Data returned from robotic spacecraft on - and around - Mars suggest the existence of abundant sub-surface water-ice deposits at locations and latitudes accessible for future human missions. These findings have significant implications for two of the most compelling reasons for Mars exploration: searching for life elsewhere in the universe, and preparing to send the first humans to another planet.
As opposed to the inhospitable surface, the deep subsurface of Mars is an ionising radiation free environment and provides a pressure and thermal environment that allows water to exist in a stable form, which may in turn provide niche habitable conditions for past (and potentially present day) microorganisms. Subsurface water-ice deposits are also a potentially valuable resource for future human missions if they can be found in accessible locations between the equator and mid-latitudes.
To date subsurface ice deposits on Mars have never been studied in-situ. This environment presents a new frontier for exploration, one with a high potential for breakthrough discoveries. Furthermore, if future human missions are to be able to safely leverage the water-ice deposits on Mars, the presence of water-ice deposits indicated from orbit will need to be confirmed in-situ.
ARMADILLO (Accessing Resources on MArs, Drilling Ice and Looking for Life and Organics) was a pre-phase A study conducted in ESA’s Concurrent Design Facility (CDF) between September - November 2021. The study aimed to assess payload options needed to support a Mars ice-access mission. Assigned to represent Thermal in the study, I was responsible for the full thermal design of the lander and payloads.
The purpose of the proposed mission is to close knowledge gaps for human mission planning related to reconnaissance of Mars resources, to investigate the astrobiological potential of subsurface ice environments, and to develop European in-situ resource utilization (ISRU) capabilities. The mission therefore includes a lander equipped with the DEEPER drilling system science instrumentation, as well as ISRU and fuel-cell demonstration units. The lander is to be capable of operating at latitudes between 0° and 40°N.
Depending on the exact latitude, landing date and mission duration, the thermal environment (ambient temperature, albedo, ground temperature and inertia, etc.) will vary significantly. Therefore the system must be designed to be robust to a wide range of hot and cold cases.
For the hot cases, it is expected that the system will see very high daytime heat loads, driven by the operation of drill, ISRU, fuel cell, and science payloads. To handle these heat loads, the lander includes three independent ExoMars-heritage loop heat pipes to spread heat around the lander. To reach the necessarily high operating temperatures of the fuel cell (800 °C), co-electrolyser (800 °C), and Sabatier reactor (400 °C), a large proportion (322 W) of the power budget is devoted to heater power during their warm-up. To save power for system-critical functions, the mission CONOPS must not include parallel warm-up, drilling and science operations. High-temperature units are insulated from other units with 0.8 kg of high-temperature composite aerogel insulation.
For the cold cases, the system must be capable of surviving Mars nighttime temperatures as low as -130 °C. The main payload ‘warm’ compartment is required to be maintained above -40 °C. Due to the presence of an atmosphere, classical spacecraft multi-layer insulation (MLI) is not suitable for Mars surface missions. For this reason, the entire warm compartment is insulated with 4.5 kg of lightweight hybrid gas-gap insulation. Radioisotope heater units (RHUs) are included to compensate for heat leaks. The drilling mechanism - designed to drill to depths of over 10 meters - must be warmed up with heaters prior to operation. To survive the the night, additional heater power is allocated for freeze-prevention in tanks, piping and pumps.
Landing platform overview in stowed (left) and deployed (right) configurations
Operation steps of the DEEPER drill during one ‘peck’ at the Martian surface
ARMADILLO Thermal Concept Architecture
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I was very lucky to work in the CDF for my first project at ESA. I had the opportunity to learn from - and work with - principal scientists and engineers on flagship ESA Mars missions (past and present). Having full responsibility of the thermal design introduced me to the challenges of surviving the harsh thermal environment on Mars. Overall, an amazing experience!