Electrochemical Sensors for Understanding Icy Worlds

As NASA explores Ocean Worlds and looks for habitable environments, it will be advantageous to perform liquid analyses of samples because (frozen) aqueous solutions will be the sample’s natural state. As part of these missions, the ability to make bulk and trace soluble inorganic ion measurements will be critical to allow comparative oceanography of different worlds. Ion selective electrodes (ISEs) have demonstrated their value in making soluble ion measurements during the Phoenix lander mission on Mars. This project focuses on incorporating developments in ISE technology in the 10+ years since the Phoenix mission sensors were built in order to allow them to be more effective on upcoming longer duration Ocean Worlds missions.

As the exploration of Ocean Worlds in our Solar System advances a key science requirement will be to understand what observations at the surface tell us about the oceans hidden below. The ability to make bulk and trace soluble inorganic ion measurements will be critical to understand the habitability of these oceans by providing constraints on the redox balance, pH, and chemosynthetic metabolism pathways available in the oceans. Ion selective electrode (ISE) technology is a powerful tool for measuring soluble inorganic ions as demonstrated on the Mars Phoenix lander mission. Sensor technology has been improved in the 10+ years since the development of the Phoenix mission, primarily by the switch to solid contact ISEs (SC-ISEs) using nanostructured carbon materials (e.g., carbon nanotubes, platinum nanoparticles etc.). There are many benefits of SC-ISEs to planetary exploration including improved robustness over the long storage periods needed to travel to the outer solar system, the ability to be reduced in size without compromising sensor lifetime, improved limits-of-detection, and reduction in sensor-to-sensor variability. Our approach will be to incorporate the current state-of-the-art in laboratory SC-ISEs to accrue the benefits listed above, and then perform the necessary testing to bring the sensors to TRL 5.