Abstract The plumes discovered by the Cassini mission emanating from the south pole of Saturn׳s moon Enceladus and the unique chemistry found in them have fueled speculations that Enceladus may harbor life. The presumed aquiferous fractures from which the plumes emanate would make a prime target in the search for extraterrestrial life and would be more easily accessible than the moon׳s subglacial ocean. A lander mission that is equipped with a subsurface maneuverable ice melting probe will be most suitable to assess the existence of life on Enceladus. A lander would have to land at a safe distance away from a plume source and melt its way to the inner wall of the fracture to analyze the plume subsurface liquids before potential biosignatures are degraded or destroyed by exposure to the vacuum of space. A possible approach for the in situ detection of biosignatures in such samples can be based on the hypothesis of universal evolutionary convergence, meaning that the independent and repeated emergence of life and certain adaptive traits is wide-spread throughout the cosmos. We thus present a hypothetical evolutionary trajectory leading towards the emergence of methanogenic chemoautotrophic microorganisms as the baseline for putative biological complexity on Enceladus. To detect their presence, several instruments are proposed that may be taken aboard a future subglacial melting probe. The “Enceladus Explorer” (EnEx) project funded by the German Space Administration (DLR), aims to develop a terrestrial navigation system for a subglacial research probe and eventually test it under realistic conditions in Antarctica using the EnEx-IceMole, a novel maneuverable subsurface ice melting probe for clean sampling and in situ analysis of ice and subglacial liquids. As part of the EnEx project, an initial concept study is foreseen for a lander mission to Enceladus to deploy the IceMole near one of the active water plumes on the moon׳s South-Polar Terrain, where it will search for signatures of life. The general mission concept is to place the Lander at a safe distance from an active plume. The IceMole would then be deployed to melt its way through the ice crust to an aquiferous fracture at a depth of 100m or more for an in situ examination for the presence of microorganisms. The driving requirement for the mission is the high energy demand by the IceMole to melt through the cold Enceladan ices. This requirement is met by a nuclear reactor providing 5kW of electrical power. The nuclear reactor and the IceMole are placed on a pallet lander platform. An Orbiter element is also foreseen, with the main function of acting as a communications relay between Lander and Earth. After launch, the Lander and Orbiter will perform the interplanetary transfer to Saturn together, using the on-board nuclear reactor to power electric thrusters. After Saturn orbit insertion, the Combined Spacecraft will continue using Nuclear Electric Propulsion to reach the orbit of Enceladus. After orbit insertion at Enceladus, the Orbiter will perform a detailed reconnaissance of the South-Polar Terrain. At the end of the reconnaissance phase, the Lander will separate from the Orbiter and an autonomously guided landing sequence will place it near one of the active vapor plumes. Once landed, the IceMole will be deployed and start melting through the ice, while navigating around hazards and towards a target subglacial aquiferous fracture. An initial estimation of the mission׳s cost is given, as well as recommendations on the further development of enabling technologies. The planetary protection challenges posed by such a mission are also addressed.
Highlights We present a lander mission to deploy the IceMole melting probe on Enceladus. We introduce the EnEx Project and describe the current IceMole design. A nuclear reactor will be used to power electric thrusters and then the IceMole. A lander will deploy the IceMole and an Orbiter will perform recon and data relay. Autonomous landing and a small nuclear reactor are mission enabling technologies.
A lander mission to probe subglacial water on Saturn׳s moon Enceladus for life
Acta Astronautica ; 106 ; 63-89
2014-09-20
27 pages
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
(N)EP , (Nuclear) Electric Propulsion , ACTC , Attitude Control Thruster Cluster , ASRG , Advanced Stirling Radioisotope Generator , AU , Astronomical Unit , C&DH , Command and Data Handling , EnEx , Enceladus Explorer project , EOI , Enceladus Orbit Insertion , EOM , End of Mission , FY , Fiscal Year , GHe , Helium gas , GN&C , Guidance, Navigation and Control , GPR , Ground Penetrating Radar , HDA , Hazard Detection and Avoidance , HGA , High Gain Antenna , IMU , Inertial Measurement Unit , IPR , Ice Penetrating Radar , <italic>I</italic> <inf>sp</inf> , Specific Impulse , kWe , kilowatt electric , kWt , kilowatt thermal , LGA , Low Gain Antenna , LIDAR , Light Detection and Ranging (“LIght raDAR”) , LV , Launch Vehicle , MAG-L , Magnetometer-Lander , MCT , Minimal Convergent Trait , MEA , Main Engine Assembly , MGA , Medium Gain Antenna , MLI , Multi-layer Insulation , MMRTG , Multi-Mission Radioisotope Thermoelectric Generator , NSF , National Science Foundation , PCA , Pressure Control Assembly , PFCA , Propellant Flow Control Assembly , RC , Reconnaissance Camera , <italic>R</italic> <inf>ENC</inf> , Enceladus Radii , <italic>R</italic>OM , Rough Order of Magnitude , RPS , Radioisotope Power Source , R<inf>S</inf> , Saturn Radii , RTG , Radioisotope Thermoelectric Generator , SEP , Solar Electric Propulsion , SIS , Site Imaging System , SOI , Saturn Orbit Insertion , SPT , South-Polar Terrain , TBR , to be refined , TM , Thermal Mapper , TRL , Technology Readiness Level , Enceladus , Lander , Melting probe , Astrobiology , Icy moons
A lander mission to probe subglacial water on Saturn׳s moon Enceladus for life
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