The water processes that affect the upper layers of the surface of Mars are not yet fully understood. Describing the processes that may induce changes in the water content ofthe surface is critical to determine the present-day habitability of the Martian surface,understand the atmospheric water cycle, and estimate the efficiency of future water extraction procedures from the regolith for In-Situ-Resource-Utilization (ISRU). This PhD thesis describes the design, development, and plausible uses of a Martian environmental facility ‘SpaceQ chamber’ which allows to simulate the near surface water cycle.

This facility has been specifically designed to investigate the effect of water on the Martian surface. SpaceQ has been used to investigate the material curation and has demonstrated that the regolith, when mixed with super absorbent polymer (SAP), water, and binders exposed to Martian conditions, can form a solid block, and retain more than 80% of the added water, which may be of interest to screen radiation while maintaining a low weight. The thesis also includes the testing of HABIT operation, of theESA/IKI ExoMars 2022 robotic mission to Mars, within the SpaceQ chamber, underMartian conditions similar to those expected at Oxia Planum. The tests monitor the performance of the brine compartment, when deliquescent salts are exposed to atmospheric water.

In this thesis, a computational model of the SpaceQ using COMSOL Multiphysics has been implemented to study the thermal gradients and the near surface water cycle under Martian temperature and pressure experimental conditions. The model shows good agreement with experiments on the thermal equilibration time scales and gradients. The model is used to extrapolate the one-point relative humidity measurement of the experimental to each grid points in the simulation. This gives an understanding ofthe gradient in atmospheric water relative humidity to which the experimental samples such as deliquescent salts and Martian regolith simulants are exposed at different time intervals. The comparison of the thermal simulation and the experimental behavior of HABIT instrument tests, shows an extra internal heating source of about 1 W which can be attributed to the hydration and deliquescence of the salts exposed to Martian conditions when in contact with atmospheric moisture.

Finally, this thesis experimentally demonstrates that pure liquid water can persist for 3.5 to 4.5 hours at Mars surface conditions. The simulated ground captured 53% of the atmospheric water either as pure liquid water, hydrate, or brine. The result concludes  that the relative humidity values at night-time on Mars may allow for significant water absorption by the ground, which is released at sunrise. The water cycle dynamics near the surface is therefore always out of equilibrium. After frost formation, thin films of water may survive for a few hours. The results of this thesis about the water cycle on Mars, and about the interaction of atmospheric water with regolith and salts, have implications for the present-day habitability of the Martian surface and planetary protection policies.

Environmental chambers are used to test the expected performance of space instrumentation and to investigate certain processes which are relevant in space or other planetary environments. In this study, a computational model of an existing Martian experimental facility is investigated numerically using COMSOL Multiphysics. For this purpose, we simulate the near surface water cycle under Martian temperature and pressure experimental conditions as tested inside the chamber and we compare the simulations with the experimental data. The model shows good agreement with experiments on the equilibration time scales and thermal gradients. Due to the imposibility to place sensors at multiple locations inside the chamber, we use the model to extrapolate the one-point relative humidity of the experimental data to each grid points in the simulation. This model gives an understanding of the gradient in atmospheric water relative humidity to which the experimental samples such as deliquescent salts and Martian regolith simulants are exposed at different time intervals. The of the performance of HABIT instrument during the tests, of the ESA/IKI ExoMars 2022 robotic mission to Mars, when compared with the model shows the existence of an extra internal heating source of about 1 W which can be attributed to the hydration and deliquescence of the salts exposed to Martian conditions when in contact with atmospheric moisture. In addition, the presented model is used to predict the thermal gradients and understand the time response when the chamber is heated in vacuum conditions. Our analysis shows that for thermal vacuum tests, the chamber will take about 2.5 h to reach the test temperature of 420 K.

Tribocorrosion is a degradation phenomenon of material surfaces subjected to the combined action of mechanical loading and corrosion attack caused by the environment. Although corrosive chemical species such as materials like chloride atoms, chlorides, and perchlorates have been detected on the Martian surface, there is a lack of studies of its impact on materials for landed spacecraft and structures that will support surface operations on Mars. Here, we present a series of experiments on the stainless-steel material of the ExoMars 2020 Rosalind Franklin rover wheels. We show how tribocorrosion induced by brines accelerates wear on the materials of the wheels. Our results do not compromise the nominal ExoMars mission but have implications for future long-term surface operations in support of future human exploration or extended robotic missions on Mars.

The water content of the upper layers of the surface of Mars is not yet quantified. Laboratory simulations are the only feasible way to investigate this in a controlled way on Earth, and then compare it with remote and in situ observations of spacecrafts on Mars. Describing the processes that may induce changes in the water content of the surface is critical to determine the present-day habitability of the Martian surface, to understand the atmospheric water cycle, and to estimate the efficiency of future water extraction procedures from the regolith for In Situ Resource Utilization (ISRU). This paper illustrates the application of the SpaceQ facility to simulate the near-surface water cycle under Martian conditions. Rover Environmental Monitoring Station (REMS) observations at Gale crater show a non-equilibrium situation in the atmospheric H₂O volume mixing ratio (VMR) at night-time, and there is a decrease in the atmospheric water content by up to 15 g/m² within a few hours. This reduction suggests that the ground may act at night as a cold sink scavenging atmospheric water. Here, we use an experimental approach to investigate the thermodynamic and kinetics of water exchange between the atmosphere, a non-porous surface (LN₂-chilled metal), various salts, Martian regolith simulant, and mixtures of salts and simulant within an environment which is close to saturation. We have conducted three experiments: the stability of pure liquid water around the vicinity of the triple point is studied in experiment 1, as well as observing the interchange of water between the atmosphere and the salts when the surface is saturated; in experiment 2, the salts were mixed with Mojave Martian Simulant (MMS) to observe changes in the texture of the regolith caused by the interaction with hydrates and liquid brines, and to quantify the potential of the Martian regolith to absorb and retain water; and experiment 3 investigates the evaporation of pure liquid water away from the triple point temperature when both the air and ground are at the same temperature and the relative humidity is near saturation. We show experimentally that frost can form spontaneously on a surface when saturation is reached and that, when the temperature is above 273.15 K (0 °C), this frost can transform into liquid water, which can persist for up to 3.5 to 4.5 h at Martian surface conditions. For comparison, we study the behavior of certain deliquescent salts that exist on the Martian surface, which can increase their mass between 32% and 85% by absorption of atmospheric water within a few hours. A mixture of these salts in a 10% concentration with simulant produces an aggregated granular structure with a water gain of approximately 18- to 50-wt%. Up to 53% of the atmospheric water was captured by the simulated ground, as pure liquid water, hydrate, or brine.

This paper describes a protocol to design experiments to study the formation of brines under Martian conditions and monitor the process with electrical conductivity measurements. We used the Engineering Qualification Model (EQM) of Habitability: Brines, Irradiation, and Temperature (HABIT)/ExoMars 2022 instrument for the experiment setup but we provide a brief account of constructing a simple and inexpensive electrical conductivity measurement setup. The protocol serves to calibrate the electrical conductivity measurements of the salt deliquescence into brine in a simulated Martian environment. The Martian conditions of temperature (-70 °C to 20 °C), relative humidity (0% to 100%) and pressure (7 - 8 mbar) with carbon-dioxide atmosphere were simulated in the SpaceQ Mars simulation chamber, a facility at the Luleå University of Technology, Sweden. The hydrate form of the known amount of salt accommodated between a pair of electrodes and thus the electrical conductivity measured depends predominantly on its water content and the temperature and relative humidity of the system. Electrical conductivity measurements were carried out at 1 Hz while exposing salts to a continuously increasing relative humidity (to force transitioning through various hydrates) at different Martian temperatures. For demonstration, a day-night cycle at Oxia Planum, Mars (the landing site of ExoMars 2022 mission) was recreated.

PACKMAN (PArticle Counter k-index Magnetic ANomaly) is an autonomous, light and robust space weather instrument for operation within the subsurface, surface and atmosphere (as payload in stratospheric balloons) of the Earth. It has been designed using Commercial Off-The-Shelf (COTS) components to reduce the cost of each unit and to allow to have multiple units monitoring simultaneously at different sites and also incorporate an open-access citizen science approach. The hardware-core of each PACKMAN units, weights around 600 g and consumes about 500 mA of current at 12 V. PACKMAN has been deployed at multiple latitudes and altitudes ranging from stratospheric heights (corroborating its TRL8 maturity) to subsurface depths of around 1 km. The data from PACKMAN have been compared with the state-of-the-art ground-based observatories, and satellites and scientific observations have been documented. A 3-D network of PACKMAN units operating continuously around the globe, from the subsurface to the stratosphere, would help to improve the understanding of the space weather phenomena, and its implications on the climate and infrastructures. PACKMAN is also an excellent tool for education and outreach. This article outlines the building instructions of two types of PACKMAN units: PACKMAN-S for ground-based measurements and PACKMAN-B for stratospheric measurements aboard high-altitude balloons.

Geomorphological studies of the hidden and protected subsurface environments are crucial to obtain a greater insight into the evolution of planetary landforms, hydrology, climate, geology and mineralogy. From an astrobiological point of view subsurface environments are of interest for their potential habitability as they are local environments that are partially or fully shielded from the high levels of space and solar radiation. Furthermore, in the case of Mars, there is an increasing interest in searching for the presence of past or extant life in its subsurface. These applications make it mandatory to investigate equipment and instrumentation that allow for the study of subsurface geomorphology, as well as organic chemical biomarkers, such as biomolecules, carbon, nitrogen and sulphur isotopes, and other biologically significant minerals and gases. Mines on Earth can be used as analogues to investigate the geomorphology of Martian subsurface environments and perform astrobiology studies. With that goal, we have developed a low-cost, robust, remotely operable subsurface rover called KORE (KOmpact Rover for Exploration). This work illustrates the studies of a terrestrial analogue for the exploration of Mars using KORE during the Mine Analogue Research 6 (MINAR 6) campaign with the low-cost 3D mapping technology InXSpace 3D (In situ 3D mapping tool eXploration of space 3D). InXSpace 3D utilizes an RGB-D camera that captures depth information in addition to the RGB data of an image, operating based on the structured light principle capable of providing depth information in mm scale resolution at sub 3 m mapping range. InXSpace 3D is used to capture point clouds of natural and artificial features, thereby obtaining information about geologically relevant structures and also to incorporate them in earth mining safety. We tested two of the dense simultaneous localization and mapping (SLAM) algorithms: Kintinuous and Real-Time Appearance-Based Mapping (RTAB-Map) to check the performance of InXSpace 3D in a dark mine environment. Also, the air accumulation of volatiles such as methane and formaldehyde due to thermogenic and mining process was measured with the environmental station payload on the rover platform, which caters to both astrobiological significance and mine safety. The main conclusions of this work are: (1) a comparison made between the RTAB-Map algorithm and Kintinuous algorithm showed the superiority of Kintinuous algorithm in providing better 3D reconstruction; although RTAB-Map algorithm captured more points than the Kintinuous algorithm in the dark mine environment; (2) a comparison of point cloud images captured with and without lighting conditions had a negligible effect on the surface density of the point clouds; (3) close-range imaging of the polygonal features occurring on the halite walls using InXSpace 3D provided mm-scale resolution to enable further characterization; (4) heuristic algorithms to quickly post-process the 3D point cloud data provided encouraging results for preliminary analyses; (5) we successfully demonstrated the application of KORE to mine safety; and (6) the multi-sensors platform on KORE successfully monitored the accumulated volatiles in the mine atmosphere during its operation. The findings obtained during this KORE campaign could be incorporated in designing and planning future subsurface rover explorations to potential planetary bodies such as Mars with synergistic applications to subsurface environments in mines on Earth.

The HabitAbility: Brines, Irradiation and Temperature (HABIT) instrument will be part of the ExoMars 2020 mission (ESA/Roscosmos) and will be the first European In-situ Resource Utilization (ISRU) instrument capable of producing liquid water on Mars. HABIT is composed by two modules: Environmental Package (EnvPack) and Brine Observation Transition To Liquid Experiment (BOTTLE). EnvPack will help to study the current habitability conditions on Mars investigating the air and surface thermal ranges and Ultraviolet (UV) irradiance; and BOTTLE is a container with four independent vessels housing deliquescent salts, which are known to be present on Mars, where the liquid water will be produced after deliquescence. In order to prevent capillarity of deliquescent or hydrated salts, a mixture of deliquescent salts with Super Absorbent Polymer (SAP) based on polyacrylamide is utilized. This mixture has deliquescent and hydrogel properties and can be reused by applying a thermal cycle, complying thus with the purpose of the instrument. A High Efficiency Particulate Air (HEPA) grade filter made of polytetrafluroethylene (PTFE) porous membrane sandwiched between spunbounded non-woven fabric stands as a physical barrier allowing interaction between the gaseous molecules of the Martian atmosphere and the salt mixtures, and at the same time preventing the passage of any potential biological contamination from the cells to the outside or vice-versa. In addition to the physical barrier, a strict bioburden reduction and analysis procedure is applied to the hardware and the contained salt mixtures adhering to the European Cooperation for Space Standardization protocol of microbial examination of flight hardware (ECSS-Q-ST-70-55C). The deliquescent salts and the SAP products need to be properly treated independently to adhere to the planetary protection protocols. In this manuscript, we describe the bioburden reduction process utilized to sterilize the salt mixtures in BOTTLE and the assays adopted to validate the sterilization. We also describe the construction of a low-cost, portable ISO 7 cleanroom tent, exclusively designed for planetary protection tests. The sterilization process involves Dry Heat Microbial Reduction (DHMR) of the deliquescent salts and the SAP mixtures. The performance of SAP after DHMR is validated to ensure its working efficiency after sterilization. A slightly modified version of the standard swab assay is used in the validation process and a comparison is made between samples exposed to a thermal shock treatment and those without thermal shock, to determine the best assay to be applied for future space hardware utilizing such salt mixtures for planetary investigation and In-Situ Resource Utilization (ISRU). The demonstration of the compatibility of these products with the processes commonly required for space applications has implications for the future exploration of Mars.

We describe a versatile simulation chamber that operates under representative space conditions (pressures from < 10⁻⁵ mbar to ambient and temperatures from 163 to 423 K), the SpaceQ chamber. This chamber allows to test instrumentation, procedures, and materials and evaluate their performance when exposed to outgassing, thermal vacuum, low temperatures, baking, dry heat microbial reduction (DHMR) sterilization protocols, and water. The SpaceQ is a cubical stainless-steel chamber of 27,000 cm³ with a door of aluminum. The chamber has a table which can be cooled using liquid nitrogen. The chamber walls can be heated (for outgassing, thermal vacuum, or dry heat applications) using an outer jacket. The chamber walls include two viewports and 12 utility ports (KF, CF, and Swagelok connectors). It has sensors for temperature, relative humidity, and pressure, a UV–VIS–NIR spectrometer, a UV irradiation lamp that operates within the chamber as well as a stainless-steel syringe for water vapor injection, and USB, DB-25 ports to read the data from the instruments while being tested inside. This facility has been specifically designed for investigating the effect of water on the Martian surface. The core novelties of this chamber are: (1) its ability to simulate the Martian near-surface water cycle by injecting water multiple times into the chamber through a syringe which allows to control and monitor precisely the initial relative humidity inside with a sensor that can operate from vacuum to Martian pressures and (2) the availability of a high-intensity UV lamp, operating from vacuum to Martian pressures, within the chamber, which can be used to test material curation, the role of the production of atmospheric radicals, and the degradation of certain products like polymers and organics. For illustration, here we present some applications of the SpaceQ chamber at simulated Martian conditions with and without atmospheric water to (i) calibrate the ground temperature sensor of the Engineering Qualification Model of HABIT (HabitAbility: Brines, Irradiation and Temperature) instrument, which is a part of ExoMars 2022 mission. These tests demonstrate that the overall accuracy of the temperature retrieval at a temperature between −50 and 10 °C is within 1.3 °C and (ii) investigate the curation of composite materials of Martian soil simulant and binders, with added water, under Martian surface conditions under dry and humid conditions. Our studies have demonstrated that the regolith, when mixed with super absorbent polymer (SAP), water, and binders exposed to Martian conditions, can form a solid block and retain more than 80% of the added water, which may be of interest to screen radiation while maintaining a low weight. 

Autonomous exploration requires the use of movable platforms that carry a payload of instruments with a certain level of autonomy and communication with the operators. This is particularly challenging in subsurface environments, which may be more dangerous for human access and where communication with the surface is limited. Subsurface robotic exploration, which has been to date very limited, is interesting not only for science but also for cost-effective industrial exploitation of resources and safety assessments in mines. Furthermore, it has a direct application to exploration of extra-terrestrial subsurface environments of astrobiological and geological significance such as caves, lava tubes, impact or volcanic craters and subglacial conduits, for deriving in-situ mineralogical resources and establishing preliminary settlements. However, the technological solutions are generally tailor-made and are therefore considered as costly, fragile and environment-specific, further hindering their extensive and effective applications. To demonstrate the advantages of rover exploration for a broad-community, we have developed KORE (KOmpact Rover for Exploration); a low-cost, re-usable, rover multi-purpose platform. The rover platform has been developed as a technological demonstration for extra-terrestrial subsurface exploration and terrestrial mining operations pertaining to geomorphological mapping, environmental monitoring, gas leak detections and search and rescue operations in case of an accident. The present paper, the first part of a series of two, focuses on describing the development of a robust rover platform to perform dedicated geomorphological, astrobiological and mining tasks. KORE was further tested in the Mine Analogue Research 6 (MINAR6) campaign during September 2018 in the Boulby mine (UK), the second deepest potash mine in Europe at a subsurface depth of 1.1 km, the results of which will be presented in the second paper of this series. KORE is a large, semi-autonomous rover weighing 160 kg with L × W × H dimensions 1.2 m × 0.8 m × 1 m and a payload carrying capacity of 100 kg using 800 W traction power that can power to a maximum speed of 8.4 km h⁻¹. The rover can be easily dismantled in three parts facilitating its transportation to any chosen site of exploration. Presently, the main scientific payloads on KORE are: (1) a three-dimensional mapping camera, (2) a methane detection system, (3) an environmental station capable of monitoring temperature, relative humidity, pressure and gases such as NO₂, SO₂, H₂S, formaldehyde, CO, CO₂, O₃, O_2, volatile organic compounds and particulates and (4) a robotic arm. Moreover, the design of the rover allows for integration of more sensors as per the scientific requirements in future expeditions. At the MINAR6 campaign, the technical readiness of KORE was demonstrated during 6 days of scientific research in the mine, with a total of 22 h of operation.