We present a publicly available, high-resolution, filled-parameter-space synthetic distribution of the plutinos, trans-Neptunian objects (TNOs) librating in the 3:2 mean-motion resonance with Neptune, with particular focus on the plutinos simultaneously Kozai librating. This synthetic distribution was built in preparation for results from the Large inclination Distant Objects (LiDO) survey, which pointed at locations on the sky where Kozai plutinos are predicted to come to pericenter and are thus most easily detected in magnitude-limited surveys. Although we do not expect the full stable parameter space presented here to be populated with real TNOs, it provides a useful starting point for comparison with Neptune migration simulations and debiased observational results. Our new stable parameter-space synthetic distribution of fictitious plutinos is consistent with previous works, and we build on past results by focusing on the behavior of Kozai plutinos over 4 Gyr integrations. We find that 95% of 4 Gyr stable Kozai plutinos remain in the same ω-libration island for the entire integration. This provides an interesting diagnostic opportunity: any asymmetry in the true number of 4 Gyr stable Kozai plutinos in the two ω-libration islands must be caused by the details of emplacement during giant planet migration. Through analysis of previously published Neptune migration models, we show that the intrinsic fraction of plutinos captured into Kozai depends on Neptune’s migration speed and mode. Combining the filled-parameter-space synthetic distribution with future migration simulations and the results of the carefully characterized LiDO survey will enable interpretation of the intrinsic orbital distribution of the Kozai and non-Kozai plutinos.
The American Astronomical Society (AAS), established in 1899 and based in Washington, DC, is the major organization of professional astronomers in North America. Its membership of about 7,000 individuals also includes physicists, mathematicians, geologists, engineers, and others whose research and educational interests lie within the broad spectrum of subjects comprising contemporary astronomy. The mission of the AAS is to enhance and share humanity's scientific understanding of the universe.
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The Planetary Science Journal is an open access journal devoted to recent developments, discoveries, and theories in planetary science. The journal welcomes all aspects of investigation of the solar system and other planetary systems.
- The following article is Open accessLiDO: Exploring the Stable Plutino Parameter Space
Samantha M. Lawler et al 2025 Planet. Sci. J. 6 100
- The following article is Open accessThrust Faulting and the Late-stage Contraction of the Moon
T. R. Watters et al 2026 Planet. Sci. J. 7 239
View article, Thrust Faulting and the Late-stage Contraction of the MoonPDF, Thrust Faulting and the Late-stage Contraction of the MoonDownload ePub, Thrust Faulting and the Late-stage Contraction of the MoonLunar Reconnaissance Orbiter Camera images have revealed thousands of young thrust fault scarps in the highlands and mare. These relatively small-scale faults are the expression of a period of late-stage lunar global contraction. Here we present the most comprehensive assessment of recent thrust faulting on the Moon and its implications for lunar radius change. Combining the estimate of the fractional areal strain of the highlands from the population of lobate thrust fault scarps with the fractional areal strain of the maria from the population of small mare ridge thrust faults, the total areal contractional strain is estimated to be ∼0.0048% to 0.0053%. This areal strain corresponds to a radial contraction of ∼42 to 46 m. Assuming a uniform rate of radius change over the last 400 Ma, the rate of change is estimated to be a maximum of ∼11 cm Ma−1. The fractional areal strain of the maria contributes little to the total radius change, thus the late-stage radius change is dominated by the highland thrust faults. The isotropic compressional stress induced by this amount of radial contraction is estimated to be ∼4 MPa, consistent with stress drop estimates from recorded shallow moonquakes. Inconsistency between thermal history models that predict much larger amounts of radial contraction and the absence of degraded, ancient highland fault scarps supports a nonmonotonic lunar thermal evolution, possibly due to the insulating effects of a thick, porous megaregolith. Alternatively, the presence of a strong elastic lithosphere may have inhibited thrust faulting until stresses reached a threshold level in the Copernican era.
- The following article is Open accessGlobal Distribution of Atmospheric Formaldehyde Deposition Correlated with Water Vapor on a Warm Early Mars
Shungo Koyama et al 2026 Planet. Sci. J. 7 223
View article, Global Distribution of Atmospheric Formaldehyde Deposition Correlated with Water Vapor on a Warm Early MarsPDF, Global Distribution of Atmospheric Formaldehyde Deposition Correlated with Water Vapor on a Warm Early MarsDownload ePub, Global Distribution of Atmospheric Formaldehyde Deposition Correlated with Water Vapor on a Warm Early MarsOn early Mars, transient warm periods during the late Noachian and early Hesperian were likely triggered by episodic inputs of reducing greenhouse gases, such as H2. In such a weakly reducing atmosphere, formaldehyde (H2CO), a precursor for the abiotic formation of sugars via the formose reaction, can be effectively produced. While this pathway is a candidate source for Martian organic matter, previous 1D photochemical modeling could not predict the spatial distribution of organic synthesis. In this study, we developed a lookup table of H2CO production based on key atmospheric variables using a photochemical model and coupled it with a global climate model. We calculated the global distribution of the atmospheric deposition fluxes of H2CO under a 2 bar CO2 atmosphere containing 6% H2 with obliquity of 40°. Our results reveal a strong positive correlation between atmospheric H2CO deposition and H2O vapor abundance, driven by both the enhanced photochemical production of H2CO through H2O photolysis and the efficient scavenging by precipitation in humid regions. Significant atmospheric deposition of H2CO is observed over water bodies, including the northern ocean. Furthermore, atmospheric deposition hotspots emerge around topographic highs, such as the Tharsis and Elysium mons, due to orographic precipitation. We suggest that basins adjacent to persistently humid regions, which likely experienced H2CO accumulation and subsequent organic synthesis, could be potential landing sites for future missions to investigate ancient chemical evolution and whether it led to the origin of life.
- The following article is Open accessRefining the Transit-timing and Photometric Analysis of TRAPPIST-1: Masses, Radii, Densities, Dynamics, and Ephemerides
Eric Agol et al 2021 Planet. Sci. J. 2 1
View article, Refining the Transit-timing and Photometric Analysis of TRAPPIST-1: Masses, Radii, Densities, Dynamics, and EphemeridesPDF, Refining the Transit-timing and Photometric Analysis of TRAPPIST-1: Masses, Radii, Densities, Dynamics, and EphemeridesDownload ePub, Refining the Transit-timing and Photometric Analysis of TRAPPIST-1: Masses, Radii, Densities, Dynamics, and EphemeridesWe have collected transit times for the TRAPPIST-1 system with the Spitzer Space Telescope over four years. We add to these ground-based, HST, and K2 transit-time measurements, and revisit an N-body dynamical analysis of the seven-planet system using our complete set of times from which we refine the mass ratios of the planets to the star. We next carry out a photodynamical analysis of the Spitzer light curves to derive the density of the host star and the planet densities. We find that all seven planets’ densities may be described with a single rocky mass–radius relation which is depleted in iron relative to Earth, with Fe 21 wt% versus 32 wt% for Earth, and otherwise Earth-like in composition. Alternatively, the planets may have an Earth-like composition but enhanced in light elements, such as a surface water layer or a core-free structure with oxidized iron in the mantle. We measure planet masses to a precision of 3%–5%, equivalent to a radial-velocity (RV) precision of 2.5 cm s−1, or two orders of magnitude more precise than current RV capabilities. We find the eccentricities of the planets are very small, the orbits are extremely coplanar, and the system is stable on 10 Myr timescales. We find evidence of infrequent timing outliers, which we cannot explain with an eighth planet; we instead account for the outliers using a robust likelihood function. We forecast JWST timing observations and speculate on possible implications of the planet densities for the formation, migration, and evolution of the planet system.
- The following article is Open accessUranus Orbiter and Probe: Mission Challenges and Concept Updates Since the Origins, Worlds, and Life Decadal Survey
Amy A. Simon et al 2026 Planet. Sci. J. 7 143
View article, Uranus Orbiter and Probe: Mission Challenges and Concept Updates Since the Origins, Worlds, and Life Decadal SurveyPDF, Uranus Orbiter and Probe: Mission Challenges and Concept Updates Since the Origins, Worlds, and Life Decadal SurveyDownload ePub, Uranus Orbiter and Probe: Mission Challenges and Concept Updates Since the Origins, Worlds, and Life Decadal SurveyOrigins, Worlds, and Life: Planetary Science and Astrobiology in the Next Decade identified a Uranus Orbiter and Probe as the highest-priority strategic mission for the decade 2023–2032, as it enables broad cross-disciplinary science in the largely unexplored Uranian system. The mission architecture evaluated by the Decadal Survey was a singular proof of concept demonstrating that a moderately instrumented mission could deliver Decadal-priority science with a reduced cost and risk posture by leveraging existing technologies to the maximum extent possible. With revised assumptions since the Decadal, we have explored a large trade space including launch vehicles, propulsion options, cruise trajectories, available power sources, viable concept of operations, and science data return for later launch dates without a Jupiter gravity assist. The most repeatable trajectory solutions employ either a commercially derived solar electric propulsion (SEP) transfer stage or the availability of a more capable launch vehicle under development, such as the SpaceX Starship. Orbit insertion has been moved farther from Uranus to acknowledge the remaining uncertainty in Uranian ring structure. A streamlined, SEP-adaptable, orbiter design was developed using two Next Gen Radioisotope Thermoelectric Generators, and the probe design was matured, reducing the entry gravitational acceleration, and assuming the largest Decadal-recommended payload to provide margin for future instrument selections. With this updated design, we also constructed a detailed concept of operations for three representative science cases, returning 13–15 Gbit of science data and spacecraft telemetry per ∼34 day orbit.
- The following article is Open accessNuclear Mitigation of Hypothetical Asteroid Threats in Smoothed Particle Hydrodynamics
Isaiah B. Santistevan et al 2026 Planet. Sci. J. 7 196
View article, Nuclear Mitigation of Hypothetical Asteroid Threats in Smoothed Particle HydrodynamicsPDF, Nuclear Mitigation of Hypothetical Asteroid Threats in Smoothed Particle HydrodynamicsDownload ePub, Nuclear Mitigation of Hypothetical Asteroid Threats in Smoothed Particle HydrodynamicsUnlike 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.
- The following article is Open accessNeptune Odyssey: A Flagship Concept for the Exploration of the Neptune–Triton System
Abigail M. Rymer et al 2021 Planet. Sci. J. 2 184
View article, Neptune Odyssey: A Flagship Concept for the Exploration of the Neptune–Triton SystemPDF, Neptune Odyssey: A Flagship Concept for the Exploration of the Neptune–Triton SystemDownload ePub, Neptune Odyssey: A Flagship Concept for the Exploration of the Neptune–Triton SystemThe Neptune Odyssey mission concept is a Flagship-class orbiter and atmospheric probe to the Neptune–Triton system. This bold mission of exploration would orbit an ice-giant planet to study the planet, its rings, small satellites, space environment, and the planet-sized moon Triton. Triton is a captured dwarf planet from the Kuiper Belt, twin of Pluto, and likely ocean world. Odyssey addresses Neptune system-level science, with equal priorities placed on Neptune, its rings, moons, space environment, and Triton. Between Uranus and Neptune, the latter is unique in providing simultaneous access to both an ice giant and a Kuiper Belt dwarf planet. The spacecraft—in a class equivalent to the NASA/ESA/ASI Cassini spacecraft—would launch by 2031 on a Space Launch System or equivalent launch vehicle and utilize a Jupiter gravity assist for a 12 yr cruise to Neptune and a 4 yr prime orbital mission; alternatively a launch after 2031 would have a 16 yr direct-to-Neptune cruise phase. Our solution provides annual launch opportunities and allows for an easy upgrade to the shorter (12 yr) cruise. Odyssey would orbit Neptune retrograde (prograde with respect to Triton), using the moon's gravity to shape the orbital tour and allow coverage of Triton, Neptune, and the space environment. The atmospheric entry probe would descend in ∼37 minutes to the 10 bar pressure level in Neptune's atmosphere just before Odyssey's orbit-insertion engine burn. Odyssey's mission would end by conducting a Cassini-like “Grand Finale,” passing inside the rings and ultimately taking a final great plunge into Neptune's atmosphere.
- The following article is Open accessThe Viability of Glycine Fermentation in Titan’s Subsurface Ocean
Antonin Affholder et al 2025 Planet. Sci. J. 6 86
View article, The Viability of Glycine Fermentation in Titan’s Subsurface OceanPDF, The Viability of Glycine Fermentation in Titan’s Subsurface OceanDownload ePub, The Viability of Glycine Fermentation in Titan’s Subsurface OceanEnergy and nutrient sources for life could be delivered to Titan’s subsurface water ocean from both its surface above and its core below. Organic matter forming de novo in Titan’s atmosphere and depositing on the surface may hydrolyze upon descent into the ocean with impact-generated melt pools sinking through the ice, adding to a primordial inventory released by the core during differentiation and/or across geologic time. This raises the possibility that abiotic organic carbon could fuel heterotrophic carbon assimilation into biomass in Titan’s ocean if it is inhabited. Glycine fermentation is one possible metabolism of interest, because mechanisms exist to transport glycine to Titan’s ocean and anaerobic fermentations do not rely on additional strong oxidants which may not be present on Titan. Using bioenergetic modeling, we show that while conditions favorable to glycine fermentation may exist, they are highly dependent on temperature. Additionally, the ability of that metabolism to fuel a global biosphere is limited by the slow delivery of glycine by impact melt pools (<10 nmolal yr−1 optimistically, with a >1 mmolal primordial component). A total population of 1014–1017 cells (a few kilograms of carbon) can be sustained, amounting to less than 1 cell kg–1 water when diluted through the entire ocean. Constraining notionally detectable biospheres on Titan will therefore require (i) considering localized environments that may concentrate cells, (ii) better characterizing other candidate metabolisms (e.g., degradation of acetylene or polyaromatic hydrocarbons) for quantitative bioenergetic modeling, and (iii) resolving new mechanisms to deliver organics and oxidants for life.
- The following article is Open accessDirect Molecular-scale Insight into Soluble Organic Matter from the Murchison and Aguas Zarcas Meteorites Enabled by 21T FT-ICR MS and Single-molecule HR-AFM Imaging
Joseph W. Frye-Jones et al 2026 Planet. Sci. J. 7 213
View article, Direct Molecular-scale Insight into Soluble Organic Matter from the Murchison and Aguas Zarcas Meteorites Enabled by 21T FT-ICR MS and Single-molecule HR-AFM ImagingPDF, Direct Molecular-scale Insight into Soluble Organic Matter from the Murchison and Aguas Zarcas Meteorites Enabled by 21T FT-ICR MS and Single-molecule HR-AFM ImagingDownload ePub, Direct Molecular-scale Insight into Soluble Organic Matter from the Murchison and Aguas Zarcas Meteorites Enabled by 21T FT-ICR MS and Single-molecule HR-AFM ImagingOrganic material in the Murchison and Aguas Zarcas meteorites preserves molecular records of early solar system chemistry and potential precursors to life. Here, we present an ultra-wide-mass-range molecular analysis of their soluble organic matter (SOM), complemented by high-resolution structural imaging, revealing large and complex soluble hydrocarbon molecules, including Fe-bearing species extending to carbon numbers above C35. We employ polarity-graded sequential solvent extraction combined with 21 Tesla Fourier-transform ion cyclotron resonance mass spectrometry (21T FT-ICR MS). More polar solvents preferentially extract heteroatom-rich, more aliphatic compounds, whereas nonpolar solvents enrich lower-heteroatom, more aromatic species. Over 18,000 molecular formulas were assigned per extract, with mass errors below 80 ppb, sorted into CHO, CHNO, CHNOS, and CHOMg classes. Carbon numbers range from C10–C70, with oxygen contents up to O20. Differences in Fe-associated molecular populations between Murchison and Aguas Zarcas indicate distinct metal-organic interaction regimes. Negative-ion electrospray ionization (ESI) highlights abundant oxygenated species, with the acidic O2 class comprising up to 20% of assigned formulas. In assisted positive-ion ESI, NyOx species dominate, and extensive sodium adduct formation is observed. Organomagnesium compounds are detected primarily in methanol extracts for Murchison and in chloroform extracts for Aguas Zarcas. Aromaticity increases with decreasing solvent polarity. High-resolution noncontact atomic force microscopy (HR-AFM) provides structural images of representative molecules, spanning saturated chains to condensed aromatic cores. The achieved resolution supports detailed structural interpretation and future molecular-level structure determination.
- The following article is Open accessA Whole-planet Model of the Earth without Life for Terrestrial Exoplanet Studies
Samantha Gilbert-Janizek et al 2026 Planet. Sci. J. 7 216
View article, A Whole-planet Model of the Earth without Life for Terrestrial Exoplanet StudiesPDF, A Whole-planet Model of the Earth without Life for Terrestrial Exoplanet StudiesDownload ePub, A Whole-planet Model of the Earth without Life for Terrestrial Exoplanet StudiesAs the only known habitable (and inhabited) planet in the Universe, Earth informs our search for life elsewhere. Future telescopes like the Habitable Worlds Observatory (HWO) will soon look for life on rocky worlds around Sun-like stars, so it is critical that we understand how to distinguish habitable planets from inhabited planets. However, it remains unknown if life is necessary to maintain a habitable planet, or how all of the components of an evolving planet impact habitability over time. As a first step toward answering these questions, we present a coupled interior-atmosphere evolution model of the Earth without life from 50 Myr to 5 Gyr that reproduces 19 key observations of the preindustrial Earth after 4.5 Gyr within estimated measurement uncertainties. We also produce a reflected-light spectrum covering the possible wavelength range of HWO. Our findings suggest that life may not be required to maintain long-term habitable surface conditions. The model presented here is apt for predicting the long-term habitability of Earth-like exoplanets by coupling the interior and surface evolution. By generating realistic reflected-light spectra from evolved atmospheric states, this model represents significant progress towards characterizing the observability of whole-planet evolution, which may ultimately provide a robust abiotic baseline for interpreting biosignature observations with HWO.
- The following article is Open accessA Search for Persistent Rotational Modulation in the Dedicated TESS Observations of Interstellar Comet 3I/ATLAS
Pulat Tadjimuratov 2026 Planet. Sci. J. 7 241
View article, A Search for Persistent Rotational Modulation in the Dedicated TESS Observations of Interstellar Comet 3I/ATLASPDF, A Search for Persistent Rotational Modulation in the Dedicated TESS Observations of Interstellar Comet 3I/ATLASDownload ePub, A Search for Persistent Rotational Modulation in the Dedicated TESS Observations of Interstellar Comet 3I/ATLASWe analyze the dedicated postperihelion observations of interstellar comet 3I/ATLAS obtained by the Transiting Exoplanet Survey Satellite (TESS) during Sector 1751 on 2026 January 15–22. We search for coherent photometric modulation using both the public TESS Science Support Center aperture light curves and an independent, segment-centered aperture extraction from the released background-corrected image cubes. Candidate excursions are vetted at the pixel level, and periodic signals are evaluated using an exploratory 1–48 hr search, irregularly sampled Ornstein–Uhlenbeck simulations, segment-wise moving-block bootstraps, exact tests of eight previously reported periods, cross-product phase comparisons, and sinusoidal injection–recovery experiments. No candidate satisfies the predeclared family-wise, both-null, cross-product criterion. In particular, none of the reported approximately 7–8 or 15–17 hr period hypotheses is recovered as a statistically significant, phase-coherent modulation. The provider photometry reaches targeted 95% recovery thresholds of 19.0–25.0 ppt peak to peak at the literature periods, while the independent extraction reaches 29.5–38.6 ppt. No reviewed isolated excursion is securely attributable to the comet, and no statistically supported aperture-dilution signature is found. The TESS data therefore exclude a persistent coherent modulation comparable to the much larger amplitudes reported during parts of the preperihelion campaign, while remaining compatible with coma dilution, evolving activity morphology, nonstationary modulation, or non-principal-axis rotation.
- The following article is Open accessThrust Faulting and the Late-stage Contraction of the Moon
T. R. Watters et al 2026 Planet. Sci. J. 7 239
View article, Thrust Faulting and the Late-stage Contraction of the MoonPDF, Thrust Faulting and the Late-stage Contraction of the MoonDownload ePub, Thrust Faulting and the Late-stage Contraction of the MoonLunar Reconnaissance Orbiter Camera images have revealed thousands of young thrust fault scarps in the highlands and mare. These relatively small-scale faults are the expression of a period of late-stage lunar global contraction. Here we present the most comprehensive assessment of recent thrust faulting on the Moon and its implications for lunar radius change. Combining the estimate of the fractional areal strain of the highlands from the population of lobate thrust fault scarps with the fractional areal strain of the maria from the population of small mare ridge thrust faults, the total areal contractional strain is estimated to be ∼0.0048% to 0.0053%. This areal strain corresponds to a radial contraction of ∼42 to 46 m. Assuming a uniform rate of radius change over the last 400 Ma, the rate of change is estimated to be a maximum of ∼11 cm Ma−1. The fractional areal strain of the maria contributes little to the total radius change, thus the late-stage radius change is dominated by the highland thrust faults. The isotropic compressional stress induced by this amount of radial contraction is estimated to be ∼4 MPa, consistent with stress drop estimates from recorded shallow moonquakes. Inconsistency between thermal history models that predict much larger amounts of radial contraction and the absence of degraded, ancient highland fault scarps supports a nonmonotonic lunar thermal evolution, possibly due to the insulating effects of a thick, porous megaregolith. Alternatively, the presence of a strong elastic lithosphere may have inhibited thrust faulting until stresses reached a threshold level in the Copernican era.
- The following article is Open accessRethinking Regolith Strength: Why Nonlinearity Matters on Small Bodies
Naomi Murdoch 2026 Planet. Sci. J. 7 240
View article, Rethinking Regolith Strength: Why Nonlinearity Matters on Small BodiesPDF, Rethinking Regolith Strength: Why Nonlinearity Matters on Small BodiesDownload ePub, Rethinking Regolith Strength: Why Nonlinearity Matters on Small BodiesA widely used approach in planetary science to describe the strength and behavior of geological materials is the Mohr–Coulomb equation, yet it actually represents a linear approximation to a nonlinear failure envelope that breaks down at low confining stress. Using an established failure model, we show that while the majority of laboratory and terrestrial conditions lie in the linear regime, low-gravity planetary surfaces are situated in the nonlinear regime, where the bulk mechanical properties (apparent friction angle, apparent cohesion, and shear strength), become strongly stress dependent. We demonstrate that this nonlinearity governs the mechanical response of regolith in the limits of extremely low confining pressure found on low-gravity small-body surfaces, providing an explanation for the observations of very weak and uncohesive asteroid and cometary surfaces. Furthermore, we also show that mechanical properties of small-body regolith vary strongly with depth, with the apparent cohesion varying by orders of magnitude between the upper centimeters and depths of several meters. These results demonstrate that the widespread assumption of constant, stress-independent friction angle and bulk cohesion, inherent to linear strength models, fundamentally misrepresents regolith behaviour under low-gravity conditions, with important implications for small-body geomorphology, surface and rubble pile evolution, regolith simulants, and planetary exploration.
- The following article is Open accessThe Highly Unusual Behavior and Chemical Composition of Interstellar Comet 2I/Borisov
Allison N. Bair et al 2026 Planet. Sci. J. 7 238
View article, The Highly Unusual Behavior and Chemical Composition of Interstellar Comet 2I/BorisovPDF, The Highly Unusual Behavior and Chemical Composition of Interstellar Comet 2I/BorisovDownload ePub, The Highly Unusual Behavior and Chemical Composition of Interstellar Comet 2I/BorisovWe report on imaging, spectroscopy, and narrowband photometry of interstellar comet 2I/Borisov obtained at Lowell Observatory from 2019 September 13 to December 16. We measured chemical composition on 4 nights before perihelion, from October 4 to November 25 (2.466–2.028 au), with CN detections on all nights. Our measurements from October 27 represent the earliest reported detections of C2 and C3, where C2-to-CN and C3-to-CN log production rate ratios were −0.7 and −1.3, respectively. Both ratios increased by nearly 4× to −0.3 and −0.9 by November 25, an extremely large increase with heliocentric distance that is unprecedented in the Lowell Observatory comet database. We additionally observed OH and NH on November 25, with a derived H2O production rate of 4.5 × 1026 mol s−1 and very high log production rate ratios for CN-to-OH (−2.0) and NH-to-OH (−1.7). Monitoring from broadband R images from September 13 to December 16 suggests dust (A(0°)fρ) production peaked around October 19, 50 days before its December 8 perihelion passage. Narrowband images from October 4 and 27 reveal a nearly symmetric CN distribution in Borisov’s coma, suggesting activity over its entire sunward hemisphere and possibly its entire nucleus. Our results, combined with those from others, reveal a chemical composition and behavior with heliocentric distance unlike any other comet we have observed.
- The following article is Open accessGlycine Partitions into Halite during Crystallization in Ceres Simulant Brines
Lucas R. Reynoso et al 2026 Planet. Sci. J. 7 237
View article, Glycine Partitions into Halite during Crystallization in Ceres Simulant BrinesPDF, Glycine Partitions into Halite during Crystallization in Ceres Simulant BrinesDownload ePub, Glycine Partitions into Halite during Crystallization in Ceres Simulant BrinesSalts on Ceres may act as messengers of interior ocean chemistry, trapping organics and preserving parent brine compositions. However, relating organic detections to subsurface brine compositions requires quantifying how much organic material is retained in salt crystals relative to the parent solution, a ratio, to our knowledge, not yet measured for any organic–salt system relevant to ocean worlds. Here, we determine the apparent partition coefficient, α, for glycine (NH2CH2COOH), the simplest and most abundant amino acid in extraterrestrial materials, crystallized in halite (NaCl) from aqueous brine under evaporative conditions. Halite crystals were grown from brines containing 0–133 mM glycine and characterized using optical microscopy, Fourier transform infrared spectroscopy (FTIR), X-ray computed tomography (XCT), and gas chromatography with flame ionization detection (GC-FID). Reflected-light imaging and XCT reveal glycine incorporated as micrometer-scale inclusions rather than substituting into the crystal lattice, with crystal-to-crystal variability consistent with stochastic inclusion trapping. GC-FID yields a linear relationship between glycine concentration in the crystal and the parent brine, with α = 0.177 ± 0.019, meaning NaCl captured ∼18% of available glycine. Applied to Ceres, this implies that glycine concentrations in the subsurface reservoir can be at least 5 times higher than abundances in surface salt deposits and that individual salt grains may be heterogeneous even from a single source brine. This framework provides quantitative constraints for interpreting organic signatures observed in samples returned by a future Ceres mission, as recommended by the 2023–2032 Origins, Worlds, and Life Planetary Science and Astrobiology Decadal Survey.
- The following article is Open accessThe NASA Exoplanet Archive and Exoplanet Follow-up Observing Program: Data, Tools, and Usage
Jessie L. Christiansen et al 2025 Planet. Sci. J. 6 186
View article, The NASA Exoplanet Archive and Exoplanet Follow-up Observing Program: Data, Tools, and UsagePDF, The NASA Exoplanet Archive and Exoplanet Follow-up Observing Program: Data, Tools, and UsageDownload ePub, The NASA Exoplanet Archive and Exoplanet Follow-up Observing Program: Data, Tools, and UsageThe NASA Exoplanet Archive (NEA) and the Exoplanet Follow-up Observing Program service are two widely used resources for the exoplanet community. The NEA provides a complete and accurate accounting of exoplanetary systems published by NASA missions and by the community in the refereed literature. In anticipation of continued exponential growth in the number of exoplanetary systems and the increasing complexity in our characterization of these systems, the NEA has restructured its primary tables and interfaces, as well as extending and standardizing their modes of access. The Exoplanet Follow-up Observing Program service provides the exoplanet community with a venue for coordinating and sharing follow-up and precursor data for exoplanets, their host stars, and stars that might eventually be targets for future planet searches and recently reached 1 million files uploaded by the community. In this paper, we describe the updates to our data holdings, functionality, accessibility, and tools, as well as future priorities for these two services.
- The following article is Open accessThe ESA Hera Mission: Detailed Characterization of the DART Impact Outcome and of the Binary Asteroid (65803) Didymos
Patrick Michel et al 2022 Planet. Sci. J. 3 160
View article, The ESA Hera Mission: Detailed Characterization of the DART Impact Outcome and of the Binary Asteroid (65803) DidymosPDF, The ESA Hera Mission: Detailed Characterization of the DART Impact Outcome and of the Binary Asteroid (65803) DidymosDownload ePub, The ESA Hera Mission: Detailed Characterization of the DART Impact Outcome and of the Binary Asteroid (65803) DidymosHera is a planetary defense mission under development in the Space Safety and Security Program of the European Space Agency for launch in 2024 October. It will rendezvous in late 2026 December with the binary asteroid (65803) Didymos and in particular its moon, Dimorphos, which will be impacted by NASA’s DART spacecraft on 2022 September 26 as the first asteroid deflection test. The main goals of Hera are the detailed characterization of the physical properties of Didymos and Dimorphos and of the crater made by the DART mission, as well as measurement of the momentum transfer efficiency resulting from DART’s impact. The data from the Hera spacecraft and its two CubeSats will also provide significant insights into asteroid science and the evolutionary history of our solar system. Hera will perform the first rendezvous with a binary asteroid and provide new measurements, such as radar sounding of an asteroid interior, which will allow models in planetary science to be tested. Hera will thus provide a crucial element in the global effort to avert future asteroid impacts at the same time as providing world-leading science.
- The following article is Open accessRefining the Transit-timing and Photometric Analysis of TRAPPIST-1: Masses, Radii, Densities, Dynamics, and Ephemerides
Eric Agol et al 2021 Planet. Sci. J. 2 1
View article, Refining the Transit-timing and Photometric Analysis of TRAPPIST-1: Masses, Radii, Densities, Dynamics, and EphemeridesPDF, Refining the Transit-timing and Photometric Analysis of TRAPPIST-1: Masses, Radii, Densities, Dynamics, and EphemeridesDownload ePub, Refining the Transit-timing and Photometric Analysis of TRAPPIST-1: Masses, Radii, Densities, Dynamics, and EphemeridesWe have collected transit times for the TRAPPIST-1 system with the Spitzer Space Telescope over four years. We add to these ground-based, HST, and K2 transit-time measurements, and revisit an N-body dynamical analysis of the seven-planet system using our complete set of times from which we refine the mass ratios of the planets to the star. We next carry out a photodynamical analysis of the Spitzer light curves to derive the density of the host star and the planet densities. We find that all seven planets’ densities may be described with a single rocky mass–radius relation which is depleted in iron relative to Earth, with Fe 21 wt% versus 32 wt% for Earth, and otherwise Earth-like in composition. Alternatively, the planets may have an Earth-like composition but enhanced in light elements, such as a surface water layer or a core-free structure with oxidized iron in the mantle. We measure planet masses to a precision of 3%–5%, equivalent to a radial-velocity (RV) precision of 2.5 cm s−1, or two orders of magnitude more precise than current RV capabilities. We find the eccentricities of the planets are very small, the orbits are extremely coplanar, and the system is stable on 10 Myr timescales. We find evidence of infrequent timing outliers, which we cannot explain with an eighth planet; we instead account for the outliers using a robust likelihood function. We forecast JWST timing observations and speculate on possible implications of the planet densities for the formation, migration, and evolution of the planet system.
- The following article is Open accessThe Near-Earth Object Surveyor Mission
A. K. Mainzer et al 2023 Planet. Sci. J. 4 224
View article, The Near-Earth Object Surveyor MissionPDF, The Near-Earth Object Surveyor MissionDownload ePub, The Near-Earth Object Surveyor MissionThe Near-Earth Object (NEO) Surveyor mission is a NASA Observatory designed to discover and characterize asteroids and comets. The mission’s primary objective is to find the majority of objects large enough to cause severe regional impact damage (>140 m in effective spherical diameter) within its 5 yr baseline survey. Operating at the Sun–Earth L1 Lagrange point, the mission will survey to within 45° of the Sun in an effort to find objects in the most Earth-like orbits. The survey cadence is optimized to provide observational arcs long enough to distinguish near-Earth objects from more distant small bodies that cannot pose an impact hazard reliably. Over the course of its survey, NEO Surveyor will discover ∼200,000–300,000 new NEOs down to sizes as small as ∼10 m and thousands of comets, significantly improving our understanding of the probability of an Earth impact over the next century.
- The following article is Open accessChemical Equilibrium between Cores, Mantles, and Atmospheres of Super-Earths and Sub-Neptunes and Implications for Their Compositions, Interiors, and Evolution
Hilke E. Schlichting and Edward D. Young 2022 Planet. Sci. J. 3 127
View article, Chemical Equilibrium between Cores, Mantles, and Atmospheres of Super-Earths and Sub-Neptunes and Implications for Their Compositions, Interiors, and EvolutionPDF, Chemical Equilibrium between Cores, Mantles, and Atmospheres of Super-Earths and Sub-Neptunes and Implications for Their Compositions, Interiors, and EvolutionDownload ePub, Chemical Equilibrium between Cores, Mantles, and Atmospheres of Super-Earths and Sub-Neptunes and Implications for Their Compositions, Interiors, and EvolutionWe investigate the equilibrium chemistry between molten metal and silicate and a hydrogen-rich envelope using 18 independent reactions among 25 phase components for sub-Neptune-like exoplanets. Both reactive and unreactive metal sequestered in an isolated core are modeled. The overarching effects of equilibration are oxidation of the envelope and reduction of the mantle and core. Hydrogen and oxygen typically comprise significant fractions of metal cores at chemical equilibrium, leading to density deficits that offer a possible alternative explanation for the low densities of the Trappist-1 planets. Reactions with the magma ocean produce significant amounts of SiO and H2O in the envelopes directly above the magma ocean. Molar concentrations in the envelopes of planets with reactive metal are H2 > SiO > CO ∼ Na ∼ Mg > H2O ≫ CO2 ∼ CH4 ≫ O2, while for the unreactive metal case, H2O becomes the second most abundant species, after H2, providing an arbiter for the two scenarios amenable to observation. The water abundances in the atmospheres exceed those in the mantles by at least an order of magnitude in both scenarios. The water concentrations in the silicate mantles are ∼0.01 and ∼0.1 wt% in the reactive and unreactive metal core cases, respectively, limiting the H2O that might be outgassed in a future super-Earth. Less dissolved water in the reactive core case is due to sequestration of H and O in the Fe-rich metal. The total hydrogen budget of most sub-Neptunes can, to first order, be estimated from their atmospheres alone, as the atmospheres typically contain more than 90% of all H.
- The following article is Open accessScience Goals and Objectives for the Dragonfly Titan Rotorcraft Relocatable Lander
Jason W. Barnes et al 2021 Planet. Sci. J. 2 130
View article, Science Goals and Objectives for the Dragonfly Titan Rotorcraft Relocatable LanderPDF, Science Goals and Objectives for the Dragonfly Titan Rotorcraft Relocatable LanderDownload ePub, Science Goals and Objectives for the Dragonfly Titan Rotorcraft Relocatable LanderNASA’s Dragonfly mission will send a rotorcraft lander to the surface of Titan in the mid-2030s. Dragonfly's science themes include investigation of Titan’s prebiotic chemistry, habitability, and potential chemical biosignatures from both water-based “life as we know it” (as might occur in the interior mantle ocean, potential cryovolcanic flows, and/or impact melt deposits) and potential “life, but not as we know it” that might use liquid hydrocarbons as a solvent (within Titan’s lakes, seas, and/or aquifers). Consideration of both of these solvents simultaneously led to our initial landing site in Titan’s equatorial dunes and interdunes to sample organic sediments and water ice, respectively. Ultimately, Dragonfly's traverse target is the 80 km diameter Selk Crater, at 7° N, where we seek previously liquid water that has mixed with surface organics. Our science goals include determining how far prebiotic chemistry has progressed on Titan and what molecules and elements might be available for such chemistry. We will also determine the role of Titan’s tropical deserts in the global methane cycle. We will investigate the processes and processing rates that modify Titan’s surface geology and constrain how and where organics and liquid water can mix on and within Titan. Importantly, we will search for chemical biosignatures indicative of past or extant biological processes. As such, Dragonfly, along with Perseverance, is the first NASA mission to explicitly incorporate the search for signs of life into its mission goals since the Viking landers in 1976.
- The following article is Open accessRevealing the Mysteries of Venus: The DAVINCI Mission
James B. Garvin et al 2022 Planet. Sci. J. 3 117
View article, Revealing the Mysteries of Venus: The DAVINCI MissionPDF, Revealing the Mysteries of Venus: The DAVINCI MissionDownload ePub, Revealing the Mysteries of Venus: The DAVINCI MissionThe Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging (DAVINCI) mission described herein has been selected for flight to Venus as part of the NASA Discovery Program. DAVINCI will be the first mission to Venus to incorporate science-driven flybys and an instrumented descent sphere into a unified architecture. The anticipated scientific outcome will be a new understanding of the atmosphere, surface, and evolutionary path of Venus as a possibly once-habitable planet and analog to hot terrestrial exoplanets. The primary mission design for DAVINCI as selected features a preferred launch in summer/fall 2029, two flybys in 2030, and descent-sphere atmospheric entry by the end of 2031. The in situ atmospheric descent phase subsequently delivers definitive chemical and isotopic composition of the Venus atmosphere during an atmospheric transect above Alpha Regio. These in situ investigations of the atmosphere and near-infrared (NIR) descent imaging of the surface will complement remote flyby observations of the dynamic atmosphere, cloud deck, and surface NIR emissivity. The overall mission yield will be at least 60 Gbits (compressed) new data about the atmosphere and near surface, as well as the first unique characterization of the deep atmosphere environment and chemistry, including trace gases, key stable isotopes, oxygen fugacity, constraints on local rock compositions, and topography of a tessera.
- The following article is Open accessOSIRIS-APEX: An OSIRIS-REx Extended Mission to Asteroid Apophis
Daniella N. DellaGiustina et al 2023 Planet. Sci. J. 4 198
View article, OSIRIS-APEX: An OSIRIS-REx Extended Mission to Asteroid ApophisPDF, OSIRIS-APEX: An OSIRIS-REx Extended Mission to Asteroid ApophisDownload ePub, OSIRIS-APEX: An OSIRIS-REx Extended Mission to Asteroid ApophisThe Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) spacecraft mission characterized and collected a sample from asteroid (101955) Bennu. After the OSIRIS-REx Sample Return Capsule released to Earth’s surface in 2023 September, the spacecraft diverted into a new orbit that encounters asteroid (99942) Apophis in 2029, enabling a second mission with the same unique capabilities: OSIRIS–Apophis Explorer (APEX). On 2029 April 13, the 340 m diameter Apophis will draw within ∼32,000 km of Earth’s surface, less than 1/10 the lunar distance. Apophis will be the largest object to approach Earth this closely in recorded history. This rare planetary encounter will alter Apophis’s orbit, will subject it to tidal forces that change its spin state, and may seismically disturb its surface. APEX will distantly observe Apophis during the Earth encounter and capture its evolution in real time, revealing the consequences of an asteroid undergoing tidal disturbance by a major planet. Beginning in 2029 July, the spacecraft’s instrument suite will begin providing high-resolution data of this “stony” asteroid—advancing knowledge of these objects and their connection to meteorites. Near the mission’s end, APEX will use its thrusters to excavate regolith, a technique demonstrated at Bennu. Observations before, during, and after excavation will provide insight into the subsurface and material properties of stony asteroids. Furthermore, Apophis’s material and structure have critical implications for planetary defense.
- The following article is Open accessThe Double Asteroid Redirection Test (DART): Planetary Defense Investigations and Requirements
Andrew S. Rivkin et al 2021 Planet. Sci. J. 2 173
View article, The Double Asteroid Redirection Test (DART): Planetary Defense Investigations and RequirementsPDF, The Double Asteroid Redirection Test (DART): Planetary Defense Investigations and RequirementsDownload ePub, The Double Asteroid Redirection Test (DART): Planetary Defense Investigations and RequirementsThe Double Asteroid Redirection Test (DART) is a Planetary Defense mission, designed to demonstrate the kinetic impactor technique on (65803) Didymos I Dimorphos, the secondary of the (65803) Didymos system. DART has four level 1 requirements to meet in order to declare mission success: (1) impact Dimorphos between 2022 September 25 and October 2, (2) cause at least a 73 s change in its binary orbit period via the impact, (3) measure the change in binary period to an uncertainty of 7.3 s or less, and (4) measure the momentum transfer efficiency (β) of the impact and characterize the resulting effects of the impact. The data necessary to achieve these requirements will be obtained and analyzed by the DART Investigation Team. We discuss the rationales for the data to be gathered, the analyses to be undertaken, and how mission success will be achieved.
- The following article is Open accessThe Enceladus Orbilander Mission Concept: Balancing Return and Resources in the Search for Life
Shannon M. MacKenzie et al 2021 Planet. Sci. J. 2 77
View article, The Enceladus Orbilander Mission Concept: Balancing Return and Resources in the Search for LifePDF, The Enceladus Orbilander Mission Concept: Balancing Return and Resources in the Search for LifeDownload ePub, The Enceladus Orbilander Mission Concept: Balancing Return and Resources in the Search for LifeEnceladus’s long-lived plume of ice grains and water vapor makes accessing oceanic material readily achievable from orbit (around Saturn or Enceladus) and from the moon’s surface. In preparation for the National Academies of Sciences, Engineering and Medicine 2023–2032 Planetary Science and Astrobiology Decadal Survey, we investigated four architectures capable of collecting and analyzing plume material from orbit and/or on the surface to address the most pressing questions at Enceladus: Is the subsurface ocean inhabited? Why, or why not? Trades specific to these four architectures were studied to allow an evaluation of the science return with respect to investment. The team found that Orbilander, a mission concept that would first orbit and then land on Enceladus, represented the best balance. Orbilander was thus studied at a higher fidelity, including a more detailed science operations plan during both orbital and landed phases, landing site characterization and selection analyses, and landing procedures. The Orbilander mission concept demonstrates that scientifically compelling but resource-conscious Flagship-class missions can be executed in the next decade to search for life at Enceladus.
Journal resources
Journal information
- 2020-present
The Planetary Science Journal
doi: 10.3847/issn.2632-3338
Online ISSN: 2632-3338