The presence of oceans on the outer solar system moons Europa and Enceladus poses the question of whether microbial life might be present on those bodies. One approach to answering that question could be a very compact, lightweight and robust microscope that is capable of rapidly imaging the contents of a 3-dimensional sample volume. To this end, we have been developing deployable digital holographic microscopes, which can also be used in the short term for terrestrial field work. A very stable “common-mode” microscope, in which two adjacent beams share several optics, has shown very good imaging performance, and has been deployed successfully to several field sites, including Greenland and Alaska. A more compact approach is our version of the lensless digital holographic microscope, which uses gradient index rod lenses to produce a pair of high numerical-aperture input beams. Sub-micron resolution has been obtained with both systems, and further performance improvements are possible.