Axel Hagermann

As the Moon lacks a collisional atmosphere, the space plasmas and the solar radiation can directly interact with its rocky surface, causing significant surface charging. Lunar surface charging and its resultant surface dust environment impact the safety and functionality of human and technology systems on the lunar surface. Therefore, to characterize the surface electric field configuration is important for the lunar exploration activities. The electromagnetic field configuration on the lunar surface is rather poorly known and will be studied on this project through computational modeling using Simion.The Lunar Boomerang project aims to launch charged particles from the lunar surface and probe the electromagnetic field configurations using the properties of returning particles. In addition to the electric force, charged particles affected by the magnetic force are prone to gyrate with gyro-radii reaching up to several km. Depending on the particle energy, emission direction, and distribution of the field, a fraction of particles will return. A particle detector on the same instrument will detect these returning particles. From these, an electromagnetic field configuration can be determined.This is an innovative technique where IRF, the Swedish Institute for Space Physics will conduct proof-of-concept studies. We carry out numerical simulations using the particle tracing software, SIMION, to trace charged particle motion in a predefined electromagnetic field, and records all the information of the particles hitting a surface. By varying electromagnetic fields and initial particle energies and direction to predict the characteristics of these returning particles. The results of simulations with different electromagnetic field configurations will be presented and discussed.

The Ceres Autonomous Lander Into Crater Occator (CALICO) was proposed in response to ESA’s M7-call for future space missions. CALICO is a mission to study the surface and interior of dwarf planet Ceres, the closest ocean world to Earth. Ceres’ accessible location in the main belt makes it a compelling target for exploration since it was classified as an ocean world in the wake of NASA’s Dawn mission, which provided a wealth of data. DAWN also left open many questions, such as whether the interior of Ceres ever had the potential for habitability.CALICO’s space segment consists of two components: the CALICO surface element is to land in Occator crater to analyse the salt- and organic-rich deposits of Vinalia Faculae, where building blocks of life might be accessible on the surface. The CALICO orbital element will characterize Ceres’ magnetic and particle environment to establish the presence of subsurface volatile reservoirs.We present an overview of CALICO’s science objectives, instrument payload and a possible mission scenario. Although not selected to go forward into Phase A, CALICO - or any CALICO-like mission - has great potential to answer such fundamental questions about our place in the Solar System. The CALICO consortium will continue its efforts to realize a mission to Ceres.

Snow ice (SI) forms from freezing wet snow, known as slush, and contributes to the thickness of level and brash ice. However, the mechanism of snow-slush-snow ice transformation has not been extensively investigated to date, despite the difference in the freezing rate of slush in comparison with water is important for estimating the ice thickness. In this study, we examined the growth of initial congelation ice (CI) and snow ice (SI) in a fresh water tank exposed to outdoor weather conditions in Luleå, northern Sweden. The tank of size 1.8 × 0.65 × 1.2 m in length, width and height was divided into two compartments to facilitate the simultaneous growth of CI and SI. A total of 12 experiments were conducted in the years 2021 and 2022. The transformation from slush to snow ice was achieved by submerging various amounts of snow in the compartments. It was observed that approximately 35% of the initial snow transformed into SI. Snow ice grew 4 mm°C^−0.5 d^−0.5 faster than congelation ice. The CI growth under SI was 1 mm°C^−0.5 d^−0.5 slower than the CI growth under CI. This study provides valuable insights for modelling snow-slush-snow ice transformation and designing future laboratory-scale experiments.

In this abstract we discuss a proposal for a microgravity flight campaign within which we will investigate penetrometry in a microgravity environment. Understanding the mechanical properties of solar system minor bodies is essential for understanding their origin and evolution. Past missions such as Hayabusa-2 and OSIRIS-REX have landed on asteroids and taken samples to discover what these bodies are made of. However, there has been conflicting evidence and reports into the physical properties of the granular surface material of these bodies. With future missions such as JAXA’s MMX mission travelling to Phobos to take a sample of the body the results from this campaign will be very important to that and future missions. Penetrometry, i.e. the determination of the reaction force an object experiences as it penetrates into a surface, can help to understand the essential properties regarding regolith such as grain size, grain shape, cohesion and bulk density. The usage of penetrometry however has mostly been limited ground-based studies such as soil sciences or even cheese maturation. Very little is known about the underlying physics of penetrometry. Results of penetrometry experiments are largely analysed based on empirical models, which presents us with a challenge if we want to apply the same parameters to understand granular materials on asteroid surfaces. Obviously, gravity cannot be eliminated in the laboratory. Hence, it is essential to verify penetrometry as a method and validate penetrometry instrument designs in microgravity.For this purpose, we propose a parabolic flight campaign. Our experiment will test the use of penetrometry in asteroid-analogue environments by investigating samples with varying properties such as grain size and shape. The microgravity aspect of the experiment is one of the most important factors because it enables us to correlate laboratory experiments at 1g with identical setups in a gravity regime relevant to asteroids. The proposed experimental setup will include a variety of samples with varying grain sizes, grain shapes, porosities and grain size distributions. The penetrometer used will also have varying properties such as the diameter, shape, and velocity of penetration. A robotic arm will push a penetrometer into the samples to measure the reaction force which can then be used to determine the mechanical properties of the samples. By varying the samples and penetrometer properties it will be possible to better understand the relevant parameters affecting reaction force. The suitability of the setup will also be reviewed to understand its usage and applicability in microgravity environments such as the robotic arm that will be used. All of the experiments carried out during the parabolic campaign will also be done at 1g to compare the tests in varying gravity levels. With a better understanding of the science behind penetrometry and the effects of microgravity, future missions will be better prepared and be able to use penetrometry more effectively to understand small-body surfaces.

The surfaces of all solid bodies in the solar system, planets, moons, comets and asteroids, experience short-term temporal variations of solar irradiation which depend on their respective spin rates. These so-called insolation cycles affect temperature variations, climate, photosynthesis in plants, etc. Hence, experimental reproduction of these cycles is important for space analogue simulations. In this short note we describe a simple, low-cost method to simulate diurnal cycles in the laboratory using a type of commercial solar simulator commonly used for experimental investigation in planetary science.

CoPhyLabLaboratory experiments are of major importance to understand the activity of comets and to support future space missions. However, past comet simulation experiments were performed under the assumption that comets are mainly composed of water ice with only a limited amount of dust. In the past years, however, the Rosetta mission has shown that cometary nuclei consist primarily of dust and less volatile materials are present than previously thought. Hence, it is high time to set up a new series of laboratory experiments with the aim to investigate the physics of realistic cometary analogue materials. This task is currently addressed by the CoPhyLab (Comet Physics Laboratory) which is a joint project among different partner institutions. This laboratory aims at studying the physics of cometary analogue materials. This task is approached by firstinvestigating isolated physical properties in so-called small experiments (S experiments). In a next step, the experiment’s complexity is increased step-by-step by either adding further components to the sample, or by studying several physical properties under different conditions (large experiments, which will be performed in the L chamber).  S1: the tensile strength of organic materialsThe knowledge of the tensile strength of the cometary surface is of key importance to better understand the activity of comets. The tensile strength determines the strain required to detach material from the surface. As organic materials are ubiquitous in space, they could have played an important role during the planet formation process and are most likely incorporated into cometary nuclei. This S experiment campaign provides new measurements on the tensile strength of various granular organic materials. These materials are investigated by the Brazilian Disc Test and the measured values are normalised to a grain size of one micrometer and a volume filling factor of 0.5 for better comparability. The experiments show that the tensile strength of organic materials ranges over four orders of magnitude. Graphite and paraffin have much higher tensile strengths values compared to silica, whereas the tensile strength of coals is very low. This work demonstrates that organic materials are not generally stickier than silicates, or water ice. S2: gas permeability of analogue materials  The cometary nucleus is made of water ice, organics and silicateous dust and the ice is trapped inside the matrix of non-volatiles. Hence, the evolving gas has to stream away from its originating region inside the surface layers towards the surface. This work package has the aim to investigate the gas transport mechanisms through porous cometary analogue materials. Therefore, gas flow measurements are performed to investigate the permeability of several materials, which are chosen to mimic cometary surface properties. With these measurements, the gas permeability and the Knudsen diffusion coefficient of the sample materials are obtained. These simulants are tested with respect to different filling heights, packing properties and grain shapes. The gas flow experiments show that the grain size distribution and the packing density of the samples are primarily influencing the permeability of the sample.  S3: thermal conductivity of analogue materialsMeasurements of the thermal properties of analogue materials are essential in interpreting remote sensing data and the findings of in-situ instruments. The thermal properties of the subsurface layers determine the surface temperature of asteroids and comets. The temperature stratification inside planetary object is a key parameter to understand the processing of their interior. This experiment campaign is dedicated to measure the thermal properties of analogue materials. In preparation for these measurements we have set up a small vacuum chamber equipped with an infrared camera and temperature sensors. The samples are illuminated for a short duration by a laser. We then compare the measured temperature profiles with the predictions of a thermophysical model to determine the thermal conductivity of the samples. S4: ejection of materialWhen comets approach the Sun, the sublimation pressure will be reached inside the material. If the tensile strength is exceeded by the evolving pressure, the particles can be ejected from the cometary surface and are accelerated. However, the details of the dust dynamics close to the surface are not understood in detail. The idea of this S experiment campaign is to develop an experimental routine to track ejected particles from a sample composed of granular water ice. Therefore, we recorded the power of the illumination, the temperature of the sample and measured the particle trajectories with an high speed camera. Furthermore, the experiments are also simulated by a thermophysical model. Our experiments show that samples composed of pure granular water ice can eject water-ice particles by the pressure build up of water vapour in their interior. Compressed samples posses an higher activity level (ejection events per second) compared to uncompressed samples. The ejected particles have a non-zero initial velocity which is most probably caused by a very fast acceleration of the particles before the first data point is recorded by the camera. The L chamberThe core of this project is the realisation of a comet simulation chamber which will be capable to utilise multiple instruments to monitor and measure the sample properties before, during and after the experiment campaigns. This chamber will be used to perform long duration experiments at low temperatures and low pressures. At this stage (end of June, 2020), the chamber is already installed in place and is vacuum tight, the cooling shield is assembled and the sample carrier cart as well as the self-made glove box are ready to use. The next steps comprise the integration of the cooling shield and the main cooling system. We foresee to run...