Going the Last Kilometer: Overcoming Challenges to Discovering Life-Supporting Gradients on Ocean Worlds

On Earth, submarine volcanism sustains hydrothermal discharge, which in turn creates chemical redox gradients that enable life to thrive in deep-sea oases. Evidence now suggests oceans and volcanism exist on other Ocean Worlds in our Solar System. If similar hydrothermal systems exist on other water worlds, what could it take to locate them? A variety of mission architectures and capabilities will be considered as we move towards robotic exploration of putative Ocean Worlds systems. Our NASA-funded SUBSEA research team examined hydrothermal systems on Earth, specifically at Loihi Seamount and Gorda Ridge, as a means to identify scientific and exploration requirements to support missions to Ocean Worlds such as Enceladus and Europa. This presentation focuses on one aspect of our broader research program, that is the challenge of locating a life-giving deep-sea oasis within the last kilometer of proximity. On Earth, this requires determining thermal and chemical gradients accurately at physical scales on the order of centimeters to meters in water-depths of several kilometers. At present only a few sensing technologies are capable of quantifying hydrothermal anomalies within this proximity zone and not all, at present, would be suitable for exoplanet exploration. We specifically evaluated temperature as a first-order parameter for sensing hydrothermal gradients at Gorda Ridge. In addition, temperature sensing was coupled to an adaptive aqueous sampling routine to retrieve samples for measurements such as redox potential and dissolved oxygen concentrations to characterize the gradients where life can thrive at these deep-sea oases.