Dynamically studying trans-Neptunian object (TNO) binaries allows us to measure masses and orbits. Most of the known objects appear to have only two components, except (47171) Lempo, which is the single known hierarchical triple system with three similar-mass components. Though hundreds of TNOs have been imaged with high-resolution telescopes, no other hierarchical triples (or trinaries) have been found among solar system small bodies, even though they are predicted in planetesimal formation models such as gravitational collapse after the streaming instability. By going beyond the point-mass assumption and modeling TNO orbits as non-Keplerian, we open a new window into the shapes and spins of the components, including the possible presence of unresolved "inner" binaries. Here we present evidence for a new hierarchical triple, (148780) Altjira (2001 UQ₁₈), based on non-Keplerian dynamical modeling of the two observed components. We incorporate two recent Hubble Space Telescope observations, leading to a 17 yr observational baseline. We present a new open-source Bayesian point-spread function fitting code called nPSF that provides precise relative astrometry and uncertainties for single images. Our non-Keplerian analysis measures a statistically significant (∼2.5σ) nonspherical shape for Altjira. The measured J₂ is best explained as an unresolved inner binary, and an example hierarchical triple model gives the best fit to the observed astrometry. Using an updated non-Keplerian ephemeris (which is significantly different from the Keplerian predictions), we show that the predicted mutual event season for Altjira has already begun, with several excellent opportunities for observations through ∼2030.

The NASA Lucy mission is scheduled to fly by the main-belt asteroid (52246) Donaldjohanson on 2025 April 20. Donaldjohanson (DJ hereafter) is a member of the primitive (C-type class) Erigone collisional asteroid family located in the inner main belt in proximity of the source regions of asteroids (101955) Bennu and (162173) Ryugu, visited respectively by the OSIRIS-REx and Hayabusa2 missions. In this paper we provide an updated model for the Erigone family age and discuss DJ evolution resulting from nongravitational forces (namely Yarkovsky and Yarkovsky–O'Keefe–Radzievski–Paddack (YORP)), as well as its collisional evolution. We conclude that the best-fit family age is 155 Myr and that, on such timescales, both Yarkovsky and YORP effects may have affected the orbit and spin properties of DJ. Furthermore, we discuss how the NASA Lucy mission could provide independent insights on such processes, namely by constraining DJ shape, surface geology, and cratering history.

Interstellar material has been discovered in our solar system, yet its origins and details of its transport are unknown. Here, we present α Centauri as a case study of the delivery of interstellar material to our solar system. α Centauri is a mature triple star system that likely harbors planets, and is moving toward us with the point of the closest approach approximately 28,000 yr in the future. Assuming a current ejection model for the system, we find that such material can reach our solar system and may currently be present here. The material that does reach us is mostly a product of low (<2 km s⁻¹) ejection velocities, and the rate at which it enters our solar system is expected to peak around the time of α Centauri's closest approach. If α Centauri ejects material at a rate comparable to our own solar system, we estimate the current number of α Centauri particles larger than 100 m in diameter within our Oort Cloud to be 10⁶, and during α Centauri's closest approach, this will increase by an order of magnitude. However, the observable fraction of such objects remains low as there is only a probability of 10⁻⁶ that one of them is within 10 au of the Sun. A small number (∼10) of meteors >100 μm from α Centauri may currently be entering Earth's atmosphere every year: this number is very sensitive to the assumed ejected mass distribution, but the flux is expected to increase as α Centauri approaches.

A strategy for planetary exploration using a rover capable of science autonomy is presented. We encoded into a rover a set of driving hypotheses pertaining to the geologic origin of a field site and equipped the rover with the instrumentation needed to measure the observables related to the hypotheses, as well as the software tools to analyze them to a relatively high level of confidence. We investigated the effects of different exploration strategies that make use of rover science autonomy and compared the operational efficiency and science yield of three geological exploration scenarios: (1) standard human-directed exploration, (2) rover-directed exploration, and (3) astronaut/rover collaborative exploration. We show that exploration with a rover capable of science autonomy is operationally more efficient than the human-directed strategy, resulting in higher rates of data collection and hence a greater science yield per command cycle. Additionally, we explored and developed astronaut/rover collaborative exploration strategies and present a basic framework for effective planetary exploration that leverages the expertise of a science team, the efficiency of a science-autonomous rover, and the contextual abilities of astronauts.

The Schrödinger basin on the south polar lunar far side has been highlighted as a promising target for future exploration. This report provides a high-resolution geologic map in the southwest peak-ring (SWPR) area of the Schrödinger basin, emphasizing structural features and detailed mapping of exposed outcrops within the peak ring. Outcrops are correlated with mineralogical data from the Moon Mineralogical Mapper instrument. Geologic mapping reveals a complex structural history within the basin through a system of radially oriented faults. Further, the geologic map shows both faulted and magmatic contacts between peak-ring mineralogies, providing both structural and magmatic context for understanding lunar crustal evolution and polar region processes. To investigate these relationships and address key scientific concepts and goals from the National Research Council (NRC) report, we propose three traverse paths for a robotic sample return mission in the SWPR area. These traverses focus on addressing the highest priority science concepts and goals by investigating known outcrops with diverse mineralogical associations and visible contacts among them. Coinciding with the preparation for the 2024 Artemis III mission, NASA is increasing the priority of robotic exploration at the lunar south pole before the next crewed mission to the Moon. Through mapping the Schrödinger SWPR, we identified the extent of different lunar crustal mineralogies, inferred their geologic relationships and distribution, and pinpointed traversable routes to sample spectrally diverse outcrops and outcrop-derived boulders. The SWPR region is therefore a promising potential target for future exploration, capable of addressing multiple high-priority lunar science goals.

In contrast with regional primarily methane composition, Kiladze and its surroundings exhibit a water-ice spectral signature that carries an ammoniated compound, similar to two other cryovolcanic sites on Pluto. The faulted structure of Kiladze, including shaping by numerous collapse pits and the distortion of the shape of the depression, are compatible with the surroundings in Hayabusa Terra, east of Sputnik Planitia. They are further compatible with an interpretation as a caldera formed during an era of an active cryovolcanic period that appears to be significantly more recent than the overall age of the planet's surface, possibly in the last several million years. In view of the size of the caldera and the large scale of the surrounding distribution of water ice, we suggest that Kiladze may have been a cryovolcano, in which one or more explosive events may have erupted ∼1000 km³ of icy cryomagma onto the surface.

Saturn's moon Titan is an enigmatic icy world whose surface is constantly modified by its active, Earthlike precipitation system. Here, we propose the Titan's Hydrocarbons: Uncovering New Dimensions of Evolutionary pRocesses (THUNDER) mission concept to investigate how Titan's surface reflects the nature of its interior and its active hydrocarbon cycle. This mission will change our understanding of Titan's surface through three science objectives: characterizing the heat and material transport properties of Titan's icy outer layer, tracing surface liquid storage through and across the crust, and assessing the total hydrocarbon budget through time. This New Frontiers-class mission, designed as part of the Jet Propulsion Laboratory Planetary Science Summer School, responds directly to the call for a Titan orbiter in the NASA Planetary Science and Astrobiology Decadal Survey 2023–2032. THUNDER's focused geology and geophysics mission could achieve full surface mapping to complement both the Cassini–Huygens and Dragonfly missions using gravity science, radar with three operational modes, and a visible-to-infrared spectrometer. These instruments together could give us the first look at Titan as a fully connected and geologically active world, revolutionizing our understanding of icy bodies, fluvial and atmospheric processes, and habitability across geologic time. Here, we summarize the goals of the science mission and engineering approaches, as well as challenges and future directions to study before THUNDER can become a viable mission concept.

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.

Mars has an extensive yet poorly understood cryosphere. Nevertheless, both direct and indirect evidence indicates extensive buried ice across the midlatitudes, including locations where it is presently unstable. While much progress has been made in exploring the processes responsible for ice deposition and preservation during recent climatic fluctuations, a global assessment of the multiple ice reservoirs remains elusive. Motivated by science and the need to find suitable human landing sites, the Mars Subsurface Water Ice Mapping (SWIM) project has developed techniques to map out buried ice. Through integration of all appropriate orbital data sets, the SWIM project produces ∼3 km pixel⁻¹ ice consistency maps over depth ranges of 0–1 m, 1–5 m, and >5 m. In concert with other studies, prior SWIM phases have recognized the uncertainty in our understanding of the geographic and vertical distribution of ice, especially between depths of 1 m and 10 m, creating a push for new ice-prospecting orbital missions, such as the International Mars Ice Mapper mission concept. Here we document the latest SWIM phase, which provides notional targeting maps of the lowest-latitude ice for future missions via a significant improvement in the geomorphic component of our work. The new mapping incorporates both an enhancement in our mapping of geomorphic features and surveys of thermal contraction crack polygons. Our results demonstrate the highly variable nature of the spatial distribution of the shallowest ground ice, with the most equatorward excursions occurring below 30° latitude N/S, locations thought to be out of equilibrium with the current climate.

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.

Determining the physical dimensions of hypervelocity impact structures is challenging due to erosion of their primary relief features on Earth. Critical measurements, such as outer rim diameter, are important for estimating the kinetic energy released and subsequent environmental effects. We developed a Radial Profile Analysis System algorithm, which uses a digital elevation model (DEM) to identify topographic rings surrounding a complex impact structure through an iterative process that assigns the most consistently identified positive relief ring as the apparent outer rim. We investigated five terrestrial impact structures across a range of apparent diameters whose physical dimensions are well established from geological or geophysical studies. Multiple DEM data sets from 2 to 30 m horizontal resolution were evaluated to determine the role of spatial resolution in estimating apparent outer rim diameters. The most reliable predictions were achieved using the 12 m TanDEM-X data set with an estimated error ≤16%. We then achieved an estimated error ≤8% when applying the algorithm to three Martian peak ring impact structures (Kepler, Lowell, and Lyot) using 200 m resolution DEMs, and 1%–13% when applied to a 600 m resolution DEM of the Mead multi-ringed impact structure on Venus. Our results indicated that apparent outer rim diameters of complex impact structures can be estimated using these methods with reasonable reliability, but prediction efficacy decreased with decreasing DEM vertical fidelity. Application of these methods to additional impact structures is required to quantify prediction uncertainty before applying this methodology to more recent impact structures with questionable diameters.

The rapid neutron capture process (r-process) is responsible for producing about half of the elements heavier than iron in the Universe through cataclysmic events such as core-collapse supernovae and neutron star mergers (NSMs). Despite extensive research, the exact astrophysical sites of the r-process remain one of the unanswered questions in science. The well-known supernova-produced radioisotope ⁶⁰Fe has been detected in terrestrial reservoirs, providing evidence that material from a nearby supernova reached Earth approximately 2 million years (Ma) ago. Our study reports the detection of ²⁴⁴Pu in fossilized stromatolite samples that are 2.0 Ma old, collected from palustrine–lacustrine stratigraphic layers dating back to approximately 5 Ma located at the margins of the present-day Lake Turkana Basin in northern Kenya. We demonstrate that stromatolites can mass-concentrate actinides in the range of 10²–10³. Using accelerator mass spectrometry, we isolate ²⁴⁴Pu and eliminate the anthropogenic contribution. From our findings, we evaluate a terrestrial fluence between 0.2 and 4.7 × 10³ at ​​​​cm⁻², in relative agreement with previous studies. The detection of the r-process ²⁴⁴Pu around 2 Ma ago raises the possibility of a common supernova origin with ⁶⁰Fe; however, alternative scenarios, such as the production of ²⁴⁴Pu in NSMs or other cosmic events and its transport to Earth alongside ⁶⁰Fe via interstellar debris, cannot be ruled out, highlighting the need to consider multiple mechanisms for isotopic transport in the cosmos.

We present new evidence for active coastal and oceanic features in Titan's Punga Mare observed in a high-phase Cassini Visual Infrared and Mapping Spectrometer observation of sun glint from the T110 flyby. We observe sunglint in a coastal channel, Apanohuaya Flumen, resulting from differing pixel contributions of land adjacent to the liquid-filled channel. Along the eastern shoreline, we identify a 5 μm bright margin. A possible explanation for this brightening includes a coastal margin of capillary wave fields. We find additional evidence of variegated sea surface roughness in Fundy Sinus and isolated Sun glitter near Hawaiki Insulae. RADAR observations of debouches (where rivers meet bays) within Punga Mare overlap several bright 5 μm pixels that indicate rough liquid surfaces. We postulate that a change in liquid flow regimes, possibly occurring as surface streamflow or bubble outburst events, may be responsible for surface roughness near these debouches. These observations imply air–sea–land interactions and active hydrology represented by possible streamflow are present in Titan's sea district during the northern summer.

Erg Chech 002 (EC 002), an andesitic meteorite, has been dated to be the oldest magmatic rock in the solar system. However, controversy has arisen due to inconsistent dating results and isotopic compositions in previous studies, which complicates understanding the evolution of andesitic magmatism in the early solar system. In this study, we conducted comprehensive Cr isotopic studies on two fragments of EC 002, identifying distinct nominal crystallization ages (4567.3 ± 0.8 and 4565.9 ± 0.6 Ma, respectively), as well as nucleosynthetic ⁵⁴Cr anomalies (ε⁵⁴Cr values of −1.12 ± 0.16 and −0.57 ± 0.16, respectively) and ε⁵³Cr values (−0.37 ± 0.06 and −0.06 ± 0.06, respectively). These results highlight the highly isotopically heterogeneous nature of the EC 002 meteorite. The difference in nominal crystallization ages likely reflects the initial ⁵³Mn/⁵⁵Mn heterogeneity among various EC 002 fragments. The highly isotopically heterogeneous nature of the EC 002 meteorite may be directly inherited from its surrounding nebula, suggesting subplanetesimal-scale heterogeneity of the inner solar nebula during the formation time of EC 002. We affirmed the oldest crystallization age for EC 002 among all achondrites at ∼4565.9 Ma. Previous discrepancies in dating results and isotopic compositions should arise from the isotopic heterogeneity in the EC 002 meteorite.