The Planetary Science Journal - IOPscience

The Planetary Science Journal - IOPscience
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.
ISSN:
2632-3338
OPEN ACCESS
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.
Submit
an article
opens in new tab
RSS
Sign up for new issue notifications
Impact factor
4.3
The following article is
Open access
Carbon Cycle Imbalances on Arid Terrestrial Planets with Implications for Venus
Haskelle T. White-Gianella and Joshua Krissansen-Totton 2026
Planet. Sci. J.
79
View article
, Carbon Cycle Imbalances on Arid Terrestrial Planets with Implications for Venus
PDF
, Carbon Cycle Imbalances on Arid Terrestrial Planets with Implications for Venus
ePub
, Carbon Cycle Imbalances on Arid Terrestrial Planets with Implications for Venus
Arid terrestrial exoplanets are potentially abundant and are thus interesting targets in the search for life. In particular, M-dwarf planets such as those in the TRAPPIST-1 system may possess limited surface water, whereas early solar system terrestrials may have had small surface water inventories postmagma ocean solidification. On modern Earth, there is enough surface water for a balanced geologic carbon cycle, meaning silicate weathering balances the volcanic outgassing of CO
. However, on arid planets, there may not be enough surface water for this silicate weathering thermostat to maintain habitable conditions. Here, we show that arid planets enter a regime where weathering cannot keep up with volcanic degassing of CO
. Using a coupled model of the geologic carbon cycle, we find that terrestrial Earth-like planets require an initial surface water inventory of at least ∼20%–50% of Earth’s ocean mass to maintain a balanced geologic carbon cycle and temperate surface temperature over 4.5 Gyr of evolution. Arid planets with less than ∼20%–50% of Earth’s oceans cannot maintain high silicate weathering fluxes, potentially causing a runaway increase in atmospheric CO
. In addition, we explore Venus-like instellations and find that limited surface water could have destabilized Venus’s carbon cycle, triggering a transition from temperate to uninhabitable. Even if a planet resides in the habitable zone of its star, if arid, it may transition to an uninhabitable state due to an unbalanced carbon cycle. More broadly, arid terrestrial exoplanets are less likely to remain habitable on long timescales, and may thus be poor candidates for biosignature searches.
The following article is
Open access
Orientale Basin as a Guide for Identifying Lunar Basin Datable Impact Melt and Assessing Impact Melt Differentiation
Kirby Runyon
et al
2024
Planet. Sci. J.
249
View article
, Orientale Basin as a Guide for Identifying Lunar Basin Datable Impact Melt and Assessing Impact Melt Differentiation
PDF
, Orientale Basin as a Guide for Identifying Lunar Basin Datable Impact Melt and Assessing Impact Melt Differentiation
ePub
, Orientale Basin as a Guide for Identifying Lunar Basin Datable Impact Melt and Assessing Impact Melt Differentiation
Two fundamental questions face lunar scientists: (1) What is the absolute age of each lunar impact basin and thus the early impact flux curve? (2) To what degree did basin impact melt seas undergo differentiation? We compiled a 1:200,000-scale geological map of the lunar Orientale basin, focusing on identifying the most widespread and accessible occurrences of impact melt deposits from the basin-forming impact to help guide sample-return missions to Orientale and especially to other undated lunar basins using the identification and interpretation strategies for Orientale. We assess the size of craters excavating through basalt cap rock that may have exhumed datable basin impact melt, and we assess the possibility of impact melt sampling and melt differentiation for the large complex crater Maunder. We also provide guidance for distinguishing impact melt produced by larger complex craters from excavated basin melt and determining whether such craters may have also sampled through the entire melt deposit. Our analysis finds six such sites that are predicted to have the same age—that of the Orientale-forming event—and provides guidance for assessing possible melt differentiation. Future missions could collect samples from these sites for in situ age dating and petrologic assessment and/or for return to Earth and subsequent age dating and analysis. By sampling and dating impact melt of known provenance from the Moon’s dozens of large basins, future work can anchor the chronostratigraphy of the Moon’s formative years. Such information could be scaled to infer Earth’s large impactor flux around the time of life’s first emergence.
The following article is
Open access
The Viability of Glycine Fermentation in Titan’s Subsurface Ocean
Antonin Affholder
et al
2025
Planet. Sci. J.
86
View article
, The Viability of Glycine Fermentation in Titan’s Subsurface Ocean
PDF
, The Viability of Glycine Fermentation in Titan’s Subsurface Ocean
ePub
, The Viability of Glycine Fermentation in Titan’s Subsurface Ocean
Energy 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 10
14
–10
17
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 access
First Use of Laser Ranging to Surface Retroreflectors for Orbit Determination: LRO-LOLA at the Moon
G. Cascioli
et al
2025
Planet. Sci. J.
247
View article
, First Use of Laser Ranging to Surface Retroreflectors for Orbit Determination: LRO-LOLA at the Moon
PDF
, First Use of Laser Ranging to Surface Retroreflectors for Orbit Determination: LRO-LOLA at the Moon
ePub
, First Use of Laser Ranging to Surface Retroreflectors for Orbit Determination: LRO-LOLA at the Moon
We document the first operational demonstration of two-way spacecraft-to-surface laser ranging using Laser Retroreflector Arrays (LRAs) for orbit determination (OD) of the Lunar Reconnaissance Orbiter (LRO). We detail how the Lunar Orbiter Laser Altimeter (LOLA) was operationally adapted to target and successfully range to several LRAs on the lunar surface. Although LOLA was not designed for this purpose, and despite many spacecraft constraints that limited the number of measurements we could collect, we demonstrate that incorporating these ranging observations into OD procedures yields tangible improvements in LRO’s orbital solution. Our analysis yields two key findings: (1) systematic ranging to different types of surface LRAs from orbit is operationally feasible, and (2) such measurements provide valuable geodetic data for spacecraft navigation. This first demonstration is particularly timely as more LRAs are being deployed across the lunar surface through various international and commercial missions, while LiDAR technology continues to advance. Combined with the growing number of missions requiring Position, Navigation, and Timing services in lunar orbit, our findings indicate that spacecraft-to-LRA ranging could become an essential technique for navigation in the near future, complementing traditional Earth-based tracking methods.
The following article is
Open access
A Mars Microbial Survival Model: Calculating Bioburden Reductions for Past Mars Spacecraft to Estimate Forward Contamination on Mars
Grace Bischof
et al
2026
Planet. Sci. J.
37
View article
, A Mars Microbial Survival Model: Calculating Bioburden Reductions for Past Mars Spacecraft to Estimate Forward Contamination on Mars
PDF
, A Mars Microbial Survival Model: Calculating Bioburden Reductions for Past Mars Spacecraft to Estimate Forward Contamination on Mars
ePub
, A Mars Microbial Survival Model: Calculating Bioburden Reductions for Past Mars Spacecraft to Estimate Forward Contamination on Mars
Minimizing the forward contamination of Mars from terrestrial microorganisms is a key objective of planetary protection. To model the survivability of terrestrial spacecraft microorganisms under the biocidal effects of space, as well as on the surface of Mars, a Mars Microbial Survival (MMS) model was developed. The MMS model predicted the bioburden reductions at 14 historical Mars landing sites. During cruise phases, the exteriors of spacecraft aeroshells were sterilized owing to solar UVC irradiation, accumulating several Sterility Assurance Levels (SALs; defined as –12 log reductions from initial starting populations of 10
spores per replicate) even before arriving at Mars. On the surface of Mars, each landed spacecraft would reach one SAL for upward-facing surfaces after only one sol on the surface owing to solar UVC (200–280 nm) irradiation. Over one Mars year, all external surfaces on all landers were likely sterilized by UVC. Contributions from desiccation, low pressure, and biotoxic soils on Mars also produced small additional bioburden reductions. It is unlikely that terrestrial microorganisms will be able to survive on the external surfaces of the landed spacecraft considered in this work. Internally, heated components of the spacecraft may reach one SAL in ∼100 sols, but nonheated internal components might take as long as 25 Mars years to be sterilized.
The following article is
Open access
Surface Heterogeneity, Physical, and Shape Model of Near-Earth Asteroid (52768) 1998 OR2
Maxime Devogèle
et al
2024
Planet. Sci. J.
44
View article
, Surface Heterogeneity, Physical, and Shape Model of Near-Earth Asteroid (52768) 1998 OR2
PDF
, Surface Heterogeneity, Physical, and Shape Model of Near-Earth Asteroid (52768) 1998 OR2
ePub
, Surface Heterogeneity, Physical, and Shape Model of Near-Earth Asteroid (52768) 1998 OR2
On 2020 April 29, the near-Earth object (52768) 1998 OR2 experienced a close approach to Earth at a distance of 16.4 lunar distances (LD). 1998 OR2 is a potentially hazardous asteroid of absolute magnitude
= 16.04 that can currently come as close to Earth as 3.4 LD. We report here observations of this object in polarimetry, photometry, and radar. Our observations show that the physical characteristics of 1998 OR2 are similar to those of both M- and S-type asteroids. Arecibo’s radar observations provide a high radar albedo of
0.29 ± 0.08, suggesting that metals are present in 1998 OR2 near-surface. We find a circular polarization ratio of
= 0.291 ± 0.012, and the delay-Doppler images show that the surface of 1998 OR2 is a top-shape asteroid with large-scale structures such as large craters and concavities. The polarimetric observations display a consistent variation of the polarimetric response as a function of the rotational phase, suggesting that the surface of 1998 OR2 is heterogeneous. Color observations suggest an X-complex taxonomy in the Bus–DeMeo classification. Combining optical polarization, radar, and two epochs from the NEOWISE satellite observations, we derived an equivalent diameter of
= 1.80 ± 0.1 km and a visual albedo
= 0.21 ± 0.02. Photometric and radar data provide a sidereal rotation period of
= 4.10872 ± 0.00001 hr, a pole orientation of (332
3 ± 5°, 20
7 ± 5°), and a shape model with dimensions of
km.
The following article is
Open access
Probabilistic Modeling of Lunar Topography for Exosphere Simulations and Implications for Helium, Neon, and Argon
Alexander Peschel
et al
2026
Planet. Sci. J.
69
View article
, Probabilistic Modeling of Lunar Topography for Exosphere Simulations and Implications for Helium, Neon, and Argon
PDF
, Probabilistic Modeling of Lunar Topography for Exosphere Simulations and Implications for Helium, Neon, and Argon
ePub
, Probabilistic Modeling of Lunar Topography for Exosphere Simulations and Implications for Helium, Neon, and Argon
We introduce a numerically efficient approach to include lunar surface topography in Monte Carlo exosphere simulations by sampling slope and azimuth angles from latitude-dependent Lunar Orbiter Laser Altimeter distributions and rotating particle release directions accordingly. A probabilistic temperature model, driven by the local slope statistics, provides a temperature distribution at each location and captures shadowing effects, particularly across the terminators. Applied to helium, neon, and argon, the method yields shallower trajectories of these elements when released to the exosphere and modified loss processes, increasing the globally averaged number densities by up to 8%, with stronger effects for neon and argon than for helium due to their higher masses. These results indicate that topography influences both the near-surface densities and higher-altitude behavior, with direct implications for comparing surface measurements to orbital observations. The study establishes a practical first step toward topography-aware exosphere modeling and motivates the further development of a fitted temperature description, with particular attention to the terminator regions. Notably, even this preliminary temperature model already shows improved agreement with Diviner measurements compared to previous analytical approaches.
The following article is
Open access
The Geology of a Small Main-belt S-class Binary Asteroid System: Dinkinesh and Its Contact Binary Satellite Selam as Observed by the Lucy Mission
E. B. Bierhaus
et al
2025
Planet. Sci. J.
299
View article
, The Geology of a Small Main-belt S-class Binary Asteroid System: Dinkinesh and Its Contact Binary Satellite Selam as Observed by the Lucy Mission
PDF
, The Geology of a Small Main-belt S-class Binary Asteroid System: Dinkinesh and Its Contact Binary Satellite Selam as Observed by the Lucy Mission
ePub
, The Geology of a Small Main-belt S-class Binary Asteroid System: Dinkinesh and Its Contact Binary Satellite Selam as Observed by the Lucy Mission
The Lucy spacecraft flew past the ∼738 m diameter, S-class main-belt asteroid (152830) Dinkinesh on 2023 November 1, revealing a satellite named Selam. We used images acquired during the flyby to evaluate surface features on both Dinkinesh and Selam. We find a shallow crater size–frequency distribution (SFD) for Dinkinesh, consistent with crater SFDs observed on other subkilometer asteroids. We derive crater depth-to-diameter ratios near 0.1, also consistent with typical values seen on other asteroids. We calculate a cumulative boulder SFD for Dinkinesh with power-law index 3.93 ± 0.15 slightly steeper though in the range of other S-class asteroids. We find growing evidence that boulder SFDs are, on average, steeper for S-class than C-complex asteroids. Two major surface features on Dinkinesh, Sumak Fossa (a large trough) and Fab Dorsum (an equatorial ridge), are likely an outcome of YORP spinning up Dinkinesh fast enough to produce failure. A self-consistent structure for Dinkinesh that complies with the global shape, feature morphologies, and the estimated 10–20 Myr YORP spin-up timescale is a rubble-pile object with a nearly strengthless surface and an interior strength that is less than tens of Pa. Selam could have formed via YORP-driven mass shedding from Dinkinesh, though other formation mechanisms are possible. Combining a low-strength surface with the crater population and an impact model, we estimate a ∼1 Myr surface age for Dinkinesh. The presence of mass wasting and young troughs indicates that stress accumulation and release continue on Dinkinesh to the present day.
The following article is
Open access
The NASA Exoplanet Archive and Exoplanet Follow-up Observing Program: Data, Tools, and Usage
Jessie L. Christiansen
et al
2025
Planet. Sci. J.
186
View article
, The NASA Exoplanet Archive and Exoplanet Follow-up Observing Program: Data, Tools, and Usage
PDF
, The NASA Exoplanet Archive and Exoplanet Follow-up Observing Program: Data, Tools, and Usage
ePub
, The NASA Exoplanet Archive and Exoplanet Follow-up Observing Program: Data, Tools, and Usage
The 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 access
Variations in Lunar Crater Populations due to Target Properties and Secondary Craters
Jean-Pierre Williams
et al
2026
Planet. Sci. J.
64
View article
, Variations in Lunar Crater Populations due to Target Properties and Secondary Craters
PDF
, Variations in Lunar Crater Populations due to Target Properties and Secondary Craters
ePub
, Variations in Lunar Crater Populations due to Target Properties and Secondary Craters
Absolute model ages (AMAs) are derived from crater size–frequency distributions (CSFDs), but these estimates can be subject to biases introduced by local terrain properties and secondary craters. We investigated crater populations superposed on the ejecta deposits of five young Copernican-age craters, spanning a range of ages (∼(1–44) × 10
yr) and sizes (2.3–24 km), and compared spatial crater densities with Lunar Reconnaissance Orbiter Diviner–derived rock abundance and regolith temperature maps. We found that crater spatial densities decrease with increasing rock abundance and regolith temperature at all locations studied, suggesting that impacts into boulders and melt deposits inhibit crater formation via an armoring or crater-scaling effect. This effect persists at rock fractions as low as ∼5%. A direct consequence is that CSFDs in high rock abundance regions have shallower slopes and yield systematically younger AMAs. Conversely, areas with lower rock abundance exhibit CSFD slopes that are steeper than predicted by production functions, consistent with a pervasive presence of self-secondary craters. The opposing influences of target properties (shallower slope) and self-secondaries (steeper slope) result in a critical divergence in CSFDs at smaller diameters between areas with lower (<5%) and higher (>5%) rock abundance. The application of a regolith gardening model indicates that gardening depths of up to ∼20 cm are insufficient to discernibly eliminate heterogeneous target properties. These effects confound straightforward interpretations of CSFDs for small, meter-to-decameter crater diameters. We recommend inspection of CSFD slopes against production functions and prioritization of larger crater diameters when deriving AMAs.
The following article is
Open access
NEO Colors from the Mission Accessible Near-Earth Object Survey (MANOS)
Nicholas Moskovitz
et al
2026
Planet. Sci. J.
89
View article
, NEO Colors from the Mission Accessible Near-Earth Object Survey (MANOS)
PDF
, NEO Colors from the Mission Accessible Near-Earth Object Survey (MANOS)
ePub
, NEO Colors from the Mission Accessible Near-Earth Object Survey (MANOS)
We present spectro-photometric
griz
colors for 189 near-Earth objects (NEOs) collected by the Mission Accessible Near-Earth Object Survey (MANOS). Data acquisition involved nonsimultaneous multiband exposures; thus, particular attention was given to the influence of rotational lightcurves on the derived colors. We show that colors measured without accounting for lightcurve variations can significantly influence results for individual objects and potentially introduce systematic offsets for ensemble studies. Color-based taxonomic classifications were used to investigate the distribution of spectral types. Our results were combined with other visible wavelength surveys to highlight a previously reported change in the observed taxonomic distribution of NEOs as a function of size, namely a decrease in S complex and an increase in X complex objects with increasing absolute magnitude. Plausibility arguments are given to suggest that Main Belt source region, thermal modification, discovery bias, tidal resurfacing, regolith grain size, and impact shock darkening are unlikely explanations for this size-dependent trend. Consistent with recent NEO population models and work on the connection between meteorites and young asteroid families in the Main Belt, this trend is best explained by a compositional gradient in the NEO population. In particular, the observed abundance of S complex or ordinary chondrite-like NEOs decreases by a factor of 2, from ∼65% of the population at kilometer scales down to a third at sizes ≲50 m. This result has implications for understanding the initial pre-impact population of meteorite parent bodies prior to atmospheric filtering. Furthermore, this will have implications for probabilistic impact risk assessment models.
The following article is
Open access
Spectral Similarity in the Thermal Infrared between Sulfide-rich Carbonaceous Chondrite Meteorites, Jupiter Trojans, and Other D- and P-type Asteroids
Helena C. Bates
et al
2026
Planet. Sci. J.
90
View article
, Spectral Similarity in the Thermal Infrared between Sulfide-rich Carbonaceous Chondrite Meteorites, Jupiter Trojans, and Other D- and P-type Asteroids
PDF
, Spectral Similarity in the Thermal Infrared between Sulfide-rich Carbonaceous Chondrite Meteorites, Jupiter Trojans, and Other D- and P-type Asteroids
ePub
, Spectral Similarity in the Thermal Infrared between Sulfide-rich Carbonaceous Chondrite Meteorites, Jupiter Trojans, and Other D- and P-type Asteroids
Carbonaceous chondrite meteorites, which include the sulfide-rich “Yamato-type” chondrites (CYs), have undergone a complex history of aqueous and thermal alteration and offer crucial insights into early outer solar system conditions. In this study, we evaluate thermal infrared (TIR) reflectance spectra of three CY chondrites. We observe a broad spectral plateau near 10
m, a spectral signature that has been observed in remote observations of some primitive, low-albedo asteroids, including Jupiter Trojans. We compare our data to CY emissivity spectra, spectra of Fe-sulfide and olivine mixtures, and remote Jupiter Trojan observations and establish the plateau and low albedo are a result of a high content of fine-particulate Fe-sulfide of these meteorites. We therefore suggest that D- and P-type asteroids, like Jupiter’s Trojan asteroids, could have a high abundance of Fe sulfide on their surfaces as a potential result of aqueous alteration followed by dehydration, shedding light on the processes shaping the outer solar system.
The following article is
Open access
A Portrait throughout Perihelion of the NH
-rich Interstellar Comet 2I/Borisov
Sophie E. Deam
et al
2026
Planet. Sci. J.
88
View article
, A Portrait throughout Perihelion of the NH2-rich Interstellar Comet 2I/Borisov
PDF
, A Portrait throughout Perihelion of the NH2-rich Interstellar Comet 2I/Borisov
ePub
, A Portrait throughout Perihelion of the NH2-rich Interstellar Comet 2I/Borisov
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
, NH
, 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
, NH
, and CN production rates all increased, with NH
being the most significant; the dust emission also slightly reddened. 2I/Borisov is a carbon-depleted, relatively NH
-rich comet when compared to those comets yet measured in the solar system.
The following article is
Open access
Physical Analysis of Bennu Samples Reveals Regolith Production by Collisional Disruption on Near-Earth Asteroids
R.-L. Ballouz
et al
2026
Planet. Sci. J.
87
View article
, Physical Analysis of Bennu Samples Reveals Regolith Production by Collisional Disruption on Near-Earth Asteroids
PDF
, Physical Analysis of Bennu Samples Reveals Regolith Production by Collisional Disruption on Near-Earth Asteroids
ePub
, Physical Analysis of Bennu Samples Reveals Regolith Production by Collisional Disruption on Near-Earth Asteroids
Due to the extremely low gravity of small near-Earth asteroids (NEAs), it has been assumed that impact-generated rock fragments escape into space and thus do not contribute to the accumulation of regolith. However, centimeter-sized stones returned from the small NEA Bennu by NASA’s OSIRIS-REx mission exhibit impact craters up to a few millimeters wide, implying that impact fragments and impact-processed rocks are retained despite the microgravity environment. To understand how, we combined detailed physical analysis of Bennu samples, laboratory experiments of impacts into simulant rocks, and 3D numerical simulations of disruptive impacts into boulders. We find that the majority (∼85% by mass) of impact fragments eject toward and penetrate the asteroid’s weak, porous surface, leading to their retention. In addition, crater depth-to-diameter ratios (
d/D
) suggest that the Bennu samples (median crater
d/D
= 0.36 ± 0.1) are structurally representative of the asteroid’s large boulders (median crater
d/D
= 0.33 ± 0.08, measured previously). Our analyses indicate that most of Bennu’s surface rocks (those with diameters ≲20 m) could be products of in situ collisional disruption. This impact-driven mechanism of regolith production likely occurs on other small NEAs with highly porous surfaces.
The following article is
Open access
Characterization of Europa’s Interior through Synthesis of Europa Clipper Data
Flavio Petricca
et al
2026
Planet. Sci. J.
86
View article
, Characterization of Europa’s Interior through Synthesis of Europa Clipper Data
PDF
, Characterization of Europa’s Interior through Synthesis of Europa Clipper Data
ePub
, Characterization of Europa’s Interior through Synthesis of Europa Clipper Data
Europa Clipper will arrive in the Jupiter system in 2030 to explore Jupiter’s moon Europa, where it will investigate the habitability of Europa’s subsurface ocean. Characterizing Europa’s ice shell and ocean through geophysical measurements will enable this overarching goal. We present a methodology to combine static gravity, magnetic induction, gravitational tides, and rotational state and orientation measurements with compositional data to characterize Europa’s hydrosphere, simultaneously constraining the ice shell thickness and the ocean thickness and salinity. We applied this methodology to a large number of plausible interior configurations to simulate a broad range of possible scenarios that Europa Clipper might encounter. The result is a prediction of the interior measurement capabilities of the mission, provided in terms of the quality of the interior recovery from the data. We find that the combination of static gravity, magnetic induction, and tidal response enables a full characterization of Europa’s hydrosphere consistent with Europa Clipper’s requirements. Measuring Europa’s tidal response will be crucial to breaking the degeneracies of the interior models to derive the ocean’s salinity. We predict that Europa Clipper will be able to meet its interior science objectives in the vast majority of cases, with the only outliers being end-member cases where the ice shell or ocean is only a few kilometers thick.
The following article is
Open access
The 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.
160
View article
, The ESA Hera Mission: Detailed Characterization of the DART Impact Outcome and of the Binary Asteroid (65803) Didymos
PDF
, The ESA Hera Mission: Detailed Characterization of the DART Impact Outcome and of the Binary Asteroid (65803) Didymos
ePub
, The ESA Hera Mission: Detailed Characterization of the DART Impact Outcome and of the Binary Asteroid (65803) Didymos
Hera 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 access
The NASA Exoplanet Archive and Exoplanet Follow-up Observing Program: Data, Tools, and Usage
Jessie L. Christiansen
et al
2025
Planet. Sci. J.
186
View article
, The NASA Exoplanet Archive and Exoplanet Follow-up Observing Program: Data, Tools, and Usage
PDF
, The NASA Exoplanet Archive and Exoplanet Follow-up Observing Program: Data, Tools, and Usage
ePub
, The NASA Exoplanet Archive and Exoplanet Follow-up Observing Program: Data, Tools, and Usage
The 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 access
Refining the Transit-timing and Photometric Analysis of TRAPPIST-1: Masses, Radii, Densities, Dynamics, and Ephemerides
Eric Agol
et al
2021
Planet. Sci. J.
View article
, Refining the Transit-timing and Photometric Analysis of TRAPPIST-1: Masses, Radii, Densities, Dynamics, and Ephemerides
PDF
, Refining the Transit-timing and Photometric Analysis of TRAPPIST-1: Masses, Radii, Densities, Dynamics, and Ephemerides
ePub
, Refining the Transit-timing and Photometric Analysis of TRAPPIST-1: Masses, Radii, Densities, Dynamics, and Ephemerides
We 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
-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 access
Chemical 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.
127
View article
, Chemical Equilibrium between Cores, Mantles, and Atmospheres of Super-Earths and Sub-Neptunes and Implications for Their Compositions, Interiors, and Evolution
PDF
, Chemical Equilibrium between Cores, Mantles, and Atmospheres of Super-Earths and Sub-Neptunes and Implications for Their Compositions, Interiors, and Evolution
ePub
, Chemical Equilibrium between Cores, Mantles, and Atmospheres of Super-Earths and Sub-Neptunes and Implications for Their Compositions, Interiors, and Evolution
We 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 H
O in the envelopes directly above the magma ocean. Molar concentrations in the envelopes of planets with reactive metal are H
> SiO > CO ∼ Na ∼ Mg > H
O ≫ CO
∼ CH
≫ O
, while for the unreactive metal case, H
O becomes the second most abundant species, after H
, 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 H
O 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 access
The Near-Earth Object Surveyor Mission
A. K. Mainzer
et al
2023
Planet. Sci. J.
224
View article
, The Near-Earth Object Surveyor Mission
PDF
, The Near-Earth Object Surveyor Mission
ePub
, The Near-Earth Object Surveyor Mission
The 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 access
The Double Asteroid Redirection Test (DART): Planetary Defense Investigations and Requirements
Andrew S. Rivkin
et al
2021
Planet. Sci. J.
173
View article
, The Double Asteroid Redirection Test (DART): Planetary Defense Investigations and Requirements
PDF
, The Double Asteroid Redirection Test (DART): Planetary Defense Investigations and Requirements
ePub
, The Double Asteroid Redirection Test (DART): Planetary Defense Investigations and Requirements
The 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 (
) 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 access
Lucy Mission to the Trojan Asteroids: Science Goals
Harold F. Levison
et al
2021
Planet. Sci. J.
171
View article
, Lucy Mission to the Trojan Asteroids: Science Goals
PDF
, Lucy Mission to the Trojan Asteroids: Science Goals
ePub
, Lucy Mission to the Trojan Asteroids: Science Goals
The Lucy Mission is a NASA Discovery-class mission to send a highly capable and robust spacecraft to investigate seven primitive bodies near both the L
and L
Lagrange points with Jupiter: the Jupiter Trojan asteroids. These planetesimals from the outer planetary system have been preserved since early in solar system history. The Lucy mission will fly by and extensively study a diverse selection of Trojan asteroids, including all the recognized taxonomic classes, a collisional family member, and a near equal-mass binary. It will visit objects with diameters ranging from roughly 1 km to 100 km. The payload suite consists of a color camera and infrared imaging spectrometer, a high-resolution panchromatic imager, and a thermal infrared spectrometer. Additionally, two spacecraft subsystems will also contribute to the science investigations: the terminal tracking cameras will supplement imaging during closest approach and the telecommunication subsystem will be used to measure the mass of the Trojans. The science goals are derived from the 2013 Planetary Decadal Survey and include determining the surface composition, assessing the geology, determining the bulk properties, and searching for satellites and rings.
The following article is
Open access
Revealing the Mysteries of Venus: The DAVINCI Mission
James B. Garvin
et al
2022
Planet. Sci. J.
117
View article
, Revealing the Mysteries of Venus: The DAVINCI Mission
PDF
, Revealing the Mysteries of Venus: The DAVINCI Mission
ePub
, Revealing the Mysteries of Venus: The DAVINCI Mission
The 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 access
Achievement of the Planetary Defense Investigations of the Double Asteroid Redirection Test (DART) Mission
Nancy L. Chabot
et al
2024
Planet. Sci. J.
49
View article
, Achievement of the Planetary Defense Investigations of the Double Asteroid Redirection Test (DART) Mission
PDF
, Achievement of the Planetary Defense Investigations of the Double Asteroid Redirection Test (DART) Mission
ePub
, Achievement of the Planetary Defense Investigations of the Double Asteroid Redirection Test (DART) Mission
NASA's Double Asteroid Redirection Test (DART) mission was the first to demonstrate asteroid deflection, and the mission's Level 1 requirements guided its planetary defense investigations. Here, we summarize DART's achievement of those requirements. On 2022 September 26, the DART spacecraft impacted Dimorphos, the secondary member of the Didymos near-Earth asteroid binary system, demonstrating an autonomously navigated kinetic impact into an asteroid with limited prior knowledge for planetary defense. Months of subsequent Earth-based observations showed that the binary orbital period was changed by –33.24 minutes, with two independent analysis methods each reporting a 1
uncertainty of 1.4 s. Dynamical models determined that the momentum enhancement factor,
, resulting from DART's kinetic impact test is between 2.4 and 4.9, depending on the mass of Dimorphos, which remains the largest source of uncertainty. Over five dozen telescopes across the globe and in space, along with the Light Italian CubeSat for Imaging of Asteroids, have contributed to DART's investigations. These combined investigations have addressed topics related to the ejecta, dynamics, impact event, and properties of both asteroids in the binary system. A year following DART's successful impact into Dimorphos, the mission has achieved its planetary defense requirements, although work to further understand DART's kinetic impact test and the Didymos system will continue. In particular, ESA's Hera mission is planned to perform extensive measurements in 2027 during its rendezvous with the Didymos–Dimorphos system, building on DART to advance our knowledge and continue the ongoing international collaboration for planetary defense.
The following article is
Open access
Science Goals and Objectives for the Dragonfly Titan Rotorcraft Relocatable Lander
Jason W. Barnes
et al
2021
Planet. Sci. J.
130
View article
, Science Goals and Objectives for the Dragonfly Titan Rotorcraft Relocatable Lander
PDF
, Science Goals and Objectives for the Dragonfly Titan Rotorcraft Relocatable Lander
ePub
, Science Goals and Objectives for the Dragonfly Titan Rotorcraft Relocatable Lander
NASA’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.
Journal links
Submit an article
About the journal
Author instructions
Editorial board
Copyright and permissions
Ethics policy
Publication charges
Focus issues
AAS Publications
The Astrophysical Journal
The Astronomical Journal
The Astrophysical Journal Letters
The Astrophysical Journal Supplement Series
The Planetary Science Journal
Research Notes of the AAS
Journal information
2020-present
The Planetary Science Journal
doi: 10.3847/issn.2632-3338
Online ISSN: 2632-3338