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Thera Macula may be a region of active chaos formation above a large liquid water lens. Topographic data indicates that Thera is low-lying, suggesting subsurface water today. Galileo image at 220 m/pixel resolution.
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Abstract The prospect of a future soft landing on the surface of Europa is enticing, as it would create science opportunities that could not be achieved through flyby or orbital remote sensing, with direct relevance to Europa's potential habitability. Here, we summarize the science of a Europa lander concept, as developed by our NASA-commissioned S...
Citations
... Planned missions for the near-future that include mass spectrometers for atmospheric investigation are, amongst others, JUICE, the JUpiter ICy moons Explorer [29], Europa Clipper [77], Comet Interceptor [95], and Dragonfly. The Neutral Ion Mass spectrometer (NIM), part of the Particle Environment Package (PEP) onboard JUICE set for launch in 2022, will conduct the first-ever direct sampling of the exospheres of Europa, Ganymede, and Callisto [8]. ...
So far no designated mission to either of the two ice giants, Uranus and Neptune, exists. Almost all of our gathered information on these planets comes from remote sensing. In recent years, NASA and ESA have started planning for future mission to Uranus and Neptune, with both agencies focusing their attention on orbiters and atmospheric probes. Whereas information provided by remote sensing is undoubtedly highly valuable, remote sensing of planetary atmospheres also presents some shortcomings, most of which can be overcome by mass spectrometers. In most studies presented to date a mass spectrometer experiment is thus a favored science instrument for in situ composition measurements on an atmospheric probe. Mass spectrometric measurements can provide unique scientific data, i.e., sensitive and quantitative measurements of the chemical composition of the atmosphere, including isotopic, elemental, and molecular abundances. In this review paper we present the technical aspects of mass spectrometry relevant to atmospheric probes. This includes the individual components that make up mass spectrometers and possible implementation choices for each of these components. We then give an overview of mass spectrometers that were sent to space with the intent of probing planetary atmospheres, and discuss three instruments, the heritage of which is especially relevant to Uranus and Neptune probes, in detail. The main part of this paper presents the current state-of-art in mass spectrometry intended for atmospheric probe. Finally, we present a possible descent probe implementation in detail, including measurement phases and associated expected accuracies for selected species.
... The spatial resolution of available images suggests the existence of a complex environment at the outcrop-scale on these icy satellites. Therefore, the scientific and logistic preparation of such missions, requires to achieve insights on local-scale settings for the future camera observation at high-resolution (e.g., JUICE/JANUS camera spatial resolution ranges from 400 m/pixel down to <10 m/pixel; Palumbo et al., 2014), and for future lander or even rover that will explore such disrupted surfaces (e.g., Pappalardo et al., 2013). ...
... Raman spectroscopy is an efficient tool that enables nondestructive, fast in situ analysis of molecular vibrational information from gaseous, liquid, and solid materials. Therefore, it is commonly used for investigation of biosignatures from early Earth and has been suggested to be applied in the search for potential extraterrestrial life (Wang et al., 2003;Jorge Villar and Edwards, 2006;Marshall et al., 2010;Pappalardo et al., 2013;Marshall and Marshall, 2014;Qu et al., 2015). Besides deep-space explorations, remotely operated vehicles equipped with Raman spectrometers have already been employed in deep-sea investigations and have helped to detect natural supercritical carbon dioxide from the subsea Yonaguni Knoll IV hydrothermal field in the western Pacific, for example, Brewer et al. (2004) and Zhang et al. (2020). ...
Benefiting from their adaptability to extreme environments, subsurface microorganisms have been discovered in sedimentary and igneous rock environments on Earth and have been advocated as candidates in the search for extraterrestrial life. In this article, we study iron-mineralized microstructures in calcite-filled veins within basaltic pillows of the late Ladinian Fernazza group (Middle Triassic, 239 Ma) in Italy. These microstructures represent diverse morphologies, including filaments, globules, nodules, and micro-digitate stromatolites, which are similar to extant iron-oxidizing bacterial communities. In situ analyses including Raman spectroscopy have been used to investigate the morphological, elemental, mineralogical, and bond-vibrational modes of the microstructures. According to the Raman spectral parameters, iron minerals preserve heterogeneous ultrastructures and crystallinities, coinciding with the morphologies and precursor microbial activities. The degree of crystallinity usually represents a microscale gradient decreasing toward previously existing microbial cells, revealing a decline of mineralization due to microbial activities. This study provides an analog of possible rock-dwelling subsurface life on Mars or icy moons and advocates Raman spectroscopy as an efficient tool for in situ analyses. We put forward the concept that ultrastructural characteristics of minerals described by Raman spectral parameters corresponding to microscale morphologies could be employed as carbon-lean biosignatures in future space missions.
... The presence of SC8.5 in surface materials could be used to identify and characterize regions of extrusion of oceanic material frozen at depth. Such an indicator of vertical exchange would aid in the search for biosignatures by upcoming missions such as ESA's JUICE, NASA's Europa Clipper and DragonFly (7)(8)(9), and future landers (48,49). ...
Sodium chloride is expected to be found on many of the surfaces of icy moons like Europa and Ganymede. However, spectral identification remains elusive as the known NaCl-bearing phases cannot match current observations, which require higher number of water of hydration. Working at relevant conditions for icy worlds, we report the characterization of three "hyperhydrated" sodium chloride (SC) hydrates, and refined two crystal structures [2NaCl·17H2O (SC8.5); NaCl·13H2O (SC13)]. We found that the dissociation of Na+ and Cl- ions within these crystal lattices allows for the high incorporation of water molecules and thus explain their hyperhydration. This finding suggests that a great diversity of hyperhydrated crystalline phases of common salts might be found at similar conditions. Thermodynamic constraints indicate that SC8.5 is stable at room pressure below 235 K, and it could be the most abundant NaCl hydrate on icy moon surfaces like Europa, Titan, Ganymede, Callisto, Enceladus, or Ceres. The finding of these hyperhydrated structures represents a major update to the H2O-NaCl phase diagram. These hyperhydrated structures provide an explanation for the mismatch between the remote observations of the surface of Europa and Ganymede and previously available data on NaCl solids. It also underlines the urgent need for mineralogical exploration and spectral data on hyperhydrates at relevant conditions to help future icy world exploration by space missions.
... A landed mission is a likely next step, and detailed concept studies have already investigated how to directly search for evidence of life in the upper tens of centimeters of Europa's icy regolith (Korablev et al. 2011;Pappalardo et al. 2013;Hand et al. 2017;Blanc et al. 2020). However, it is the subsurface reservoirs of liquid water within the ice shell and the ocean below that are the most likely regions to maintain presently habitable conditions for extant life (e.g., Schmidt et al. 2011;Michaut & Manga 2014). ...
... Europa Clipper and JUICE will provide subsurface reconnaissance of Europa through surface imaging and radar-based structural mapping in the ice shell. Subsequent landed missions would further bound Europa's interior with seismic sounding (Pappalardo et al. 2013;Hand et al. 2017) or electromagnetic (EM) methods (Pappalardo et al. 2013;Grimm et al. 2021). A lander may additionally be augmented with a small-scale (class 1; <10 m) penetrator (e.g., Biele et al. 2011) to sample the upper meters of the ice shell or demonstrate preliminary subsurface access technology, as advocated for in Schmidt et al. (2021a). ...
... Europa Clipper and JUICE will provide subsurface reconnaissance of Europa through surface imaging and radar-based structural mapping in the ice shell. Subsequent landed missions would further bound Europa's interior with seismic sounding (Pappalardo et al. 2013;Hand et al. 2017) or electromagnetic (EM) methods (Pappalardo et al. 2013;Grimm et al. 2021). A lander may additionally be augmented with a small-scale (class 1; <10 m) penetrator (e.g., Biele et al. 2011) to sample the upper meters of the ice shell or demonstrate preliminary subsurface access technology, as advocated for in Schmidt et al. (2021a). ...
Several worlds in our solar system are thought to hold oceans of liquid water beneath their frozen surfaces. These subsurface ice and ocean environments are promising targets in the search for life beyond Earth, but they also present significant new technical challenges to planetary exploration. With a focus on Jupiter’s moon Europa, here we (1) identify major benefits and challenges to subsurface ocean world science, (2) provide a multidisciplinary survey of relevant sample handling and life detection technologies, and (3) integrate those perspectives into the Subsurface Science and Search for Life in Ocean Worlds (SSSLOW) concept payload. We discuss scientific goals across three complementary categories: (1) search for life, (2) assess habitability, and (3) investigate geological processes. Major mission challenges considered include submerged operation in high-pressure environments, the need to sample fluids with a range of possible chemical conditions, and detection of biosignatures at low concentrations. The SSSLOW addresses these issues by tightly integrated instrumentation and sample handling systems to enable sequential, complementary measurements while prioritizing preservation of sample context. In this work, we leverage techniques and technologies across several fields to demonstrate a path toward future subsurface exploration and life detection in ice and ocean worlds.
... However, the two space agencies separated, leading to two non-harmonized missions, NASA's Europa Clipper [8], slated for launch in 2024, and ESA's JUpiter ICy moons Explorer (JUICE) [9], to lift off in 2023. Eventually, a second mission to Europa, Europa Lander, is being studied by NASA: it aims at analyzing soil composition [10] via in-situ techniques. While JUICE and Europa Clipper are slated for launch respectively in 2023 and 2024, discussion about Europa Lander feasibility has been recently postponed to 2032 [11]. ...
A transfer solution targeting Callisto is presented and analyzed in this paper. Both the interplanetary and the jovocentric transfers are optimized with simplified two body models, accounting for complex transfer strategies. The former combines swing-bys and impulsive Deep Space Maneuvers to reach Jupiter sphere of influence with restrained costs; the chosen planet sequence exploits Earth flybys only, maintaining distance from Sun and requiring planetary phasing of Earth only with the target planet. Transfer within Jupiter sphere of influence builds on alternating flybys about Callisto with apojove kick maneuvers, leveraging v∞ at every moon encounter. Insertion costs about Jupiter are further lowered employing a flyby about Ganymede. Interplanetary travel is optimized with state-of-the-art Particle Swarm Optimization, whereas the v∞ leveraging sequence limits the apojove kick maneuvers authority to a fixed threshold.
... Specifications are mission-dependent. However, lower limits of detection (LOD) of 1 ppb (Mahaffy et al., 2012;Pappalardo et al., 2013) or even lower (Hand et al., 2017;MacKenzie et al., 2022b) are often required. ...
... This is demonstrated by the chemical degradation of organics at elevated temperatures in the presence of perchlorates and the inhibitory matrix effects of minerals during derivatization (Navarro-González et al., 2006;Stalport et al., 2012). Furthermore, current instrumentation is not fit for the purpose in regards to targeted LODs (ca. 1 ppb) of key organic biosignatures such as fatty acids, amino acids, and informational polymers (i.e., DNA and RNA; Mahaffy et al., 2012;Pappalardo et al., 2013;Hand et al., 2017;Neveu et al., 2018). On the basis of the summary of previously used in situ organic detection techniques, further development is needed in order to detect a greater span of organic biosignatures at lower concentrations than what is currently possible. ...
... However, their simplicity and ability to interrogate Frontiers in Astronomy and Space Sciences frontiersin.org a vast number of samples will render them invaluable for sample selection for further analysis by instruments that are limited by the number of samples that can be analyzed. On the basis of the reviewed literature, the next-generation biosignature detection techniques for planetary applications (CE, LC, biosensors, and nanopore sensing) are mostly fit for science requirements in mission concepts that include life detection (Pappalardo et al., 2013;Hand et al., 2017;MacKenzie et al., 2022a;MacKenzie et al., 2022b;Williams and Muirhead, 2022). Current GC-MS, fluorescence, and Raman spectroscopy instruments cannot achieve the required LODs. ...
The search for life in Solar System bodies such as Mars and Ocean Worlds (e.g., Europa and Enceladus) is an ongoing and high-priority endeavor in space science, even ∼ five decades after the first life detection mission at Mars performed by the twin Viking landers. However, the in situ detection of biosignatures remains highly challenging, both scientifically and technically. New instruments are being developed for detecting extinct or extant life on Mars and Ocean Worlds due to new technology and fabrication techniques. These instruments are becoming increasingly capable of both detecting and identifying in situ organic biosignatures that are indicative of life and will play a pivotal role in the search for evidence of life through robotic lander missions. This review article gives an overview of techniques used for space missions (gas chromatography, mass spectrometry, and spectroscopy), the further ongoing developments of these techniques, and ion mobility spectrometry. In addition, current developments of techniques used in the next-generation instruments for organic biosignature detection are reviewed; these include capillary electrophoresis, liquid chromatography, biosensors (primarily immunoassays), and nanopore sensing; whereas microscopy, biological assays, and isotope analysis are beyond the scope of this paper and are not covered.
... Identifying where nutrient-open, nutrient-closed, and relict potential habitats could exist in Europa's ice shell can guide future life-detection missions, such as a Europa lander (R. Pappalardo et al., 2013). Our study demonstrates that relict potential habitats represent the most accessible targets for future missions to sample biosignatures at Europa. ...
Brine systems in Europa's ice shell have been hypothesized as potential habitats that could be more accessible than the sub‐ice ocean. We model the distribution of sub‐millimeter‐scale brine pockets in Europa's ice shell. Through examination of three habitability metrics (water activity, ionic strength, and salinity), we determine that brine pockets are likely not geochemically prohibitive to life as we know it for the chloride and sulfate‐dominated ocean compositions considered here. Brine volume fraction is introduced as a novel habitability metric to serve as a proxy for nutrient transport and recycling—because of its role in governing permeability—and used to define regions where nutrient‐open, nutrient‐closed, and relict habitats are stable. Whereas nutrient‐closed habitats could exist wherever brine is stable, nutrient‐open habitats are confined to meter‐scale regions near the ice‐ocean interface where freezing is occurring. This classification scheme can help guide future life‐detection missions to ocean worlds.
... One such application currently under consideration is a power source for a lander to the surface of Europa, a moon of Jupiter, where a significant amount of liquid water is believed to be located under an icy shell. 3 Exploration of this moon is a high priority for the space science community; however, powering such a mission remains a challenge. The distance is too great to utilize current solar arrays of sufficient size in a highly mass-constrained lander. ...
Lithium-carbon monofluoride (Li/CFx) D-sized battery cells discharged at very low rates (C/1800) were found to deliver inconsistent capacities. These effects were found to be absent as the discharge rate was increased to C/600. Destructive physical analysis of the cells discharged at C/1800 confirmed the effects of corrosion, manifesting as preferential utilization of the Li anode around the copper current collector, discoloration of the remaining excess Li, and more crucially loss of adhesion to the copper current collector, resulting in a premature completion of discharge. This anomalous behavior may be attributed to the competing corrosion reaction at the Li anode during discharge, whereby Li+ is lost to the electrolyte at a rate that is similar to the competing current-producing charge transfer process. At higher rates, this corrosion process is masked by the more significant discharge current generated by the full cell, which occurs at a much higher rate. The inconsistent capacity delivery may relate to the uneven breakdown of the surface film at these very low rates, where the current density is very low. Experimental data from both D-sized and three-electrode cells describing this effect are presented, as well as possible remedies for cells where very low discharge rates are desired.
... Missions to ocean worlds in particular are confronted with long communication delays (e.g., 70-90 min between Earth and Titan), low bandwidth for data transmission, and potentially low power or energy supply, all of which decrease data transfer rates and volumes. In addition, missions to these targets will have protracted time intervals for data analysis and ground-in-the-loop, day-to-day decision-making (e.g., *6 h between operational decisions, Europa lander: Pappalardo et al., 2013;Hand et al., 2017). Targets such as Europa have the additional challenge of an extreme radiation environment (Marion et al., 2003), which will limit mission lifetimes and therefore the time to implement science-driven data collection strategies. ...
... Continued radiation exposure results in lighter coloration (Hand and Carlson, 2015;Schmidt, 2020). Either region's young surface could express material from the sub-ice ocean or intra-ice liquid pockets and therefore is considered an ideal surface target for astrobiology exploration (Kereszturi and Keszthelyi, 2013;Pappalardo et al., 2013;Hand et al., 2017). The proposed Europa lander intends to employ autonomous software similar to the EDL system used on MSL and Mars 2020 to identify surface characteristics (engineering constraints: e.g., large blocks of ice, steep inclines) and autonomously choose a favorable site for landing. ...
Astrobiology missions to ocean worlds in our solar system must overcome both scientific and technological challenges due to extreme temperature and radiation conditions, long communication times, and limited bandwidth. While such tools could not replace ground-based analysis by science and engineering teams, machine learning algorithms could enhance the science return of these missions through development of autonomous science capabilities. Examples of science autonomy include onboard data analysis and subsequent instrument optimization, data prioritization (for transmission), and real-time decision-making based on data analysis. Similar advances could be made to develop streamlined data processing software for rapid ground-based analyses. Here we discuss several ways machine learning and autonomy could be used for astrobiology missions, including landing site selection, prioritization and targeting of samples, classification of "features" (e.g., proposed biosignatures) and novelties (uncharacterized, "new" features, which may be of most interest to agnostic astrobiological investigations), and data transmission.
