Journals
2026 EN
Shearer Charles K. · McCubbin Francis M. · Hendrix Amanda
Abstract The Artemis Program will return a variety of lunar samples from regions of the Moon that are thus far unexplored by human surface activities. Are we ready? As a first step in preparing for Artemis, NASA initiated the Apollo Next Generation Sample Analysis (ANGSA) program that involved the study of a unique suite of samples returned by the Apollo 17 mission to the Taurus Littrow Valley but never opened. These samples included a core sample sealed on the surface of the Moon and samples stored, curated, and studied under cold conditions. Analyses of these samples were conducted by an international team of scientists and engineers within the framework of a new human sample return mission to the TLV. This mission integrated boots‐on‐the‐ground observations by Apollo 17 astronaut Harrison Schmitt, orbital data from recent missions, preliminary examination utilizing both established and innovative approaches, and sample analyses using a variety of proven and advanced technologies. ANGSA accomplished many firsts in lunar exploration, science, and curation. For example, the ANGSA initiative opened the first sealed Core Sample Vacuum Container; conducted the first examination of a core penetrating a landslide deposit; completed the first experiment to sample endogenous gases released from the Moon's interior (via the Lee‐Lincoln scarp); examined the water content of terrestrial uncontaminated lunar regolith; and cold‐curated and cold‐processed Apollo samples for almost 50 years. The manuscripts in this special issue highlight these and other observations and resulting discoveries.
Journals
2026 EN
David G. · Barucci A. · Lasue J.
+6 more
Abstract The forthcoming MMX (Martian Moon eXploration) mission will carry the MIRS instrument (MMX Infrared Spectrometer) to study the composition of the Martian system. On airless bodies, like Phobos and Deimos, micrometeorite bombardment can strongly modify the spectral properties of their surface materials. To better identify the effects of micrometeorite bombardment on infrared spectroscopy data, we have simulated, using nanosecond pulse‐laser irradiation experiments, micrometeorite impacts on minerals and rock relevant for the surface composition of Phobos and Deimos based on our current knowledge. Laser irradiation was performed on pure mineral phases (i.e., nontronite, antigorite, biotite, goethite) and basalt, and their reflectance spectral properties were acquired between 0.5 and 3.6 μm. Our results reveal that laser impacts can reduce the strength of specific absorption bands characteristic of these minerals. In addition, laser impacts can also significantly modify the position of specific absorption bands, especially for phyllosilicates. Iron features originally near 0.65–0.75 μm, and the∼ ${\sim} $ 2.8 μmH 2$}_{2}$ O/OH bands are the most affected. They can shift up to a few tens of nanometers toward shorter or longer wavelengths, depending on the sample. The overlap between the iron band positions (e.g., between altered antigorite and pristine nontronite) suggests that space weathering can distort the accurate identification of minerals using infrared spectroscopy. Finally, we observed that the signature of antigorite subjected to micrometeorite bombardment is close to the signature observed on Phobos with CRISM data. Therefore, we believe that this mineral should be seriously considered as a potential constituent of the Phobos regolith.
Journals
2026 EN
Jones Alexander J. · Gupta Sanjeev · Barnes Robert
+27 more
Abstract Martian carbonate‐bearing rocks are compelling targets for exploration because they preserve detailed records of past aqueous processes, climate, and habitability. The Margin unit in Jezero crater is a distinct olivine‐ and carbonate‐bearing unit stratigraphically underlying the western fan, lining the inner margin of the western crater rim and has a contested origin. Perseverance spent ∼350 sols investigating the unit as part of its fourth mission campaign, aiming to constrain its origin, alteration history and biosignature preservation potential. This study reports on the lithofacies and stratigraphy of the unit by analyzing Mastcam‐Z mosaics and derived 3D outcrop models, supplemented by long‐distance SuperCam observations and detailed textural analyses from SHERLOC WATSON and ACI images. We find that the Margin unit comprises two distinct sub‐units. The Eastern Margin Unit (EMU) comprises well‐stratified, low‐angle basinward‐, rimward‐ and sub‐horizontally inclined medium‐grained sandstones which preserve angular to rounded grains, occasional cross‐stratification, convex‐up bedding, and erosion surfaces. The Western Margin Unit (WMU) comprises distinctly structureless to decimeter‐scale parallel‐layered rocks which drape the crater rim and are inclined into the crater. The origin of the WMU is uncertain but may be most consistent with a variably carbonated olivine cumulate. The favored depositional model for the EMU is a lacustrine shore zone environment where sediments derived from the adjacent WMU have been locally reworked by wave action along a paleoshoreline at around –2,400 m elevation. These observations suggest that the Margin unit preserves diverse subsurface and surface aqueous environments and further extends the habitability window at Jezero crater.
Journals
2026 EN
Qin Yu · Gong Shengxia · Liao Xinhao
Abstract The structure of the lunar crust preserves key records of the Moon's origin and long‐term evolution. Using the latest high‐resolution gravity field from the Gravity Recovery and Interior Laboratory (GRAIL) mission together with Lunar Orbiter Laser Altimeter (LOLA) topography, we investigate the shallow crustal structure of the lunar farside. Applying the effective density spectrum technique with a two‐layer formulation, we constrain the densities of the upper and lower layers and the depth of their interface. Our results reveal a thin (average 4.7 km), low‐density (average 2,111 kg m − 3$-3}$ ) surficial layer, likely representing a highly porous megaregolith formed by basin ejecta and impact fragmentation, overlying a higher density unit (average 2,739 kg m − 3$-3}$ ) consistent with a less porous, anorthositic crust. From the inferred upper‐layer density, we estimate crustal porosity and find that the porosity decreases systematically with increasing interface depth, while exhibiting substantial lateral variability at a given depth. This variability is closely linked to differences in cumulative impact modification. Residual porosity below ∼2 km shows a statistically significant negative correlation with N(20), indicating that repeated small impacts have progressively compacted the shallow crust and reduced its pore space.
Journals
2026 EN
Fine A. · Poggiali V. · Lalich D.
+1 more
Abstract Undifferentiated plains are the most common terrain type on Titan, yet their composition and geologic history remain poorly understood. To better characterize their physical properties, we combined Cassini RADAR measurements from nadir altimetry and side‐looking SAR modes. We analyzed these data using radar backscatter models, finding that the multi‐angle radar response from undifferentiated plains across Titan is remarkably consistent. This uniformity suggests globally similar properties and formation processes, permitting aggregate modeling. Our analysis reveals that canonical single‐layer scattering models fail to reproduce the observed backscatter, particularly the bright near‐nadir returns captured by altimetry, which proved critical for model discrimination and accurate parameter estimation. Instead, a two‐layer model is required to fit the data across all incidence angles. Best‐fit parameters indicate undifferentiated plains likely consist of a highly porous, low‐density surface layer (effective permittivity 1.33) that is exceptionally smooth at radar wavelengths (RMS slope 2°), overlying a higher‐density (effective permittivity >2.7) and rougher buried substrate. This surface layer is likely less than 1 m thick. The layered structure, along with the observed global uniformity and extreme flatness at multiple scales, is most consistent with long‐term atmospheric deposition of organic particles (“tholin snow”), which are subsequently densified or buried, potentially during periods of different environmental conditions. The structure of the undifferentiated plains provides insights into organic processing and transport on Titan and potentially preserves a record of past environmental conditions. Measurements made by the upcoming Dragonfly mission may provide answers to questions raised by our analysis.
Journals
2026 EN
Dahmen Nikolaj L. · Clinton John F. · Stähler Simon C.
+2 more
Abstract NASA's InSight mission has provided an unprecedented snapshot of Mars' seismicity, despite data analysis challenges arising from low signal‐to‐noise ratios (SNR) and single‐station constraints. High frequency (HF) events—the most common type—were initially assumed to propagate through shallow crustal layers. However, several impacts that occurred late in the mission provided independent distance constraints, indicating that HF event energy must have propagated through the mantle. We analyzed the full HF data set using an extended catalog and denoised waveforms derived with deep learning (DL) techniques. Using a DL ensemble, we picked phase arrivals on denoised envelopes and estimated SNR‐dependent pick timing uncertainties based on the removed noise. We computed distances consistent with mantle paths using the latest Mars interior models, while the back azimuth remained inconclusive due to local resonance dominating the HF bandwidth. We compared and grouped HF recordings by their similarity and investigated how attenuation properties shape their envelopes. Additionally, we re‐calibrated and assigned magnitudes for the extended catalog. Overall, we (re‐)located 1,430 HF events clustered between epicentral distances of around 1,600–3,600 km, but without constraints on the back azimuth, their source region remains speculative. Based on spatiotemporal similarities, we attributed a subset of 1,357 events to a common source region and labeled them as swarm events. The analysis of envelope shape confirms and extends previous results of stratified attenuation properties. Swarm events, with magnitudes between 1.5 and 2.5, are cumulatively equivalent to a single magnitude 4 event and show a highb $b$ ‐value and clear seasonal trends in seismicity.
Journals
2026 EN
Baijal Namya · Asphaug Erik · Denton C. Adeene
+5 more
Abstract Asteroid (16) Psyche, the largest member of the M/X‐type asteroids, may be the leftover core of a differentiated planetesimal. As such (16) Psyche will be explored in detail by NASA's discovery‐class Psyche mission in 2029. This will be the first mission to orbit a metal‐rich asteroid, or any asteroid in the 100–500 km size range. A key unresolved question, and the primary objective of the mission, is to infer whether Psyche is a core or a primordial, unmelted object. One way to constrain an asteroid's interior is through the study of its largest basins and how that affects its morphology, depth‐to‐diameter ratio, and surface distribution of metal. Here, in preparation for the mission, we model the impact formation of a significant basin at Psyche's north pole, identified in ground‐based imaging. Using high‐resolution Smoothed Particle Hydrodynamics simulations applied to the asteroid's 3D shape, we show how modeling the formation of Psyche's impact basins will constrain its interior through comparison with mission observations and may allow us to infer whether Psyche has a core. We adopt two end‐member interior structures: a differentiated target with a metal core and mantle, and a mixed rock‐metal homogeneous target. We demonstrate the formation of the polar crater for both end‐members, and how Psyche's porosity and strength influence the depth‐diameter ratio, the final crater morphology, and the expected simple‐complex crater transition.
Journals
2026 EN
Drilleau Mélanie · Samuel Henri · Verhoeven Olivier
+4 more
Abstract Understanding Mars' deep interior is essential to reconstruct its geological history, thermal evolution, and present‐day dynamics. To this end, the NASA InSight mission has provided unprecedented seismic observations. However, strong trade‐offs between temperature and composition in seismic interpretations continue to limit our ability to resolve interior models. To address this challenge, we account for electromagnetic induction data from Mars Global Surveyor as an additional, independent constraint. We develop a joint probabilistic inversion framework that simultaneously fits seismic body wave arrival times, electrical conductivity, thek 2${k}_{2}$ Love number, and the moment of inertia. A key feature of our approach is the integration of Mars' long‐term thermal evolution within the forward model, along with mineral physics and petrology data, to better constrain geodynamical parameters. We explore three different mantle compositions (Sanloup et al., 1999, https://doi.org/10.1016/s0031‐9201(98)00175‐7 ; Taylor, 2013, https://doi.org/10.1016/j.chemer.2013.09.006 ; Yoshizaki & McDonough, 2020, https://doi.org/10.1016/j.gca.2020.01.011 ) and consider both radially homogeneous and heterogeneous (with a basal molten layer (Samuel et al., 2023, https://doi.org/10.1038/s41586‐023‐06601‐8 )) mantle scenarios. For homogeneous mantle models, two families of solutions emerge regardless of the bulk composition: one with low Mg content and high potential temperature, which better reproduces electrical conductivity data due to a thicker lithosphere, and another with high Mg content and lower potential temperature. Models with a heterogeneous mantle reproduce electrical conductivity data less accurately, due to thinner lithospheres, and the mantle composition of Yoshizaki and McDonough (2020, https://doi.org/10.1016/j.gca.2020.01.011 ) appears to be less consistent with the full data set. To further refine models of Mars' interior, future efforts should focus on acquiring electromagnetic data with reduced uncertainties and seismically constraining more precisely the depth of mantle discontinuities associated with mineral phase transitions.
Journals
2026 EN
Cambioni Saverio · Weiss Benjamin P. · Baijal Namya
+12 more
Abstract Asteroid (16) Psyche is the largest likely metal‐rich asteroid in the Solar System and the target of the NASA Psyche mission. The mission aims to determine whether the asteroid is the core of a differentiated planetesimal that lost its mantle via a giant impact. To prepare for spacecraft observations of the asteroid, we combine impact and geodynamic models to predict the magnetization, composition, and interior structure of a mantle‐stripped core with the mass and density of Psyche. We show that Psyche‐like bodies can form from a single giant impact, with a hit‐and‐run collision being the most likely scenario. After the impact, Psyche's materials could have become magnetized while cooling in a dynamo field generated by its advecting core and/or in the magnetic field of the solar nebula. The former is diagnostic of Psyche being a mantle‐stripped core and is favored if Psyche's primordial sulfur content and current metal content are≳ $\gtrsim $ 10 wt.% and≳ $\gtrsim $ 50 wt.%, respectively. A sulfur content≳ $\gtrsim $ 10 wt.% delays core solidification long enough for kamacite in the asteroid's exterior to cool through the Curie temperature while the dynamo is still active. Formation of Psyche analogs with≳ $\gtrsim $ 50 wt.% metal content requires highly energetic impacts that more favorably occur after nebular‐gas dissipation. Therefore, if the Psyche spacecraft's Magnetometer, Gamma‐Ray Neutron Spectrometer, and Gravity and Topography Investigations respectively measure strong ( > 2 × 1 0 14${ >} 2 1{0}^{14}$Am 2${\text{Am 2}$ ) magnetization, sulfur‐rich surface provinces compatible with a bulk primordial sulfur content≳ $\gtrsim $ 10 wt.%, and metal content≳ $\gtrsim $ 50 wt.%, Psyche most likely formed as a mantle‐stripped core.
Journals
2026 EN
Silva J. E. · Peralta J. · Imamura T.
+7 more
Abstract We present new detections of mesoscale stationary features, which are interpreted as gravity waves, on the dayside clouds of Venus. These come from an analysis of images from two instruments onboard different spacecrafts: Visible and InfraRed Thermal Imaging Spectrometer—Mapper (VIRTIS‐M) on Venus Express (VEx) and IR2 on Akatsuki. For VIRTIS‐M we selected the period from the first extension of the mission (roughly from August 2007 to May 2009). The wavelength range selected was based on best viewing conditions to characterize waves, centered at 600 nm. For IR2 we surveyed the entire available data at 2.02 μm targeting the dayside hemisphere. Basic morphological properties of the detected features were retrieved, namely their horizontal wavelength, packet sizes and orientations. Our measurements show that the horizontal wavelengths of these features are between 100 and 500 km, their widths between 500 and 3,000 km, and mostly oriented so that the crests align with the local meridian. We also retrieve the background wind in the vicinity of the detected structures to then calculate the vertical wavelength. The inclusion of the vertical wind shear of the zonal wind at the altitudes where these waves are observed proved significant in these calculations. For the features from Akatsuki data, we find values in good agreement with previous works however, for VIRTIS‐M their dimensions appear slightly reduced. This works aims to expand the current knowledge of the distribution of stationary waves with further applications to understand dynamical connections between the surface and the cloud layer in Venus' atmosphere.