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Timescales for the accumulation of a significant radiation dose at different depths for several locations on the surface of Europa The energetic electron dose is given in terms of years to reach a significant dose of 100 eV per 16 amu, which is equal to a dose of 603 MGy. The dashed vertical line on the left indicates the maximum penetration depth of cold and suprathermal plasma electrons and ions, which have not been considered in this study. Dose–depth profiles in dosage units are provided in Supplementary Fig. 1.
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Jupiter’s moon Europa, which is thought to possess a large liquid water ocean beneath its icy crust, is one of the most compelling targets in the search for life beyond Earth. Its geologically young surface, along with a number of surface features, indicate that material from Europa’s interior may be emplaced on the surface. However, the surface is...
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The magnetosphere of an exoplanet has yet to be unambiguously detected. Investigations of star–planet interaction and neutral atomic hydrogen absorption during transit to detect magnetic fields in hot Jupiters have been inconclusive, and interpretations of the transit absorption non-unique. In contrast, ionized species escaping a magnetized exoplan...
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... Our group has recently demonstrated that the same irradiation experiment performed at a higher temperature may yield different results (Tenelanda-Osorio et al. 2022), in this case with the higher temperature reducing the diversity of the volatile organic compounds formed. Experiments directly relevant to the surface conditions on Jovian moons have mostly focused on inorganic products (Moore & Hudson 2000;Carlson et al. 2002;Loeffler et al. 2006Loeffler et al. , 2011Hand & Carlson 2015;Poston et al. 2017;Thomas et al. 2017;Davis et al. 2021;Li et al. 2022;Mifsud et al. 2022) or the destruction rate of possible biomarkers (Nordheim et al. 2018;Freissinet et al. 2019). One study investigated the formation of organic matter based on simple organic compounds in a water-ice matrix in conditions relevant to Europa (Hand & Carlson 2012). ...
We performed experiments of implantation of energetic sulfur ions (105 keV) into 2:1 water:propane ices at 80 K and analyzed the resulting refractory organic matter with ultrahigh-resolution mass spectrometry. Our goal was to characterize the organic matter processed in the surface conditions of Europa, where it would receive a heavy flux of energetic particles, including sulfur ions, and determine whether organosulfurs could be formed in these conditions, using the simplest alkane that can exist in solid form on Europa’s surface. We find that the produced organic matter contains a large variety of both aliphatic and aromatic compounds (several thousand unique formulae), including polycyclic aromatic hydrocarbons (PAHs), with masses up to 900 amu. A large number of aromatic hydrocarbons is found along with oxygenated, mostly aliphatic, compounds. Organosulfurs are found in both CHS and CHOS form, demonstrating they can be formed from any organic compound through sulfur implantation. These organosulfurs’ properties (aromaticity, mass) appear similar to the rest of the organic matter, albeit their low quantity does not allow for a thorough comparison. Our results have implications for the type of refractory organic matter that could be observed by the JUICE and Europa Clipper space missions and how the surface of Europa could generate complex organics, including PAHs and organosulfurs, that could then enrich the subsurface ocean. In particular, they indicate that a large diversity of organic matter, including organosulfurs, can be formed from simple precursors in a geologically short time frame under the ion flux that reaches Europa.
... 45), even with the modest H 2 O loss rates derived here, the radiolysis-driven erosion of the surface is comparable to, if not the dominant driver of, Europa's surface erosion and modification. These updated constraints also affect the preservation of potential biosignatures in Europa's near-surface ice layers 46 . ...
Jupiter’s moon Europa has a predominantly water-ice surface that is modified by exposure to its space environment. Charged particles break molecular bonds in surface ice, thus dissociating the water to ultimately produce H2 and O2, which provides a potential oxygenation mechanism for Europa’s subsurface ocean. These species are understood to form Europa’s primary atmospheric constituents. Although remote observations provide important global constraints on Europa’s atmosphere, the molecular O2 abundance has been inferred from atomic O emissions. Europa’s atmospheric composition had never been directly sampled and model-derived oxygen production estimates ranged over several orders of magnitude. Here, we report direct observations of H2⁺ and O2⁺ pickup ions from the dissociation of Europa’s water-ice surface and confirm these species are primary atmospheric constituents. In contrast to expectations, we find the H2 neutral atmosphere is dominated by a non-thermal, escaping population. We find 12 ± 6 kg s⁻¹ (2.2 ± 1.2 × 10²⁶ s⁻¹) O2 are produced within Europa’s surface, less than previously thought, with a narrower range to support habitability in Europa’s ocean. This process is found to be Europa’s dominant exogenic surface erosion mechanism over meteoroid bombardment.
... As hypothesized markers of plumes (Quick & Hedman, 2020), the low-albedo deposits that flank several double ridges could be investigated for changes in radii and albedo since Juno, providing clues as to whether plume activity (if present) is ongoing, has lessened, or increased. Given the potential for fresh plume deposits to contain preserved biomarkers (Nordheim et al., 2018;Quick & Hedman, 2020), such observations would ideally be coupled with spectral data to investigate the composition of any recently erupted brines. ...
On 29 September 2022 Juno's low‐light sensitive Stellar Reference Unit (SRU) captured a high‐resolution (256–340 m/pixel) broadband (450–1,100 nm) visible image of Europa's icy surface during the first close flyby of the Jovian moon since Galileo's last encounter in 2000. Collected at a sub‐spacecraft altitude of 412 km while the surface was illuminated only by Jupiter‐shine (incidence angle: 48–51°), the SRU image reveals a 3 × 10⁴ km² region between ∼0°–6°N and 43.5°–51°W in remarkable detail at the highest resolution to date. Prior coverage by Galileo under high‐sun conditions at 1 km resolution led to the characterization of the terrain as ridged plains with undifferentiated linea. The SRU image reveals a much richer and more complex picture. Intricate networks of cross‐cutting ridges and lineated bands surround an intriguing 37 km (east‐west) by 67 km (north‐south) chaos feature with a concentric fracture system, depressed matrix margins, and low‐albedo materials potentially associated with brine infiltration. The morphology and local relief of the chaos feature are consistent with formation in the collapse of ice overlying a salt‐rich lens of subsurface water. Low‐albedo deposits, similar to features previously associated with hypothesized cryovolcanic plume activity, flank nearby ridges. The SRU's high‐resolution view of many types of features in a single image allows us to explore their regional context and greatly improve the geologic mapping of this part of Europa's surface. The image reveals several relatively youthful features in a potentially dynamic region, providing baselines for candidate locations that future missions can investigate for present day surface activity.
... At the higher-albedo icy moons of Jupiter and Saturn, UV penetration has been discussed in the literature as being significantly deeper than at Mars and Ceres, perhaps even up to 1 m for simulations of ice blocks 22 . At Europa, the limiting effect on survival of organics is the charged particle radiation environment 33 . However, in the saturnian system, the opposite is true: solar UV fluxes are significantly higher than magnetospheric particle fluxes 34,35 because neutral particles dominate over charged particles in the Saturn system, a result of plume activity at Enceladus 36 39 were used by to estimate timescales of survival of amino acids at Enceladus 9 . ...
The saturnian moon Enceladus presents a remarkable opportunity in our solar system for searching for evidence of life, given its habitable ocean and plume that deposits organic-bearing ocean material onto the surface. Organic ocean material could be sampled by a lander mission at Enceladus. It is of interest to understand the amount of relatively pristine, unaltered organics present on the surface, given the ultraviolet (UV) and plasma environment. Here, we investigate UV penetration into Enceladus’s surface and the resultant effective exposure ages for various regions, using the UV reflectance spectrum of Enceladus as measured by the Hubble Space Telescope and considering the rate of resurfacing by plume fallout. In high plume fallout regions near the south pole, plume grains are buried by fresher grains within years, resulting in low levels of exposure to solar UV, which penetrates only ~100 micrometers. Regions at latitudes south of ~40°S can have exposure ages <100 years, translating to relatively high abundances of pristine organic material preserved in the regolith.
... The most complete method to compute particle precipitation is to follow individual particle trajectories. Paranicas et al. (2001Paranicas et al. ( , 2007 and Nordheim et al. (2018) used the facts of small electron gyroradius and rapid bounce to estimate the precipitation patterns on Europa. This oversimplifies the particle motion and any effects due to a finite gyroradius would likely be missed. ...
... These energetic charged particles bombard Europa's surface in a highly non-uniform fashion, and attempts have been made to predict their weathering pattern (Pospieszalska and Johnson 1989;Paranicas et al. 2001;Addison et al. 2021). Energetic electrons represent the largest contribution to the surface radiation (Paranicas et al. 2007) and are expected to bombard the surface in a lens-like pattern centered on the lowlatitude trailing hemisphere and leading hemispheres (Paranicas et al. 2001;Truscott et al. 2011;Patterson et al. 2012;Nordheim et al. 2018). This expected bombardment pattern appears to roughly correlate with the presence of an unknown hydrated species (possibly H 2 SO 4 ) on the trailing hemisphere (Paranicas et al. 2001;Carlson et al. 2005;Grundy et al. 2007;Brown and Hand 2013;Fischer et al. 2015Fischer et al. , 2016Ligier et al. 2016), meaning that electrons may add energy that allows the sulfur originated from Io to form hydrated sulfuric acid. ...
We present an overview of the radiation environment monitoring program planned for the Europa Clipper mission. The harsh radiation environment of Jupiter will be measured by a dedicated Radiation Monitor (RadMon) subsystem, yielding mission accumulative Total Ionizing Dose (TID) and instantaneous electron flux measurements with a 1-Hz cadence. The radiation monitoring subsystem is comprised of a stand alone sensor assembly along with distributed TID assemblies at various locations on the spacecraft. The sensor assembly itself is made of a TID sensor stack using the Metal-Oxide Semiconducting Field-Effect Transistor (MOSFET) and a Charge Rate Monitor (CRM) that uses a stack of bulk charge collection plates. The TID measurements will provide the critical information about the overall radiation levels relevant to the degradation of electronics over time, and the electron flux data can serve as a proxy for the Internal ElectroStatic Discharge (IESD) environment by measuring the >∼1 MeV electron environment. In addition, the radiation monitoring subsystem data will be augmented by serendipitous radiation data from science instruments onboard. This will be enabled by careful modeling and analysis of opportunistic background data from potentially the following instruments: Europa Imaging System (EIS), Europa-Ultraviolet Spectrograph (Europa-UVS), Mapping Imaging Spectrometer for Europa (MISE), MAss Spectrometer for Planetary EXploration (MASPEX), Plasma Instrument for Magnetic Sounding (PIMS), and SUrface Dust Analyzer (SUDA). Based on the current analysis, these instruments will be most sensitive to >1 MeV electrons. As such, the high-energy electron data obtained by the radiation monitoring subsystem will be qualitatively and quantitatively enhanced by the high-energy electron data acquired by the instruments. The holistic radiation monitoring program for the mission will be an extensive collaboration among many teams across the flight and payload systems.
Although the radiation monitoring subsystem itself is an engineering resource for the mission, the collective data from the mission can also be used to improve the scientific understanding of the Jovian magnetosphere and the high-energy electron environment near Europa, where the motion of charged particles is perturbed by the local electromagnetic environment. The data could also help in the understanding of the radiation modification of Europa surface compounds, which could subsequently help guide lab experiments to aid in understanding the origin and evolution of surface materials and in constraining the interpretation of observational data. To this end, the radiation monitoring subsystem is a useful resource for helping address the Europa Clipper mission’s primary goal of assessing the habitability of Europa.
... Finally, the precise estimation of an age is fundamental for a proxy to be useful, and it remains very difficult to date smectitic clay minerals other than relying on certain impurities (transition ions) and point defects (radicals) which may be probed using electron paramagnetic resonance spectroscopy (Allard et al., 2012;Balan et al., 2020). Still, there is no doubt that the results of the present study will be of great help to constrain better the geochemical conditions existing or having existed on extraterrestrial planetary bodies such as Mars, on which the production of clay minerals has been intense (Carter et al., 2013;Ehlmann & Edwards, 2014), or on rocky and/or icy small bodies such as Ceres, Enceladus, or Europa on which the production of (probably smectitic) clay minerals have recently been reported (Marchi et al., 2019;Nordheim et al., 2018;Waite et al., 2017). ...
Smectitic clay minerals are unique indicators of paleoenvironmental conditions and exhibit a unique reactivity in the mineral world. Smectites may exhibit tetrahedral substitutions (Al3+, and sometimes Fe3+, can substitute for Si4+ in tetrahedral sites), resulting in a layer-charge increase, thereby impacting their properties (e.g. swelling and sorption capacities, catalytic properties, expandable abilities). The objective of the present study was to determine the influence of pH conditions on the hydrothermal production of smectite end-members exhibiting tetrahedral Al substitutions (saponite, beidellite, and nontronite), using X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) methods. The results of a series of syntheses conducted at various pH values allowed discussion of the crystallization pathways of these smectites from a mechanistic point of view. Altogether, the present study provided easily reproducible protocols for the hydrothermal production of pure saponite, nontronite, or beidellite (i.e. with no other mineral). The successful synthesis of pure saponite was achieved by exposing the starting gels to 230°C for 4 days in solutions at pH ranging from 5.5 to 14. The successful synthesis of pure beidellite was achieved by exposing the starting gels to 230°C for 9 days in a solution at pH 12. The successful synthesis of pure nontronite was achieved by exposing the starting gels to 150°C for 2.5 days in a solution at pH 12.5. Although extrapolating experimental results to natural settings remains difficult, the results of the present study may be of great help to constrain better the geochemical conditions existing or having existed on extraterrestrial planetary bodies.
... The study of Cooper et al. (2001) estimated that electrons contribute 75% of the total energy deposited by particle impacts into the moon's surface. Electrons also penetrate more than 50 times deeper into Europa's icy surface than ions (e.g., Teolis et al., 2017;Ziegler & Manoyan, 1988), and as such are important agents in modifying the optical properties observed by telescopes and spacecraft, as well as in the destruction of potential biosignatures (Nordheim et al., 2018). Recent laboratory studies of electron sputtering yields from water ice (e.g., Galli et al., 2018;Meier & Loeffler, 2020) have enabled the first estimates of global sputtering rates across Europa's entire surface from magnetospheric electron impacts (Davis et al., 2021;. ...
... Therefore, Paranicas et al. (2001) concluded that energetic electrons are a principal agent of radiolytic surface chemistry on Europa. The model of Paranicas et al. (2001) was also applied in the studies of Patterson et al. (2012), Dalton et al. (2013), and Nordheim et al. (2018) to investigate various surface modification processes at Europa. ...
... Dalton et al. (2013) hypothesized that electron bombardment locally "heats" the surface, allowing magnetospheric sulfur ions to implant more deeply and create the observed sulfuric acid patterns. The studies of Paranicas et al. (2001), Patterson et al. (2012), Dalton et al. (2013), and Nordheim et al. (2018) all considered electron dynamics in spatially and temporally uniform electromagnetic fields near Europa, that is, without the inclusion of the moon's induced field or plasma interaction effects. Truscott et al. (2011) modeled energetic electron trajectories and irradiation of Europa's surface while including the moon's induced field for the conditions of the Galileo E4 flyby, though these authors did not draw conclusions on the influence of the induced field on their electron surface flux patterns. ...
We calculate the time‐varying spatial distribution of energetic magnetospheric electron influx onto Europa's surface by combining a hybrid model of the moon's draped electromagnetic environment with a relativistic particle tracer. We generate maps of the energetic electron influx patterns at four distinct locations of Europa relative to the center of the Jovian magnetospheric current sheet. For a full synodic rotation of Jupiter, these results are applied to constrain the averaged number and energy influx patterns as well as the O2 sputtering rates associated with energetic electron precipitation. We also determine the relative contributions of magnetospheric ions and electrons to surface erosion and exospheric genesis at Europa. Our major results are: (a) Except for a small region near Europa's downstream apex, the moon's entire surface is exposed to heavy irradiation by magnetospheric electrons. (b) The spatial distribution of energetic electron influx onto Europa's surface is only slightly modified by field line draping and the induced magnetic field from the moon's subsurface ocean. (c) The contributions of magnetospheric electron and ion impacts to energy deposition onto Europa's surface are of the same order of magnitude. (d) Within uncertainties, impinging magnetospheric electrons and ions make similar contributions to O2 sputtering from Europa's surface. (e) The spatial distribution of electron energy influx and the observed concentrations of sulfuric acid (H2SO4) are only weakly correlated, suggesting that energy deposition by magnetospheric electron impacts is not a necessary agent for H2SO4 production within Europa's surface.
... Sparse observations and simulations have shown that wave-particle interactions near Io [e.g., 35,57] can locally pitch angle scatter ions into the atmospheric loss cone. Moons can also directly absorb charged particles, which in turn also weather the moons' surfaces, but the efficiency of the process is dependent on where the moon is located at any given time as well as the pitch angle distributions of electron and ions [e.g., 58,59]. Therefore, material-laden magnetospheres such as Jupiter's provide us with a natural laboratory to probe competing processes acting both as sources and sinks. ...
... As can be seen in Fig. 29.6, however, radiation rapidly decreases with depth. Nordheim et al. (2018) analyzed the dose for energetic particles for various depths of water and different locations on Europa in the context of potential biosignatures. While the dose at the surface is in the range of 100 kGy d (equal to 10000 krad/d), this enormous value decreases by about eight orders of magnitude below 1 m of water/ice. ...
... Since the magnetic moment of Saturn is about 60 times smaller than that of Jupiter, radiation at Enceladus is a less severe problem than at Europa. On the surface of Enceladus, the radiation dose is about three orders of magnitude lower than on Europa (derived from Nordheim et al. 2018). While there is some literature on the scientific aspects of the radiation environment at the icy moons, there is considerably less available literature on the engineering implications. ...
The exploration of icy environments in the solar system, such as the poles of Mars and the icy moons (a.k.a. ocean worlds), is a key aspect for understanding their astrobiological potential as well as for extraterrestrial resource inspection. On these worlds, ice melting probes are considered to be well suited for the robotic clean execution of such missions. In this chapter, we describe ice melting probes and their applications, the physics of ice melting and how the melting behavior can be modeled and simulated numerically, the challenges for ice melting, and the required key technologies to deal with those challenges. We also give an overview of existing ice melting probes and report some results and lessons learned from laboratory and field tests.KeywordsIce melting probeIce penetrationIcy moonsOcean worldsMarsExploration
... Past studies on loss processes were often based on observing losses during close moon flybys, observing particles within loss cones, and calculating precipitation based on wave observations. These methods have the disadvantage that they are working locally in time and space, while not all particles in the geometric path of the moon precipitate onto it, particularly for moons with faint ionospheres (e.g., Nordheim et al., 2018;Roussos et al., 2012). Some moons may completely clear out their orbits, meaning that there is no steady state precipitation anymore. ...
