The margin of Chryse Planitia, Mars, contains >105 kilometre‐scale mesas, buttes, and plateaus (‘mounds’), many of which are found in and around Oxia Planum—the ExoMars 2022 Rover landing site. Despite this, their origins and evolution are unknown. We have analysed the morphologies and morphometries of 14,386 individual mounds to: 1) classify them based on their geomorphology; 2) constrain when they

The lunar mascon basins are characterized by high gravity anomalies and thin crust. Study of the density structure beneath the mascon basins can help to understand the origin of these gravity anomalies and infer their formation and evolution. We propose an efficient forward gravity method based on the 3‐D Gauss‐Legendre quadrature (GLQ) and Fast Fourier Transforms (FFT) combined with the adaptive discretization

We investigate the dynamics of a water pumping mechanism driven by temperature variations in the lunar subsurface. The thermal environment at three polar sites and three sites in the Clavius region was simulated taking into account local terrain and scattered radiation. A separate heat and mass transfer model was used to simulate depth‐, temperature‐ and pressure‐dependent properties of the lunar subsurface

The south polar layered deposits of Mars contain a massive CO2 ice reservoir formed during periods of low planetary obliquity and partial atmospheric collapse. Within the reservoir are bounding layers (BLs) that are believed to consist entirely of water ice and modify CO2 ice stability during periods of higher obliquity and insolation. Here we use 3‐D data from the Shallow Radar instrument to extend

Mars’ controversial hypothesized ocean shorelines have been found to deviate significantly from an expected equipotential surface. While multiple deformation models have been proposed to explain the wide range of elevations, here we show that the historical locations used in the literature and in these models vary widely. We find that the most commonly used version of the Arabia Level does not follow

No abstract is available for this article.

The physical processes during planet formation span a large range of pressures and temperatures. Giant impacts, such as the one that formed the Moon, achieve peak pressures of 100s of GPa. The peak shock states generate sufficient entropy such that subsequent decompression to low pressures intersects the liquid‐vapor phase boundary. The entire shock‐and‐release thermodynamic path must be calculated

Organic salts, such as Fe, Ca, and Mg oxalates and acetates, may be widespread radiolysis and oxidation products of organic matter in Martian surface sediments. Such organic salts are challenging to identify by evolved gas analysis but the ubiquitous CO2 and CO in pyrolysis data from the Sample Analysis at Mars (SAM) instrument suite on the Curiosity rover indirectly points to their presence. Here

Modeling the planetary heat transport of small bodies in the early Solar System allows us to understand the geological context of meteorite samples. Conductive cooling in planetesimals is controlled by thermal conductivity, heat capacity, and density, which are functions of temperature (T). We investigate if the incorporation of the T‐dependence of thermal properties and the introduction of a nonlinear

Recent work used the kinetic theory of molecular gases, along with state‐of‐the‐art intermolecular potentials, to calculate from first principles the diffusivity ratios necessary for modeling kinetic fractionation of water isotopes in air. Here, we extend that work to the Martian atmosphere, employing potential‐energy surfaces for the interaction of water with carbon dioxide and with nitrogen. We also

Observations of exoplanet atmospheres have shown that aerosols, like in the solar system, are common across a variety of temperatures and planet types. The formation and distribution of these aerosols are inextricably intertwined with the composition and thermal structure of the atmosphere. At the same time, these aerosols also interfere with our probes of atmospheric composition and thermal structure

Lithified aeolian strata encode information about ancient planetary surface processes and the climate during deposition. Decoding these strata provides insight regarding past sediment transport processes, bedform kinematics, depositional landscape, and the prevailing climate. Deciphering these signatures requires a detailed analysis of sedimentary architecture to reconstruct dune morphology, motion

Discerning the total mass of Mars’ obliquity‐timescale (∼105‐year) exchangeable CO2 inventory has been elusive for decades due to the unknown adsorptive capacity of its regolith. Now, however, the stratigraphy of Mars’ recently discovered South Polar Massive CO2 Ice Deposit (MCID) provides a record of orbit‐driven CO2 exchange between its polar cap, atmosphere, and regolith with sufficient constraint

Maps of plagioclase, olivine and pyroxene at 1 km resolution are derived from a combination of data from the Diviner Lunar Radiometer on the Lunar Reconnaissance Orbiter and the Kaguya Multiband Imager. The Diviner instrument features three infrared bands designed to characterize a spectral feature of lunar soils that is sensitive to the average silica polymerization of the surface called the Christiansen

Since February 2019, NASA's InSight lander is recording seismic signals on the planet Mars, which, for the first time, allows to observe ongoing tectonic processes with geophysical methods. A number of Marsquakes have been located in the Cerberus Fossae graben system in Elysium Planitia and further west, in the Orcus Patera depression. We present a first study of the focal mechanisms of three well‐recorded

Based on the previous applications of laser altimetry to planetary geodesy at GSFC, we use the recently developed PyXover software package to analyze altimetric crossovers from the Mercury Laser Altimeter (MLA). Using PyXover, we place new constraints on Mercury's geodetic parameters via least squares minimization of crossover discrepancies. We simultaneously solve for orbital corrections for each

Interactions among the thermal tide, airborne dust, and water ice clouds significantly influence the Martian atmosphere. The absence of a stratosphere on Mars allows easier identification of the thermal tides from observational data than that on Earth, making Mars a natural laboratory to study the tidal excitation and propagation processes. However, the global tidal phase structure and its response

Ozone (O3) in the atmosphere of Mars is produced following the photolysis of CO2 and is readily destroyed by the hydrogen radicals (HOx) released by the photolysis and oxidation of water vapor. As a result, an anti‐correlation between ozone and water vapor is expected. We describe here the O3‐H2O relationship derived from 4 Martian years of simultaneous observations by the SPICAM spectrometer onboard

We report the impact of the 2018 Mars global dust storm on the ionosphere, in particular, its peak altitude during the onset and growth phases of the event. A one‐dimensional photochemical model is applied to estimate the ionospheric electron densities below 200 km using the measurements of in situ neutral densities and ionizing solar radiation by the NASA Mars Atmosphere and Volatile EvolutioN (MAVEN)

Recent Mars Atmosphere and Volatile EvolutioN (MAVEN) observations have shown unexpectedly large deuterium Lyman‐α emissions near the Martian southern summer solstice. The deuterium Lyman‐α brightness can reach ∼10% of the hydrogen Lyman‐α brightness below 200 km. In this study, we propose a method to estimate the D/H ratio in the Martian upper atmosphere through analysis of the Lyman‐α vertical profiles

We analyze Mars Climate Sounder temperature and aerosol data in the tropics, and use Fourier analysis at different local times to study atmospheric tides and their relation to the dust and water ice distributions. Our results reveal that Mars year (MY) 29 has large amplitude non‐migrating thermal tides during southern hemisphere spring equinox that are not observed at the same local time in any other

Peer reviewing is the selfless act of evaluating and providing feedback on scientific papers submitted in journals like JGR: Planets. Every review is written with the objective of clarifying the article and often contains suggestions for additional analyses or topics of discussion. Reviewers often spend hours examining the rigor of the methods, the validity of the results, and the significance of the

Based on the measurements from Radio and Plasma Wave Science instrument onboard the Cassini spacecraft over 13 years, we perform a statistical analysis of electron cyclotron harmonic (ECH) wave spatial distribution in Saturn's magnetosphere. The wave occurrence rates, amplitudes, and peak frequencies as functions of magnetic local time, L‐shell, and magnetic latitude are investigated in detail. Our

Recent acquisition of high‐resolution satellite imagery of the Martian surface has permitted landslides to be studied on a global scale on Mars for the first time. We apply the Scoops3D software package to compute slope stability for select regions of the Martian surface, combining calculations of slope stability with number of observed landslides Crosta et al., 2018a, as reported in a recently published

Most of the large rocky bodies in the solar system display evidence of past and/or current magnetic activity, driven by thermochemical convection in an electrically conducting fluid layer. The discovery of a large number of extrasolar planets motivates the search for magnetic fields beyond the solar system. While current observations are limited to providing planetary radii and minimum masses, studying

The impact melt that records the formation time of basins is essential for the understanding of the lunar bombardment history. To gain a comprehensive picture of the melt distribution on the Moon, this study investigates the impact mixing of small craters based on a newly developed numerical model using the Monte Carlo method and integrates the obtained mixing behavior into the previous larger scale

Mars possesses dynamical features called polar vortices: regions of cold, isolated air over the poles circumscribed by powerful westerly jets which can act as barriers to transport to dust, water, and chemical species. The 2018 Global Dust Storm was observed by multiple orbiters and offers a valuable opportunity to study the effects of such a storm on polar dynamics. To this end, we assimilate data

Although lunar soils contain rock and mineral components from the breakdown of a mixture of rock types, a classification based on the abundances of the major silicate minerals plagioclase, olivine, low‐Ca pyroxene (LCP) and high‐Ca pyroxene can be used to evaluate the major compositional classes that are represented within a given soil. We studied the compositional classes for Apollo 15, 16 and 17

Terrestrial‐type planetary cores are thought to be predominantly composed of Fe with varying amounts of lighter chemical species or impurities chosen from a narrow range of possible elements, which includes S. These impurity elements may contribute significant effects to the transport properties of these cores, which have direct influence over dynamo and thermal evolution of the planetary body. Recent

Venus tessera terrain contains the oldest rocks preserved on the surface of the planet. The composition of the tesserae is unknown, but recent observations of near‐infrared emissivity from orbit suggest that they are silica rich. This contrasts with previous interpretation that silica‐rich rheologies are too weak to produce tessera folds. We examine the range of compositions consistent with the observed

The equilibrium thermodynamics of Fe/Mg‐phyllosilicates and carbonates have been investigated using numerical modeling, with emphasis on the effects of evaporation and temperature (hydrothermalism) under conditions related to present‐day and primitive Mars, that is, low or high CO2 partial pressure, under oxidizing or reducing environments. Findings are discussed in relation to alteration and weathering

Constraining the volatile budget of the lunar interior has important ramifications for models of Moon formation. While many early and previous measurements of samples acquired from the Luna and Apollo missions suggested the lunar interior is depleted in highly volatile elements like H, a number of high‐precision analytical studies over the past decade have argued that it may be more enriched in water

We report the aeolian changes observed in situ by NASA’s InSight lander during the first 400 sols of operations: granule creep, saltation, dust removal and the formation of dark surface tracks. Aeolian changes are infrequent and sporadic. However, on sols when they do occur, they consistently appear between noon to 3 pm, and are associated with the passage of convective vortices during periods of high

Since its recognition as an impact structure 60 years ago, no volcanics were anticipated in the circular depression of the 14.8 Ma old Nördlinger Ries. Here, we describe for the first time a volcanic ash‐derived clinoptilolite‐heulandite‐buddingtonite bed within the 330 m thick Miocene lacustrine crater fill. Zircon U‐Pb ages of 14.20 ± 0.08 Ma point to the source of the volcanic ash in the Pannonian

New analyses of Cassini radar altimeter data (Poggiali et al., 2020, https://doi.org/10.1029/2020JE006558) measure the 85 m depth and “brackish” (moderately ethane‐poor) composition of Moray Sinus, an estuary at the northern margin of Titan's largest sea, Kraken Mare. No bottom echo was detected on Kraken itself, suggesting it is either very deep, ethane‐rich, or both.

Although Mars does not possess a global magnetic field today, regions of its crust are strongly magnetized, consistent with an early dynamo, likely powered by rapid heat flow from the core. If the core is undergoing crystallization, the associated compositional changes would provide an additional mechanism for driving convection—probably the dominant driver for Earth's dynamo today. This raises the

Jupiter’s Great Red Spot (GRS), a giant anticyclone, is the largest and longest‐lived of all the vortices observed in planetary atmospheres. During its history, the GRS has shrunk to half its size since 1879, and encountered many smaller anticyclones and other dynamical features that interacted in a complex way. In 2018–2020, while having a historically small size, its structure and even its survival

Fine‐scale (submillimeter to centimeter) depositional and diagenetic features encountered during the Curiosity rover’s traverse in Gale crater provide a means to understand the geologic history of Vera Rubin ridge (VRR). VRR is a topographically high feature on the lower north slope of Aeolis Mons, a 5‐km‐high stratified mound within Gale crater. We use high spatial resolution images from the Mars

The thickness of Europa's icy shell, which controls its thermal and rheological structure, cannot currently be directly measured. However, it can be estimated through indirect methods, including geodynamic modeling. We simulate the crystallization of the ice shell from a liquid water ocean and its subsequent thermal equilibration in the presence of tidal heat. We evaluate the effects of solid‐state

The evolution of a single raindrop falling below a cloud is governed by fluid dynamics and thermodynamics fundamentally transferable to planetary atmospheres beyond modern Earth's. Here, we show how three properties that characterize falling raindrops—raindrop shape, terminal velocity, and evaporation rate—can be calculated as a function of raindrop size in any planetary atmosphere. We demonstrate

Attempts to constrain the accretion history of Mars using geochemical observations have focused on the chronology of core formation. However, given the possibility of incomplete metal‐silicate equilibration, most previous results cannot distinguish between the following two scenarios: (1) Mars was formed early through gradual accretion and remained isolated as a “planetary embryo” and (2) Mars underwent

Aeolian features at Oxia Planum—the 2023 landing site for the ExoMars Rosalind Franklin Rover (ERFR)—are important for Mars exploration because they record information about past and current wind regimes, sand transport vectors, and lend insight to the abrasion, deposition, and transport of granular material. To characterize the wind regime and erosional history of Oxia Planum we used a combination

The highly modified surface of Europa’s ice shell hides a global, salty ocean that may hold conditions favorable for life, and cycles in the ice shell likely impact those conditions by allowing material transfer between the surface and subsurface ocean. The Galileo spacecraft observed a number of young geologic features that indicated Europa’s ice shell was recently or presently active, including lenticulae

Paleolake deposits offer a valuable record for constraining ancient Martian environments and climate. Gale crater provides extensive evidence for a long and complex history of lakes; however, the exact timing, source of water, and climate under which these large lakes persisted are still unclear. We examined the geomorphology and mineralogy of Garu crater, an ∼30 km diameter crater ∼150 km to the east

Since early February 2019, the SEIS (Seismic Experiment for Interior Structure) seismometer deployed at the surface of Mars in the framework of the InSight mission has been continuously recording the ground motion at Elysium Planitia. In this study, we take advantage of this exceptional data set to put constraints on the crustal properties of Mars using seismic interferometry (SI). To carry out this

The InSight Mission began acquiring the first seismic data on Mars in early 2019 and has detected hundreds of events. The largest events recorded to date originate at Cerberus Fossae, a young volcanic region characterized by high volume, low viscosity lava flows. A handful of Low Frequency (LF) quakes that share key attributes of Long Period quakes recorded on Earth's volcanoes are also traced to Cerberus

No abstract is available for this article.

Water ice clouds form in the mesospheres of terrestrial planets in the solar system (and most likely elsewhere) by vapor deposition at low pressures and temperatures. Under these conditions a range of crystalline and amorphous phases of ice might form. The phase is important because it influences nucleation kinetics, density, vapor pressure over the solid, growth rates and particle shape. In the past

Impact crater records on planetary surfaces are often analyzed for their spatial randomness. Generalized approaches such as the mean second closest neighbor distance (M2CND) and standard deviation of adjacent area (SDAA) are available via a software tool but do not take the influence of the planetary curvature into account in the current implementation. As a result, the measurements are affected by

Numerous types of activity in mid latitude martian gullies have been observed over the last decade. Some activity has been constrained to occur in the coldest times of year, suggesting that surficial frosts that form seasonally and diurnally might play a key role in this activity. Here we use thermal infrared data to explore the global, spatial and temporal variation of temperatures conducive to CO2

The nighttime ozone and sulfur dioxide distributions were analyzed using the entire Spectroscopy for the Investigation of the Characteristics of the Atmosphere of Venus (SPICAV) UV/Venus Express stellar occultation data set. After the discovery of an ozone layer at 100 km in the mesosphere reported by Montmessin, Bertaux, et al. (2011, https://doi.org/10.1016/j.icarus.2011.08.010), 132 other detections

We have analyzed mass wasting features, their distribution and deposit geometry on the two largest main asteroid belt objects—protoplanet Vesta and dwarf planet Ceres—and compared their geomorphology and mobility. Both asteroids have similar surface accelerations, but different surface compositions. Based on our observations and previous studies, we categorized three distinct morphological mass wasting

Active aeolian systems are present across the martian surface, with active dune fields commonly found in depressions such as craters and valleys. There are many dune fields within the equatorial region of Mars, including Valles Marineris, but the effects of topography on wind regimes and consequently dune migration in Valles Marineris is poorly understood. We investigated both the ripple and dune migration

NASA's Magellan mission revealed that many Venus highlands exhibit low radar emissivity values at higher altitudes. This phenomenon is ascribed to the presence of minerals having high dielectric constants, produced or stabilized by temperature‐dependent chemical weathering between the rocks and the atmosphere. Some large volcanoes on Venus have multiple reductions of radar emissivity at varying altitudes

The origin of the interstellar object 1I/‘Oumuamua, has defied explanation. In a companion paper (Jackson & Desch, 2021), we show that a body of N2 ice with axes 45 m × 44 m × 7.5 m at the time of observation would be consistent with its albedo, non‐gravitational acceleration, and lack of observed CO or CO2 or dust. Here we demonstrate that impacts on the surfaces of Pluto‐like Kuiper belt objects

The origin of the interstellar object 1I/‘Oumuamua has defied explanation. We perform calculations of the non‐gravitational acceleration that would be experienced by bodies composed of a range of different ices and demonstrate that a body composed of N2 ice would satisfy the available constraints on the non‐gravitational acceleration, size and albedo, and lack of detectable emission of CO or CO2 or

In this study, three simulations by the Mars Weather Research and Forecasting Model are compared: two 10 Martian year (MY) 2° × 2° simulations with (i) fully radiatively active dust and (ii) a prescribed dust scenario, and a (iii) 1 MY 0.5° × 0.5° simulation with prescribed dust as in (ii). From comparing (i) and (ii), we found that the impact of dust‐radiation feedback is individually different for

Quantifying the water in all Martian water reservoirs is important for understanding the history of water on Mars, including Mars’ past climate and potential for habitability. Hydrated minerals are widespread on Mars and may comprise a significant portion of the water inventory. We calculated the possible volumes of water stored within and required to form hydrated minerals on Mars by estimating the

During the exploration traverse of the Von Kármán crater on the lunar farside, the Yutu‐2 rover, part of China's Chang'e‐4 mission, come across rock fragments with higher albedo than the surrounding surface. This study investigates their origin, emplacement, and composition based on in situ spectral analysis and geological considerations. The spectral signatures of two fragments show a clear dominance

The CheMin instrument on the Mars Science Laboratory rover Curiosity detected ubiquitous high abundances (∼15–70 wt%) of X‐ray amorphous components (AmCs) in ancient sedimentary rocks of Gale crater. Mechanisms and timing of formation for the AmCs are poorly constrained, and could include volcanic, impact, or aqueous processes. We explore trends in AmC composition and abundance, and look for systematic