biocoenosis (fish and mollusks). A fragment of a Magdalenian harpoon and the remains of a large wild ox were discovered in the lacustrine tufa. The Older Dryas corresponds to dry conditions and a stratigraphic hiatus. After a new increase in hydrological conditions (short floodings), the area turns marshy again during the Allerød. Federmesser hunters are represented by assegai, barbed bone points and arrow points. The end of the Allerød corresponds to a return to dry conditions and the formation of humic soil. During the Younger Dryas the cooling provokes slope erosion and the filling up of the hollow by silt colluvium. An elk skull was discovered at the base of this last deposit

Magnetour: Surfing Planetary Systems on Electromagnetic and Multi-Body Gravity Fields

In this NIAC Phase One study, we propose a new mission concept, named Magnetour, to facilitate the exploration of outer planet systems and address both power and propulsion challenges. Our approach would enable a single spacecraft to orbit and travel between multiple moons of an outer planet, with no propellant required. Our approach would enable a single spacecraft to orbit and travel between multiple moons of an outer planet, with no propellant nor onboard power source required. To achieve this free-lunch _Grand Tour', we exploit the unexplored combination of magnetic and multi-body gravitational fields of planetary systems, with a unique focus on using a bare tether for power and propulsion. The main objective of the study is to develop this conceptually novel mission architecture, explore its design space, and investigate its feasibility and applicability to enhance the exploration of planetary systems within a 10-year timeframe. Propellantless propulsion technology offers enormous potential to transform the way NASA conducts outer planet missions. We hope to demonstrate that our free-lunch tour concept can replace heavy, costly, traditional chemical-based missions and can open up a new variety of trajectories around outer planets. Leveraging the powerful magnetic and multi-body gravity fields of planetary systems to travel freely among planetary moons would allow for long-term missions and provide unique scientific capabilities and flagship-class science for a fraction of the mass and cost of traditional concepts. New mission design techniques are needed to fully exploit the potential of this new concept.This final report contains the results and findings of the Phase One study, and is organized as follows. First, an overview of the Magnetour mission concept is presented. Then, the research methodology adopted for this Phase One study is described, followed by a brief outline of the main findings and their correspondence with the original Phase One task plan. Next, an overview of the environment of outer planets is provided, including magnetosphere, radiation belt and planetary moons. Then performance of electrodynamic tethers is assessed, as well as other electromagnetic systems. A method to exploit multi-body dynamics is given next. These analyses allow us to carry out a Jovian mission design to gain insight in the benefits of Magnetour. In addition, a spacecraft configuration is presented that fully incorporates the tether in the design. Finally technology roadmap considerations are discussed

Potential Cislunar and Interplanetary Proving Ground Excursion Trajectory Concepts

NASA has been investigating potential translunar excursion concepts to take place in the 2020s that would be used to test and demonstrate long duration life support and other systems needed for eventual Mars missions in the 2030s. These potential trajectory concepts could be conducted in the proving ground, a region of cislunar and near-Earth interplanetary space where international space agencies could cooperate to develop the technologies needed for interplanetary spaceflight. Enabled by high power Solar Electric Propulsion (SEP) technologies, the excursion trajectory concepts studied are grouped into three classes of increasing distance from the Earth and increasing technical difficulty: the first class of excursion trajectory concepts would represent a 90-120 day round trip trajectory with abort to Earth options throughout the entire length, the second class would be a 180-210 day round trip trajectory with periods in which aborts would not be available, and the third would be a 300-400 day round trip trajectory without aborts for most of the length of the trip. This paper provides a top-level summary of the trajectory and mission design of representative example missions of these three classes of excursion trajectory concepts

NASA Planetary Mission Concept Study: Assessing: Dwarf Planet Ceres' past and Present Habitability Potential

The Dawn mission revolutionized our understanding of Ceres during the same decade that has also witnessed the rise of ocean worlds as a research and exploration focus. We will report progress on the Planetary Mission Concept Study (PMCS) on the future exploration of Ceres under the New Frontiers or Flagship program that was selected for NASA funding in October 2019. At the time this writing, the study was just kicked off, hence this abstract reports the study plan as presented in the proposal

Overview of the Mission Design Reference Trajectory for NASA's Asteroid Redirect Robotic Mission

The National Aeronautics and Space Administration's (NASA's) recently cancelled Asteroid Redirect Mission was proposed to rendezvous with and characterize a 100 m plus class near-Earth asteroid and provide the capability to capture and retrieve a boulder off of the surface of the asteroid and bring the asteroidal material back to cislunar space. Leveraging the best of NASA's science, technology, and human exploration efforts, this mission was originally conceived to support observation campaigns, advanced solar electric propulsion, and NASA's Space Launch System heavy-lift rocket and Orion crew vehicle. The asteroid characterization and capture portion of ARM was referred to as the Asteroid Redirect Robotic Mission (ARRM) and was focused on the robotic capture and then redirection of an asteroidal boulder mass from the reference target, asteroid 2008 EV5, into an orbit near the Moon, referred to as a Near Rectilinear Halo Orbit where astronauts would visit and study it. The purpose of this paper is to document the final reference trajectory of ARRM and the challenges and unique methods employed in the trajectory design of the mission

Influence of fast interstellar gas flow on dynamics of dust grains

The orbital evolution of a dust particle under the action of a fast interstellar gas flow is investigated. The secular time derivatives of Keplerian orbital elements and the radial, transversal, and normal components of the gas flow velocity vector at the pericentre of the particle's orbit are derived. The secular time derivatives of the semi-major axis, eccentricity, and of the radial, transversal, and normal components of the gas flow velocity vector at the pericentre of the particle's orbit constitute a system of equations that determines the evolution of the particle's orbit in space with respect to the gas flow velocity vector. This system of differential equations can be easily solved analytically. From the solution of the system we found the evolution of the Keplerian orbital elements in the special case when the orbital elements are determined with respect to a plane perpendicular to the gas flow velocity vector. Transformation of the Keplerian orbital elements determined for this special case into orbital elements determined with respect to an arbitrary oriented plane is presented. The orbital elements of the dust particle change periodically with a constant oscillation period or remain constant. Planar, perpendicular and stationary solutions are discussed. The applicability of this solution in the Solar system is also investigated. We consider icy particles with radii from 1 to 10 micrometers. The presented solution is valid for these particles in orbits with semi-major axes from 200 to 3000 AU and eccentricities smaller than 0.8, approximately. The oscillation periods for these orbits range from 10^5 to 2 x 10^6 years, approximately.Comment: 22 pages, 3 figures; Accepted for publication in Celestial Mechanics and Dynamical Astronom

Light Variability Illuminates Niche-Partitioning among Marine Picocyanobacteria

Prochlorococcus and Synechococcus picocyanobacteria are dominant contributors to marine primary production over large areas of the ocean. Phytoplankton cells are entrained in the water column and are thus often exposed to rapid changes in irradiance within the upper mixed layer of the ocean. An upward fluctuation in irradiance can result in photosystem II photoinactivation exceeding counteracting repair rates through protein turnover, thereby leading to net photoinhibition of primary productivity, and potentially cell death. Here we show that the effective cross-section for photosystem II photoinactivation is conserved across the picocyanobacteria, but that their photosystem II repair capacity and protein-specific photosystem II light capture are negatively correlated and vary widely across the strains. The differences in repair rate correspond to the light and nutrient conditions that characterize the site of origin of the Prochlorococcus and Synechococcus isolates, and determine the upward fluctuation in irradiance they can tolerate, indicating that photoinhibition due to transient high-light exposure influences their distribution in the ocean

A Systematic Concept Exploration Methodology Applied to Venus In Situ Explorer

This presentation was part of the session : Probe Missions to the Giant Planets, Titan and VenusSixth International Planetary Probe WorkshopA critical task in any design process is the initial conversion of customer or program objectives into a baseline system architecture. This task becomes particularly important for space exploration systems that have unique requirements which, in many cases, have never been met before. A useful tool to the space systems engineer would be a methodology which helps to make this objectives-to-design conversion more systematic and efficient. Presented in this paper is such a methodology frequently used at the Georgia Institute of Technology, and in this paper the methodology is applied to initial concept formulation for the Venus In Situ Explorer (VISE) mission. VISE is one of six New-Frontiers-class missions to occur within the next 30 years that NASA addresses in its Solar System Exploration Roadmap. VISE is envisioned as an aerial mission that will study Venus' atmospheric composition as well as descend briefly to the surface to acquire samples for later analysis at more benign altitudes. Common to both VISE and its successor, Venus Mobile Explorer, is the challenge to operate under the extreme temperatures (about 730 K) and pressures (about 90 atm) present at the Venusian surface. In order to establish a baseline mission and vehicle concept for VISE, the methodology presented here begins with problem definition and the generation of functional and operational architectures. Customer requirements and engineering targets are set through an established set of tools known as the seven management and planning tools and through the use of a quality function deployment (QFD). A morphological matrix is used to identify 12.4 billion potential solutions in the concept space. From this concept space, six representative designs are chosen to demonstrate how alternatives from the morphological matrix may be ranked through multi-attribute decision making (MADM) techniques such as the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) and Pugh concept selection matrices. Two of the six concepts are eliminated based on these MADM techniques, and the remaining four concepts are recognized as requiring more in-depth study to allow definitive rankings to be assigned. A notional modeling and simulation framework for this problem is formed which could be used to complete such an in-depth, quantitative study. This paper principally serves to illustrate an example of how a systematic objectives definition, concept generation, and downselection methodology can be applied to advanced interplanetary missions (specifically in the example of Venus In Situ Explorer). The methodology and tools presented here are shown as a helpful guide and addition to the toolbox of the space systems engineer during the advanced planning stages of design.Georgia Institute of Technology ; National Institute of Aerospac