Implementing bioburden reduction and control on the deliquescent hydrogel of the HABIT/ExoMars 2020 instrument

Thasshwin Mathanlal*, Miracle Israel Nazarious, Abhilash Vakkada Ramachandran, Maria-Paz Zorzano, Javier Martin-Torres, Petra Rettberg

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)
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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.
Original languageEnglish
Pages (from-to)232-239
Number of pages8
JournalActa Astronautica
Early online date21 Apr 2020
Publication statusPublished - Aug 2020

Bibliographical note

The authors of the paper would like to thank the Institute of Aerospace Medicine, DLR, Germany for their support to analyse the bioburden assay of the HABIT BOTTLE salt mixtures. The authors would also like to acknowledge Roberto Mantas-Nakhai for his contribution during the bioburden assay validation. HABIT is an instrument of the Luleå University of Technology (LTU), led by J. MartínTorres (PI) and M-P. Zorzano (co-PI). The HABIT FM and EQM were fabricated by Omnisys, Sweden, under advice of LTU as part of the HABIT project development and funded by the Swedish National Space Agency (SNSA). M-P. Z's contribution has been partially supported by the Spanish State Research Agency (AEI) Project No. MDM-2017-0737 Unidad de Excelencia “María de Maeztu” - Centro de Astrobiología (INTA-CSIC). We acknowledge the Luleå University of Technology, the Wallenberg Foundation and the Kempe Foundation for support of the Mars research activities. We thank the ExoMars project team, European Space Agency (ESA), Roscosmos, Space Research Institute (IKI) and Omnisys Instruments AB for their hard work on the ExoMars 2022 mission. We acknowledge the Luleå University of Technology, the Wallenberg Foundation and the Kempe Foundation for support of the Mars research activities. The SpaceQ chamber has been developed together with Kurt J. Lesker Company and was funded by the Kempe Foundation.


  • Planetary protection
  • Bioburden control
  • Bioburden assay
  • Dry heat microbial reduction


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