Abstract
The evolution of the solar system and the origin of life remain some of the most intriguing questions for humankind. Addressing these questions experimentally is challenging due to the difficulty of mimicking environmental conditions representative for Early Earth and/or space conditions in general in ground-based laboratories. Performing experiments directly in space offers the great chance to overcome some of these obstacles and to possibly find answers to these questions. Exposure platforms in Low Earth Orbit (LEO) with the possibility for long-duration solar exposure are ideal for investigating the effects of solar and cosmic radiation on various biological and non-biological samples. Up to now, the Exobiology and space science research community has successfully made use of the International Space Station (ISS) via the EXPOSE facility to expose samples to the space environment with subsequent analyses after return to Earth. The emerging small and nanosatellite market represents another opportunity for astrobiology research as proven by the robotic O/OREOS mission, where samples were monitored in-situ, i.e. in Earth orbit. In this framework, the European Space Agency is developing a novel Exobiology facility outside the ISS. The new platform, which can host up to four different experiments, will combine the advantages of the ISS (long-term exposure, sample return capability) with near-real-time in-situ monitoring of the chemical/biological evolution in space. In particular, ultraviolet–visible (UV–Vis) and infrared (IR) spectroscopy were considered as key non-invasive methods to analyse the samples in situ. Changes in the absorption spectra of the samples developing over time will reveal the chemical consequences of exposure to solar radiation. Simultaneously, spectroscopy provides information on the growth rate or metabolic activities of biological cultures. The first quartet of experiments to be performed on-board consists of IceCold, OREOcube and Exocube (dual payload consisting of ExocubeChem and ExocubeBio). To prepare for the development of the Exobiology facility, ground units of the UV–Vis and IR spectrometers were studied, manufactured and tested as precursors of the flight units. The activity led to a modular in-situ spectroscopy platform able to perform different measurements (e.g. absorbance, optical density, fluorescence measurements) at the same time on different samples. We describe here the main features of the ground model platform, the verification steps, results and approach followed in the customization of commercial–off-the-shelf (COTS) modules to make them suitable for the space environment. The environmental tests included random and shock vibration, thermal vacuum cycles in the range −20 °C to +40 °C and irradiation of the components with a total dose of 1800 rad (18 Gy). The results of the test campaign consolidated the selection of the optical devices for the Exobiology Facility. The spectroscopic performance of the optical layout was tested and benchmarked in comparison with state-of-the-art laboratory equipment and calibration standards showing good correlation. This includes spectra of samples sets relevant for the flight experiments and a performance comparison between the SPECTROModule ground model and state-of-the-art laboratory spectrometers. Considering the large number of samples and different types of optical measurements planned on-board the ISS, the main outcome was the implementation of an LED-photodiode layout for the optical density and fluorescence measurements of IceCold (42 samples) and ExocubeBio (111 samples); while the UV–Vis spectrometer will be mainly focused on the change of the absorption spectra of the 48 samples of OREOcube.The ExocubeChem samples (in total 48) will be analysed by infrared spectroscopy. The ground platform supports the establishment of analogue research capabilities able to address the long-term objectives beyond the current application.
Highlights
Since the early 1990’s there is a long heritage of European Space Agency (ESA) astrobiology experiments in Low Earth Orbit (LEO), initially using the freeflying EURECA facility, deployed and retrieved by the Space Shuttle, followed by six short-duration BIOPAN missions on unmanned Foton capsules and three longduration EXPOSE missions on the International Space Station (ISS) [1], Figure 1.The earlier BIOPAN and EXPOSE facilities exposed a variety of microorganisms to investigate the effect of LEO environmental parameters, namely short wavelength solar UV, ionizing radiation and temperature oscillation in addition to the desiccating effect of space vacuum or a simulated Mars atmosphere consisting of a Mars gas at 600-1000 Pa pressure
We describe here the main features of the ground model platform, the verification steps, results and approach followed in the customization of commercial–off-the-shelf (COTS) modules to make them suitable for the space environment
Considering the large number of samples and different types of optical measurements planned on-board the ISS, the main outcome was the implementation of an Light-Emitting Diode (LED)-photodiode layout for the optical density and fluorescence measurements of IceCold (42 samples) and ExocubeBio (111 samples); while the UV-Vis spectrometer will be mainly focused on the change of the absorption spectra of the 48 samples of OREOcube .The ExocubeChem samples will be analysed by infrared spectroscopy
Summary
Since the early 1990’s there is a long heritage of ESA astrobiology experiments in LEO, initially using the freeflying EURECA facility, deployed and retrieved by the Space Shuttle, followed by six short-duration BIOPAN missions on unmanned Foton capsules and three longduration EXPOSE missions on the ISS [1], Figure 1.The earlier BIOPAN and EXPOSE facilities exposed a variety of microorganisms (amongst other samples) to investigate the effect of LEO environmental parameters, namely short wavelength solar UV, ionizing radiation and temperature oscillation in addition to the desiccating effect of space vacuum or a simulated Mars atmosphere consisting of a Mars gas at 600-1000 Pa pressure. The facilities were designed to support the investigation of the survival of microorganisms of harsh space and Mars conditions, and of the possibility of viable organisms to travel in space or to Mars, accidentally as blind passengers on a spaceship (planetary protection relevance) or naturally ((litho)panspermia) These missions have provided a unique set of data to understand the influence of UV, cosmic radiation, vacuum, microgravity and thermal excursions on a wide variety of organic compounds and life forms. A new generation of space experiments intends to investigate the response of metabolically active organisms capable of repairing damage induced by space conditions, like short wavelength UV and radiation Since these active cultures may develop and grow during the mission, in contrast to the passively exposed organisms, the investigation after the mission on the ground is no longer sufficient to understand the effects of these extreme environments.
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