Periodic Reporting for period 4 - Habitat-OASIS (Habitability of Oceans and Aqueous Systems on Icy Satellites)
Berichtszeitraum: 2021-10-01 bis 2023-04-30
Habitat-OASIS addresses the question of habitability of the outer solar system by looking at space craft data and preparing future space missions using novel approaches. The classical view held that a habitable planet or moon requires liquid water at or near its surface. This view has been challenged by the discovery of numerous subsurface oceans below the icy crusts of ice moons orbiting Jupiter and Saturn in the outer solar system. The amount of water detected there is several times higher than on Earth and is kept liquid not by solar heat but mostly by internal heating. Among them, the cryo-volcanic moons Enceladus at Saturn, and Europa which orbits Jupiter, are considered to have the largest astrobiological potential. On these two moons, the ocean floor is on top of a rocky core and there are indications for hydrothermal activities where hot water flows out from the rocky sea floor into the ocean. On Earth, these kinds of hydrothermal vents are places where life developed independently of sunlight.
It is apparent that the search for habitable places on our doorstep, inside our solar system, is important beyond the space science community and is relevant for the society in a more general sense. By understanding the habitability of icy ocean worlds, the ambitious ERC projects will translate to the habitability of the Universe in general, because icy moons orbiting giant planets should be fairly common in our galaxy. Consequently, this work will open up fundamental perspectives: if habitable conditions can occur at remote places like on ‘tiny’ Enceladus, we may have drastically underestimated the life-friendliness of our universe. Habitat-OASIS aims to explore the habitability of these worlds using in situ compositional data from current and future space missions.
On Enceladus (and probably also on Europa), the ice grains expelled by active plumes carry matter previously dissolved and suspended in the subsurface oceans, allowing constraining their geochemistry. The mass spectrometers aboard the Cassini-Huygens spacecraft orbiting Saturn until fall 2017 analyzed this material and already delivered spectacular science results. Project 1 of this proposal is the refined data analysis of the Enceladus plume material using novel techniques and is the first ever opportunity to explore in detail a potential ocean habitat outside Earth. Newly developed laser-assisted dispersion experiments are used to acquire mass spectra on a wide variety of analogue materials, enabling the identification and quantification of inorganic, organic and possibly biogenic compounds embedded in the ice grains. Geochemical aqueous alteration experiments and numerical modeling help to further constrain the habitability of Enceladus and extrapolate the results to other ocean moons. Project 2 will leverage the laboratory capabilities from Project 1 to create a comprehensive library of mass spectra in preparation of the upcoming missions visiting Jupiter’s icy moons: ESA’s JUICE Mission and NASA’s Europa Clipper Mission. Having analogue measurements available early in the missions will be critical for exploiting their full potential.
It is apparent that the search for habitable places on our doorstep, inside our solar system, is important beyond the space science community and is relevant for the society in a more general sense. By understanding the habitability of icy ocean worlds, the ambitious ERC projects will translate to the habitability of the Universe in general, because icy moons orbiting giant planets should be fairly common in our galaxy. Consequently, this work will open up fundamental perspectives: if habitable conditions can occur at remote places like on ‘tiny’ Enceladus, we may have drastically underestimated the life-friendliness of our universe. Habitat-OASIS aims to explore the habitability of these worlds using in situ compositional data from current and future space missions.
On Enceladus (and probably also on Europa), the ice grains expelled by active plumes carry matter previously dissolved and suspended in the subsurface oceans, allowing constraining their geochemistry. The mass spectrometers aboard the Cassini-Huygens spacecraft orbiting Saturn until fall 2017 analyzed this material and already delivered spectacular science results. Project 1 of this proposal is the refined data analysis of the Enceladus plume material using novel techniques and is the first ever opportunity to explore in detail a potential ocean habitat outside Earth. Newly developed laser-assisted dispersion experiments are used to acquire mass spectra on a wide variety of analogue materials, enabling the identification and quantification of inorganic, organic and possibly biogenic compounds embedded in the ice grains. Geochemical aqueous alteration experiments and numerical modeling help to further constrain the habitability of Enceladus and extrapolate the results to other ocean moons. Project 2 will leverage the laboratory capabilities from Project 1 to create a comprehensive library of mass spectra in preparation of the upcoming missions visiting Jupiter’s icy moons: ESA’s JUICE Mission and NASA’s Europa Clipper Mission. Having analogue measurements available early in the missions will be critical for exploiting their full potential.
In Project 1 we targeted the compositional interpretation of ice grains emerging from the subsurface ocean of Saturn’s small ice moon Enceladus with a number of new experimental and theoretical methods. The data was recorded between 2005 and 2017 by instruments onboard the NASA/ESA Cassini-Huygens space craft. We discovered both organic and inorganic compounds that indicate that Enceladus subsurface ocean is a place with conditions suitable for the emergence of extraterrestrial life. We inferred that the detected complex organics with high probability originate from Enceladus’ hydrothermally active core and can be efficiently transported to the oceanic surface by large-scale convection and bubbles of volatile gases emerging from depth. It is quite likely that the organic material has been processed or produced inside the hydrothermally active core of Enceladus. However, the limited capabilities of the Cassini instruments did not allow a definite conclusion in the question if these organic stem from abiotic or biotic processes. By analyzing salts and minerals in the emitted ice grains we find compound that have been previously dissolved in the ocean. The most remarkable finding here was the discovery of the element phosphorous (P) as a crucial inorganic ingredient for life. We inferred that P is dissolved in Enceladus’ ocean at ≈1000-times higher concentrations than in Earth ocean and with that readily available for development and preservation of potential life forms. Geochemical experiments and modelling carried out with our partners in Japan and the US demonstrated why Enceladus has such a high P-availability in its ocean and therefore by no means is a bottle neck for the potential emergence of life there. These results allowed the prediction of high phosphate availability in other aqueous systems in the outer solar system.
The results of project 1 have often been communicated by media - such as TV, radio, online and printed articles - to a large world-wide audience.
In Project 2 we prepared for the habitability explorations of ocean moons in the Jovian system by future ESA and NASA missions. We investigated how the detection of potential bio signatures with instruments on these space craft would work. We showed that the successor of the Cassini Instrument onboard the Europa Clipper space craft will be capable to detect bio-signatures with high reliability and sensitivity and identified suitable places on the surface or the ocean moon Europa. Within this project we also developed novel and much improved detection methods to distinguish and determine abiotic and biotic organic chemistry by future space missions. Finally, we took part in the development of concepts for new space missions to Enceladus, that look for extraterrestrial life forms on this habitable moon.
The results of project 1 have often been communicated by media - such as TV, radio, online and printed articles - to a large world-wide audience.
In Project 2 we prepared for the habitability explorations of ocean moons in the Jovian system by future ESA and NASA missions. We investigated how the detection of potential bio signatures with instruments on these space craft would work. We showed that the successor of the Cassini Instrument onboard the Europa Clipper space craft will be capable to detect bio-signatures with high reliability and sensitivity and identified suitable places on the surface or the ocean moon Europa. Within this project we also developed novel and much improved detection methods to distinguish and determine abiotic and biotic organic chemistry by future space missions. Finally, we took part in the development of concepts for new space missions to Enceladus, that look for extraterrestrial life forms on this habitable moon.
Our results mark the first ever detection of complex organics from a contemporary, extraterrestrial water-world. We severely constrained the molecular structure and composition of this organic material emerging from depth, and could link these to hydrothermal processes occurring at the interface of the subsurface ocean with the moon’s rocky core. Therefore, in summary, both our findings of complex and simple molecules (Postberg et al., Nature 2018; Khawaja et al., MNRAS 2019) substantially enhance the astrobiological potential of the moon.
We found new constraints on the inorganic compounds dissolved in Enceladus’ ocean, most important the high availability of element phosphorous in the ocean, a critical ingredient for life. Geochemical experiments and modelling carried out with our partners in Japan and the US demonstrated why Enceladus has such a high P-availability in its ocean and therefore by no means is a bottle neck for the potential emergence of life there (Hao et al. 2022; Postberg et al., 2023). These results allowed the prediction of high phosphate availability in other subsurface oceans in the outer solar system.
In the preparation for future missions we provide a unique data base for the identification of inorganic, organic, and biogenic compounds from subsurface oceans. We furthermore develop novel methods for the compositional characterization of these potential habitats and took part in the scientific definition of future space missions looking for life there.
We found new constraints on the inorganic compounds dissolved in Enceladus’ ocean, most important the high availability of element phosphorous in the ocean, a critical ingredient for life. Geochemical experiments and modelling carried out with our partners in Japan and the US demonstrated why Enceladus has such a high P-availability in its ocean and therefore by no means is a bottle neck for the potential emergence of life there (Hao et al. 2022; Postberg et al., 2023). These results allowed the prediction of high phosphate availability in other subsurface oceans in the outer solar system.
In the preparation for future missions we provide a unique data base for the identification of inorganic, organic, and biogenic compounds from subsurface oceans. We furthermore develop novel methods for the compositional characterization of these potential habitats and took part in the scientific definition of future space missions looking for life there.