The search for extraterrestrial life is a major driver of current space exploration, requiring sensitive instrumentation and a thorough understanding of biosignature preservation. Studying terrestrial analogs provides insights into the types of biosignatures preserved in early terrestrial rocks at a period when life may have flourished at the surface of Mars. Here, we investigate the 3.33 Ga Josefsdal Chert from the Barberton Greenstone Belt, South Africa, a carbonaceous chert containing presumed traces of early life, using laser ablation ionization mass spectrometry (LIMS). Chemical analyses were carried out with both a high-resolution laboratory instrument and a compact space-prototype, designed for the in situ chemical composition analysis of solids on solar system objects. LIMS was used to characterize the element composition and its spatial distribution in carbonaceous laminations and clots. These were previously identified by optical microscopy and Raman spectroscopic mapping and considered to be potential biosignatures. LIMS found these features to be enriched in biorelevant elements, such as CHNOPS as well as biologically important transition metals, thus supporting a biogenic origin of the studied organic material of the Josefsdal Chert. The combined approach of the two instruments strengthens confidence in the results and demonstrates the potential of LIMS for future space exploration and sample return missions and the in situ identification of biosignatures.
Ballistic sedimentation, the process by which impact-generated ejecta is deposited and interacts with planetary surfaces, remains understudied despite its significant role in landscape evolution on cratered terrain across the solar system. We investigated the dynamical and geomorphological effects of ejecta emplacement under three different gravitational accelerations, focusing on how gravity influences the runout, erosion, and subsurface regolith shear characteristics of ballistic erosion and sedimentation. Building on previous ground-based experiments utilizing a meter-scale lever-arm catapult to simulate ejecta emplacement, we extend these studies by deploying a subscaled catapult on reduced-gravity parabolic flights aboard a modified Boeing 727–200. These experiments recreated lunar and Mercurian/Martian gravity conditions, allowing direct observation of ejecta–regolith interactions in reduced gravity. Our ejecta deposition results are consistent with nondimensional scaling relationships established for cratering experiments; they demonstrate gravity-independent ejecta runout lengths; and the results show gravity-dependent runout efficiency. Related experimental results show a logarithmic shear profile in the regolith bed beneath ejecta, similar to that predicted from fluid mechanics. We also explore a potential relation between ejecta emplacement and landslide runouts, highlighting areas of commonality and differences, and apply our results to case studies involving ejecta from Linné Crater on the Moon and the Ries Crater in Germany. This work provides an interpretive framework for future experimental, theoretical, observational, and field studies in cratering and landslide geology while highlighting areas for future research.
The implantation of solar wind (SW) and Earth’s magnetospheric protons is recognized as a primary source of hydrogen (H) in the top 100 nm of the lunar regolith. The effective proton flux reaching the lunar surface, however, gets modified by the plasma environment. We present a framework for H implantation that considers this sheath-modified proton flux. Our simulation indicates that a plasma sheath enhances H implantation during dawn and dusk, resulting in higher nighttime retention than in previous studies. Further simulation using the Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon’s Interaction with the Sun (ARTEMIS) measurements suggests that H implantation occurs continuously on the Moon throughout its orbit, either from SW or from Earth’s wind protons. A farside-nearside hemispherical asymmetry in H implantation is observed from the combined effects of the Moon’s tidal locking with Earth, periodic passage through Earth’s magnetosphere, and temperature-dependent thermal diffusion. The present analysis may have important implications for constraining the retrieval of relevant parameters from remote sensing observations.
Earth, and potentially Venus, formed through giant impacts involving early-formed planetesimals and planetary embryos in the inner solar system, but the size distribution of these bodies remains poorly constrained. Angrites sample one of the earliest differentiated bodies in the inner solar system and preserve a marked redox contrast with HEDs: evolved angrites record oxygen fugacity ( f O _2 ) near-iron-wüstite (IW) or slightly supra-IW conditions, whereas HEDs are ∼1–2 log units more reduced. This difference has been interpreted to indicate a comparatively oxidized mantle for an angrite parent body (APB), but most f O _2 estimates are derived from evolved magmas that may not track deep-mantle conditions. Here, we explore whether internal magma self-oxidation driven by Fe ^3+ stabilization in a deep magma ocean followed by fractional crystallization can account for the redox state of evolved angrites and what this implies for APB size. We combine parameterizations of Fe ^3+ /ΣFe in silicate melts with fractional crystallization models of Group 1–2 angrites, starting from metal-saturated conditions consistent with primitive angrites. We find that magma self-oxidation reproduces the f O _2 inferred for evolved angrites only if core–mantle equilibration pressures exceed several gigapascals. Such pressures imply a body substantially larger than asteroid Vesta. For plausible APB compositions and starting redox states, radii of ∼1250–2500 km are required, comparable to or exceeding the size of the Moon and overlapping independent geobarometric estimates. Rather than uniquely determining APB size, our results provide a redox-based lower bound on its size and demonstrate that internal oxidation offers a viable mechanism for generating oxidized signatures in evolved angrites.
It is demonstrated that there should be a local ion and magnetic perturbation associated with Starship landings. These space plasma perturbations result from the photoionization of the outgassed water vapor from the surface ice created by the Starship ejecta plume during landing. For a landing at 89° latitude at 8.5 hr local time, the newly created ions from the outgassing vapor cloud are accelerated by the solar wind electric field to form electric currents having a density exceeding 10 ^−7 A m ^−2 . Within 100 km of the landing site, the strength of the magnetic perturbation from these currents can be on the order of ∼1–2 nT for such a polar morning landing. Space plasma instruments like magnetometers and ion spectrometers would be capable of measuring such effects from the human-created water vapor cloud.
Phase diagrams with newly discovered supercritical (SC) solid-like state, liquid/liquid-like boundary, and Dwij point, beyond which only gas and solid exist (V. Prasad et al.), can provide new insights into many terrestrial and extraterrestrial phenomena. This is demonstrated here for Earth’s interior and for five other planets. For example: (a) Pure water would transition from liquid to an SC liquid-like state within ∼15 km, to solid-like in the upper mantle (∼60 km) continuing to the lower mantle, and finally, as fcc-solid at ∼1000 km. (b) SC water for heat recovery may be available within 2–5 km depths. (c) Methane/natural gas becomes SC gas-like at ∼0.16 km, remains SC liquid-like up to ∼7 km (12 times higher density), and becomes SC solid-like below, indicating more reservoir gas than previously known. (d) Regarding CO _2 sequestration at the ocean bottom, its density being only 4% higher than water at 3700 m presents major challenges. (e) If SC CO _2 is injected for enhanced natural gas recovery, it would go down as SC liquid-like to ∼8.6 km, and then, become solid-like: a better condition for storage. (f) It is impossible for pure hydrogen to exist inside the Earth. (g) Only gaseous and solid CO _2 can exist on Venus. (h) Helium in the shallow layer of the Moon may exist in its SC state. (i) On Jupiter and Saturn, hydrogen and helium are mostly in an SC gas-like state. (j) If water exists on Mars, it would transition from compressed liquid on the surface to SC solid-like at 310 km.
Unlike many other natural disasters, an impact by an asteroid on Earth may be preventable. One method available to stop an impact is the use of a nuclear explosive device (NED), through either deflection via surface ablation or intentional robust disruption such that no fragment poses a risk to the planet. To simulate NED mitigation missions, we implemented an X-ray energy deposition model in the smoothed particle hydrodynamics (SPH) code Spheral. To assess our SPH results, we first compared with previous 1D (planar) and 2D (cylindrical) mesh-based asteroid deflection results. 1D Spheral simulations agree with these prior models to within 0.8% across a range of X-ray fluences, illumination times, blackbody temperatures, asteroid compositions, and porosities. Full 3D models in Spheral agree to within ∼18.1% with the prior cylindrical simulations but are limited to coarser resolution owing to the computational requirements of modeling in full 3D versus the finer resolutions practical in reduced 2D models. We present intentional disruption simulations in 3D for a homogeneous, 160 m asteroid composed of forsterite, exploring how disruption varies both with the NED height of burst (distance from the asteroid surface) and with damage model parameter choices. These simulations explore the near-threshold parameter space below the mission-design heuristic boundary for definitive robust disruption. Definitive verification against common robust disruption metrics, including fragment size criteria, would require running simulations to significantly longer run times. However, the observed damage extent and bidirectional material motion at the final simulated times strongly suggest that these cases lie near the robust disruption regime.
Mare Australe on the Moon features a peculiar style of basalt emplacement, where volcanism occurs in small patches arranged in a circular pattern, not confined to an established impact basin. In this study, for the first time, we carried out a detailed mineralogical investigation of the Australe region, assessing both nonmare and mare units using Moon Mineralogy Mapper (M ^3 ) to understand its geological evolution. The widespread distribution of orthopyroxene encircling Mare Australe supports the presence of the Australe Basin, previously undetected by gravity and topographic datasets. Further, the orthopyroxene distribution is consistent with the boundary of the GRAIL-discovered Australe North Basin, suggesting a dual impact scenario in the region. Our results reveal the presence of basalts dominated by low-to-intermediate-Ca pyroxenes, compositionally distinct from typical high-Ca-pyroxene-bearing lunar basalts. The study showcases that remote sensing-based mineralogical investigations provide critical evidence for tracing ancient, now obliterated basins on the Moon.
The continuous discovery of exoplanets, each with distinctive stellar and planetary properties, along with the development of higher resolution ground and space telescopes has positioned climate evolution as a fundamental component of the study of habitability. In particular, the planet Gl 514 b, located within the habitable zone of an M0.5 dwarf star 7.62 pc from Earth, is a candidate for direct observations with future ground and space-based telescopes and therefore worthy of climate modeling. One notable aspect of this planet is its eccentricity of e = 0.45^+0.15_-0.14, which could affect the seasonal climate by inducing large swings in instellation over the course of an orbit. Hence, we simulate a plausible range of climates on this planet to assess the likelihood that its surface is habitable as well as estimate the surface ice coverage, which could affect the photometric signal. To perform these simulations, we use an energy balance model to explore the parameter space permitted by the observations and the allowed ranges of the obliquity, eccentricity, atmospheric CO_2, precession angle, land fraction, and land distribution. We find the planet is most likely to be in either a snowball or ice free state, but about 1.27
We investigate methods of generating image subtraction templates that are suitable for slow-moving object searches with data from NASA’s TESS mission. We develop a novel “donut” template that is well suited to Centaurs and trans-Neptunian objects; compared to a template constructed from the median of all images, a donut template substantially increases the detectability of these objects for rates of motion <2″ hr ^−1 . This cleaning method brings the background noise level down to <1 electron per second, revealing both slow-moving trans-Neptunian objects as well as diffuse comet tails. This cleaning method is also well suited for preparing images for shift-and-stack processing.
Models of our solar system’s protoplanetary disk account for processes such as the infall of water–ice-rich grains from the surrounding molecular cloud, the reprocessing of some infalling water–ice in the hot inner disk, and water’s outward migration in the disk. These models predict deuterium abundance in water as a function of heliocentric distance. The James Webb Space Telescope (JWST) enables us to test these models by measuring the abundance of deuterium on icy outer solar system bodies through spectroscopic observations of the semiheavy water (HDO) band near 4.1 μ m. However, a hurdle to measuring deuterium abundances from JWST spectra is the lack of optical constants for HDO. We present the separated contributions of HDO and H _2 O to the optical constants of crystalline water–ice that contains both isotopologues. In addition, we combine these effective optical constants, a radiative transfer model, and a JWST spectrum of the Uranian satellite Titania to measure its deuterium abundance in water, finding D/(H+D) = (2.8 ± 0.5) × 10 ^−4 in agreement with the model by L. Yang et al. Using a simple model, we estimate that most of Titania’s water originated from thermally processed inner-disk water, and only a minor portion came from inherited molecular-cloud water. By combining our Titania measurement with Saturnian satellite and comet measurements in the literature, we suggest that outer-satellite water came from a more homogeneous reservoir than comets, and perhaps accreted over a shorter time interval than comets. Furthermore, Titania’s deuterium abundance suggests that it formed in a lower-temperature, hydrogen-poor circumplanetary disk rather than a higher-temperature, hydrogen-rich disk.
Polarimetric L -band synthetic aperture radar (SAR) has been proposed as a tool to detect and map shallow (<10 m) subsurface water-ice in the midlatitudes of Mars, a major science target and critical resource for future human exploration. In this study, we implement a radar backscatter forward model to assess the geophysical conditions under which such a system can identify and characterize shallow ice. The model combines shooting-and-bouncing ray physics, electric-field Monte Carlo integration, and the coherent backscatter opposition effect via time-reversed ray pairs to simulate backscattering from complex, diffusive, multilayer substrates. We produce polarimetric responses in both sounder and side-looking orientations, from which the Stokes parameters ( S _1–4 ) are used to derive the circular polarization ratio (CPR) and degree of polarization ( m ), forming a consistent set of observables. Results show ice-rich media exhibit high volumetric scattering, an enhancement of CPR, and a slow decay in radar echo power with round-trip delay, defining an “ice-like signature” that is useful for detecting shallow ice. We present a catalogue of 15 scenarios, with a variety of regolith and ice layer thicknesses, and two different scatterer inclusion fractions. We further explore two additional radar frequencies (very high frequency and the P band) in sounder mode and discuss what combination of sensors can offer the most comprehensive characterization of the subsurface. The chosen scenarios act as a reference for understanding scattering physics within a varied, ice-bearing subsurface. This work demonstrates the capability of identifying and differentiating subsurface ice with an L -band compact polarimetric SAR payload.
Only three binaries have been identified among the Centaur population. Because their perihelia are significantly closer than those of other trans-Neptunian binaries (TNBs), these systems allow a detailed look at tight binaries in the broader TNO population and provide critical insight into the disruption of binaries as they enter the Centaur population. Using recent and archival Hubble Space Telescope (HST) observations, along with Keck data, we present a spin-orbit study of Typhon-Echidna. We find that the binary's mutual orbit is inconsistent with a Keplerian orbit; more detailed non-Keplerian fits show that the mutual orbit is rapidly precessing. We measure Typhon's dynamical oblateness, J_2, at ∼10σ confidence and find that Typhon's rotation pole is ≳20^∘ misaligned with the binary's mutual orbit. Assuming Typhon has a triaxial shape, our results, combined with rotational light curves and thermal measurements from the literature, suggest ellipsoidal semi-axes of a=93^+8_-6 km, b=84^+6_-6 km, and c=65^+9_-8 km. We further investigate the observational consequences of the complex spin-orbit dynamics, including light curve alteration by axial precession of Typhon and substantial changes to the system's mutual event season. Based on the system's dynamically excited state, we suggest a recent encounter with a giant planet may have substantially altered the system, potentially consistent with a binary in an early stage of disruption. This hypothesis can be tested with resolved photometric observations of the system. Our investigation highlights how non-Keplerian dynamics enhances our understanding of TNB systems and motivates ongoing observations of TNBs with astrometry, photometry, and stellar occultations.
We present maps of H2O, CO2, and a 4.57 um spectral feature across Callisto's surface observed using the James Webb Space Telescope (JWST). H2O ice was mapped by measuring band parameters of the 3.1 um Fresnel peak across the leading and trailing hemispheres under a simplified assumption of crystalline ice. We update the CO2 solid-phase, CO2 gas, and 4.57 um feature band depth maps originally presented in Cartwright et al. (2024) with a new JWST observation of Callisto centered on Valhalla, the largest multi-ring impact basin in the solar system. Our H2O ice map shows that the Fresnel peak on the trailing hemisphere exhibits a bullseye pattern that is weaker at low latitudes, and on the leading hemisphere its strength is associated with impacts. This dichotomy is possibly related to the Jovian magnetospheric plasma impinging on the trailing hemisphere. Our solid-phase CO2 map reveals an enhancement in the vicinity of the Lofn/Heimdall impact craters, a region that may be the largest reservoir of non-radiolytic CO2 on Callisto's surface. The gas-phase CO2 exhibits a patchy spatial distribution and does not clearly correlate with solid CO2.
Abstract The interstellar comet 2I/Borisov is the first interstellar object where compositional characterisation was possible throughout its entire perihelion passage. We report all 16 epochs of a comprehensive optical observation campaign with ESO Very Large Telescope’s integral field spectrograph MUSE, spanning 126 days from 2019 November 14 to 2020 March 19. The spatial dust emission of 2I/Borisov was predominantly smooth, with no seasonal effect. A jetlike feature was consistently visible. The gas production morphology of its coma was also smooth and similar for C 2 , NH 2 , and CN: symmetric around the optocentre. The production rates of these species gently declined into and beyond perihelion, until 2I’s outburst and splitting event in early 2020 March. C 2 , NH 2 , and CN production rates all increased, with NH 2 being the most significant; the dust emission also slightly reddened. 2I/Borisov is a carbon-depleted, relatively NH 2 -rich comet when compared to those comets yet measured in the solar system.
Abstract The detection of CO 2 on the Jovian satellite Europa by Galileo/NIMS and recent mapping of the leading side by JWST has revealed that it is most concentrated in geologically young terrains, and its ν 3 asymmetric stretch appears as a spectral doublet centered at 4.25 and 4.27 μ m. Since crystalline CO 2 is unstable at Europan surface conditions, this observation implies an active source and a trapping medium, which may be separate. To this end, several hypotheses have been proposed, but no laboratory work has successfully reproduced the spectral features of CO 2 on Europa so far. Radiolyzed carbonates have also been discussed as plausible precursors and host materials for CO 2 , though their role has not been experimentally validated in a Europa-like environment. Here, we report the first laboratory experiments investigating CO 2 production from carbonate salts exposed to 10 keV electron irradiation at 50, 100, and 120 K in ultrahigh vacuum. Using diffuse reflectance FTIR spectroscopy, we observe the emergence, growth, and saturation of an absorption doublet centered near 4.25 and 4.27 μ m, consistent with the CO 2 ν 3 band. Postirradiation thermal desorption studies using residual gas analysis reveal that the radiolytically formed CO 2 is stable at temperatures beyond Europa’s surface. This work provides the first experimental evidence that low-energy electron irradiation of carbonates in cryogenic, vacuum conditions can produce and retain CO 2 , and suggests that carbonates can serve as endogenous reservoirs of CO 2 on irradiated icy bodies in the outer solar system.
Abstract We report a survey of molecular emission from cometary volatiles using the Atacama Large Millimeter/submillimeter Array toward comet C/2017 K2 (PanSTARRS) carried out on UT 2022 September 21, 22, and 23 at a heliocentric distance ( r H ) of 2.1 au. These measurements of HCN, CS, CO, CH 3 OH, and H 2 CO (along with continuum emission from dust) sampled molecular chemistry in C/2017 K2 at the inner edge of the H 2 O sublimation zone, the region from r H = 2 to 3 au where H 2 O begins vigorously subliming and increasingly dominating comet activity, discerning parent from daughter or extended source species. This work presents spectrally integrated flux maps, production rates, and parent scale lengths for each molecule. CH 3 OH, CO, and HCN were produced within ∼250 km of the nucleus, potentially including contributions from sublimation of icy grains. CS was consistent with production from CS 2 photolysis, and H 2 CO required production from extended sources in the coma. An ortho-to-para ratio of 2.9 ± 0.4 for H 2 CO was derived from simultaneously measured transitions of each spin species. The continuum was extended and spatially resolved, consistent with thermal emission from dust in the coma. Analysis of the continuum visibilities provided an upper limit on the nucleus diameter d < 6.6 km and coma dust masses of (1.2–2.4) × 10 11 kg.
Abstract The enrichment of heavy isotopes of volatile elements in the Martian atmosphere indicates that Mars lost a large portion of its atmosphere through escape to space. Recent atmospheric measurements by the ExoMars Trace Gas Orbiter (TGO) have suggested that the vertical profiles of oxygen isotopic compositions are influenced by chemical reactions involving isotopic fractionation. However, their quantitative impacts have not yet been fully evaluated. In this study, we develop a 1D photochemical model that incorporates oxygen isotopic fractionation associated with CO 2 photolysis and O 3 formation to investigate the vertical profiles of oxygen isotopic compositions. Our calculations show that CO is depleted in heavy oxygen isotopes relative to CO 2 , reaching δ 18 O ∼ −25‰ and δ 17 O ∼ −15‰, primarily due to isotopic fractionation during CO 2 photolysis. The vertical profiles of oxygen and carbon isotopic compositions are in good agreement between our model and the TGO measurements. O 3 is strongly enriched in 18 O and 17 O, reaching δ 18 O ∼ 100‰ and δ 17 O ∼ 50‰ as a consequence of the isotopic fractionation during its formation, whereas atomic oxygen is highly depleted in the heavy oxygen isotopes with δ 18 O ≲ −100‰ and δ 17 O ≲ −50‰ so as to compensate for their enrichment in O 3 . These chemical fractionation processes can deplete the heavy oxygen isotopes in species that escape from the upper atmosphere and thereby enhance the isotopic fractionation associated with oxygen escape to space. Such fractionated isotopic compositions of escaping oxygen may be detectable by the Martian Moons eXploration (MMX) mission.
The enrichment of heavy isotopes of volatile elements in the Martian atmosphere indicates that Mars lost a large portion of its atmosphere through escape to space. Recent atmospheric measurements by the ExoMars Trace Gas Orbiter (TGO) have suggested that the vertical profiles of oxygen isotopic compositions are influenced by chemical reactions involving isotopic fractionation. However, their quantitative impacts have not yet been fully evaluated. In this study, we develop a 1D photochemical model that incorporates oxygen isotopic fractionation associated with CO _2 photolysis and O _3 formation to investigate the vertical profiles of oxygen isotopic compositions. Our calculations show that CO is depleted in heavy oxygen isotopes relative to CO _2 , reaching δ ^18 O ∼ −25‰ and δ ^17 O ∼ −15‰, primarily due to isotopic fractionation during CO _2 photolysis. The vertical profiles of oxygen and carbon isotopic compositions are in good agreement between our model and the TGO measurements. O _3 is strongly enriched in ^18 O and ^17 O, reaching δ ^18 O ∼ 100‰ and δ ^17 O ∼ 50‰ as a consequence of the isotopic fractionation during its formation, whereas atomic oxygen is highly depleted in the heavy oxygen isotopes with δ ^18 O ≲ −100‰ and δ ^17 O ≲ −50‰ so as to compensate for their enrichment in O _3 . These chemical fractionation processes can deplete the heavy oxygen isotopes in species that escape from the upper atmosphere and thereby enhance the isotopic fractionation associated with oxygen escape to space. Such fractionated isotopic compositions of escaping oxygen may be detectable by the Martian Moons eXploration (MMX) mission.
