OrganiCam: A lightweight time-resolved panoramic fluorescence imager and Raman spectrometer for icy world organic detection and characterization

Ocean worlds including Europa, Enceladus, and to a lesser extent Ceres are targets in the search for biomaterials outside of Earth because the existence of stable, long-lived oceans and sources of energy imply a habitable environment. Characterization of the icy surfaces is a first step in exploration of the contents of the oceans contained below. Fortunately, there is strong evidence of transport of material from the oceans to the surfaces in the form of geysers (plumes) and resurfacing along fractures. Biomaterials, if they exist in the oceans, should be evident from exploring young icy surfaces. Organic molecules and especially biosignatures tend to exhibit prompt fluorescence that can be distinguished from mineral luminescence by its rapid quenching on the order of a few ns. Thus, time-resolved fluorescence spectroscopy can uniquely identify organics on icy surfaces. A pulsed laser provides the best time-resolved stimulation, and synchronization and nanosecond time gating of the detector provides the discrimination needed to distinguish organics from fluorescing minerals. This technique is being used in the Mars 2020 / SuperCam flight instrument in point mode. For the ocean worlds, operations are more difficult and so we propose time-resolved fluorescence panoramic imaging, which can immediately identify organic concentrations in the vicinity of a lander such as that being considered for Europa. For imaging mode, the laser is diffused over the imaged region as demonstrated by the U. Hawaii Biofinder instrument. Detection of organics will be in the part per million range due to the strong fluorescence response, and spatial resolution will be in the submillimeter range. OrganiCam also contains a spectrometer for passive visible-range, and active fluorescence, and Raman spectra. For the latter, the laser diffuser is removed, providing sufficient stimulation for detection of the weaker Raman organic signatures. To initiate OrganiCam spectrometer calibration data sets, we have exposed bacteria, deinococcus radiodurans (radio-resistant) and E. coli to radiation. These damaged procaryotes were sequenced and will be scanned by spectroscopy to calibrate radiation-exposed biosignatures.