The instrument HABIT (HabitAbility, Brine Irradiation and Temperature) on the ExoMars platform

HABIT (HabitAbility, Brine Irradiation and Temperature) is an edge- breaking and multipurpose instrument: it is a surface station devoted to evaluating the habitability of Mars, but also an In-situ Resource Utilization instrument for future Mars exploration. The search for present life and habitability on Mars is conditioned by the availability of liquid water. It has recently been shown that liquid water is stable on Mars in the form of brines [Martín-Torres et al., Nature Geoscience 2015]. Two other environmental conditions constrain the habitability of the near surface of Mars, the thermal range and the UV radiation dose [Rummel et al. Astrobiology, 2014]. The HABIT (HAbitability, Brine Irradiation and Temperature) instrument is dedicated to investigating the habitability on present day Mars by quantifying the availability of liquid water, the thermal ranges and UV doses. It includes the BOTTLE (Brine Observation Transition To Liquid Experiment) compartment to capture at night-time atmospheric water by deliquescence of four different types of salts: calcium perchlorate, magnesium perchlorate, sodium perchlorate and calcium chloride, and 3 environmental sensors devoted to monitoring the full diurnal and seasonal variations of the ground and air temperature, and the UV irradiance. These three sensors shall complement the existing environmental package of the spacecraft, which has Pressure and Relative Humidity sensors. HABIT measurements will allow to constrain the habitability at the landing site in terms of metabolic and reproduction temperature, calculating the heat-flux and the UV biological dose, providing the Relative Humidity of the ground and air, to study the atmosphere/surface water interchange, provide information about winds (which shall be useful also for the rover drilling and sampling operations), and about thermal inertia and subsurface thermal profile and hydration level complementing the studies of the other platform and rover instruments. It will also provide the concentration of the atmospheric trace gas ozone (complementing orbiter observations from NOMAD-Trace Gas Orbiter) and atmospheric UV opacity (providing continuous monitoring of the dust cycle). The BOTTLE unit is furthermore designed as an ISRU (In-situ Resource Utilization) demonstrator that shall quantify the amount of water (and derived products such as H _{2 } and O _{2}) available for future landed missions on Mars. HABIT will provide environmental information that will allow for extra-long term climate and atmospheric monitoring and will measure for the first-time liquid water on Mars in a controlled way, while providing ISRU possibilities