Jonas Kuhn (JPL) - Enabling the Search for Microbial Life in Other Worlds' Oceans with Digital Holographic Microscopy

Extraterrestrial life in our Solar System, if present, is almost certain to be microbial. Methods and technologies for unambiguous detection of living or extinct microorganisms are needed for life-detection missions to the Jovian and Saturnian moons, where liquid water is known to exist. Our research focuses specifically on microbial meaningful motion as a biosignature-"waving crowds" at the micron scale. Digital Holographic Microscopy (DHM) is an excellent tool for unambiguous identification of bacterial and protozoal swimming, even in the presence of turbidity, drift, and currents. DHM uses the interference of light to record and reproduce three-dimensional magnified images of object. This approach has several advantages over ordinary brightfield microscopy that make it ideal for field microbiology, in particular a larger depth of field, hands-off operation, robustness regarding environmental conditions, and large sampling volumes with quantitative 3D records of motility behavior. The challenges of optimizing resolution vs. field of view, and of handling the large volumes of data generated during holographic imaging, are discussed briefly. Tests in Earth analogue environments will establish performance parameters as well as answer scientific questions that traditional microscopic techniques cannot. In addition, this will simultaneously qualify the technology for NASA TRL-5 (test in relevant environment), in preparation for missions instrument proposals.