A wideband microscope for detecting and analyzing extraterrestrial life in the solar system

This paper presents a wideband microscope designed for the detection and analysis of extraterrestrial microorganisms within the solar system. An example of a conceptual design for a wideband microscope capable of observing the same field of view in the UV, VIS, and IR is shown; subsequently, the breadboard model (BBM) of the developed UV-VIS-IR microscope (UMI) is presented. To demonstrate deep UV microscopy (275 nm excitation) using the UMI-BBM, we observed a biological sample of sliced squid alongside four types of fluorescent mineral samples and compared the time-dependent changes in the images. As a result, the images of the sliced squid changed color over time, whereas those of all the mineral samples remained stable. We also presented the development of near-infrared (NIR) microscopic imaging spectroscopy and its required hardware for distinguishing organic matter from minerals. In the discussion, we first focused on the combination of microscopy with other methods: its combination with a mass spectrometer is complementary and highly effective. When designing life-detection missions for solar system exploration, ensuring scientific value—even in the event of a null result in the search for life—is crucial for the realization of the project. In life-exploration missions, it is meaningful to distinguish between 'Earth-kin life' (extraterrestrial life sharing a common ancestry with Earth life) and 'Earth-independent life' (extraterrestrial life that emerged independently of Earth life). We considered that if proliferation or autonomous movement is observed in the search for extraterrestrial life, it would serve as compelling evidence of life, depending on its appearance. Subsequently, we described that the use of fluorescent dyes in microscopy for extraterrestrial exploration of microorganisms offers advantages but also poses multiple concerns. The dye-free method presented in this study for identifying biological and mineral samples has the potential to serve as a solution to these concerns.