ROV grade in situ mass spectrometer (ISMS)

The development of the new in-situ mass spec (ISMS) is a cooperation between MARUM and MPI-MM Bremen (Department of Symbiosis - Prof. N. Dubilier). The system is based on one designed to operate at hydrothermal vents (GirguisLab, Harvard University, US) and is suitable for deep-sea ROV deployments (up to 4000m), mainly from both MARUM ROVs QUEST & SQUID. Future deployments might also include CTD casts and/or an integration into mid- to long-term observatories.

Within this project, the initial setup (hardware components and software architecture) was considerably modified and by this, turning the instrument into a new prototype. The upgrades to the ISMS significantly expand its analytical capabilities, reliability, and usability in deep-sea environments. A major innovation is the integration of a cryo-trap for water vapor, which improves the system’s vacuum and thereby significantly lowers detection limits for trace gases such as methane (CH₄). In addition to enhancing performance, the cryo-trap also acts as an emergency safeguard, protecting the ISMS from water intrusion by freezing out water in the event of membrane failure.

To complement this, a new membrane inlet system has been developed using optimized membrane materials that greatly reduce the detection limits. The system supports two membrane types tailored to deployment depth: a thin membrane for fast response in water depths of up to 1000m, and a thicker membrane suitable for extreme depths of up to 4000m.

These upgrades enable both quantitative and qualitative analyses under in situ conditions. A new automated lab calibration unit allows precise adjustment across a wide range of gas types, pressures (up to 400 bar), temperatures, and sample water flow rates. For field operations, an in situ calibration system has been developed, using a in-house developed valve box and gas-tight calibration bags and by this allows real-time calibration with known gas mixtures under actual temperature and pressure conditions at depth.

Control and data management have also been substantially improved through the development of new software tools tailored to expedition workflows. The ISMS Controller enables full operation of the system via ship-wide LAN, allowing scientists to control the ISMS via telepresence in future. The ISMS dashboard provides real-time data visualization and ship-wide access.

The ISMS provides real-time information and guidance for water and sediment sampling during ROV dives. The in-situ MS quantifies dissolved volatiles of masses up to 100. It is suitable for water depths of up to 4000 m and for the analysis of fluids with temperatures up to 400°C. The system was initially tested and deployed with MARUM ROV QUEST 4000 during cruises MSM109, M190, MSM125 and M210 on deep-sea hydrothermal vents. The ISMS is now a standard tool for the MARUM ROVs SQUID and the new QUEST 5000.