Journal of Geophysical Research: Planets最新文献

Extensive research over the past two decades has shown that early Mars likely had a warmer, wetter climate with widespread water activity. Ferromagnesian (Fe,Mg-rich) clay deposits are compelling markers of these ancient environments, helping reconstruct Mars' hydrologic evolution, assess past habitability, and guide future exploration. This study analyzes hyperspectral data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) aboard NASA's Mars Reconnaissance Orbiter, focusing on regions along the Martian crustal dichotomy—where clay deposits occur at the boundary between the ancient southern highlands and the younger northern lowlands. We systematically surveyed ∼1500 CRISM targeted observations (1–2.6 μm) to identify ferromagnesian clays, distinguish them from other hydrated minerals, and characterize compositional differences between Fe- and Mg-rich species using diagnostic absorptions around 1.4, 2.3, and 2.4 μm. Results reveal spatial variations in clay mineralogy: Fe-rich nontronites are prevalent around Mawrth Vallis, while Mg-rich saponites are more locally distributed in Nili Fossae and Libya Montes. Oxia Planum—the Rosalind Franklin rover landing site—exhibits more compositionally intermediate clays such as vermiculites and ferrosaponites. These differences may reflect variations in the iron and magnesium abundance or in the iron oxidation state. Moreover, a recurring absorption near 2.5 μm suggests co-occurring carbonates like magnesite and siderite, increasing the potential for biosignature preservation. These findings refine our understanding of Mars' aqueous history and offer an important mineralogical context for future rover and sample return missions. They also emphasize the need for a next-generation orbital imaging spectrometer to succeed CRISM and extend its legacy.

The fluid threshold, the wind required to move a grain from rest, is considered the critical friction velocity above which saltation begins. In this paper, the electrostatic force and the lift force of the thermal creep gas flow due to the insolation are simultaneously considered to theoretically investigate the fluid threshold of Martian grains. A model of the fluid threshold for grains saltating on the surface of Mars is derived based on the moment balance equation, which is validated with the experimental results and the prediction results of Mars Weather Research and Forecasting. It is found that the electrostatic force reduces the fluid threshold by 10.4%, and the lift force induced by insolation reduces the fluid threshold by 11.7%, and the reduction of the fluid threshold by both these forces is more significant, which enhances the dust flux by about an order of magnitude. The fluid threshold calculated by the model explains that wind-blown sand still exists at low wind speeds on Mars observed by the Viking Lander 2, Curiosity rover and Perseverance rover. In addition, the effect of insolation and electric field on the fluid threshold is more significant when the cohesion is stochastic, and the model predicts that Martian grains in micrometer size can be lifted off the surface by the electrostatic force and the lift force induced by insolation even with no wind.

On 27 December 2024, Juno's JIRAM (Jovian InfraRed Auroral Mapper) instrument observed an unprecedented volcanic event in Io's southern hemisphere, covering a vast region of ∼65,000 km², near 73°S, 140°E. Within the imaged region, only one hot spot was previously known (Pfd454). This feature was earlier estimated to cover an area of 300 km² with a total power output of 34 GW. JIRAM results show that the region produces a power output of 140–260 TW, over 1,000 times higher than earlier estimates and likely exceeding the brightest eruption ever recorded on Io, that of Surt in 2001 (∼80 TW). Three adjacent hot spots also exhibited dramatic power increases: P139, PV18, and an unnamed feature south of the main one that surged to ∼1 TW, placing all of them among the top 10 most powerful hot spots observed on Io. A temperature analysis of the features supports the simultaneous onset of these brightenings and suggests a single eruptive event propagating beneath the surface across hundreds of kilometers; this is the first time this has been observed on Io. This in turn would imply a connection among the hotspots' magma reservoirs, while other nearby hotspots that have been known to be active in the recent past, such as Kurdalagon Patera, appear unaffected. The simultaneity supports models of massive, interconnected magma reservoirs. The topology of these regional magma systems may resemble that of a large-scale sponge, in which the massive reservoirs are the pores, interconnected through a largely solid outer shell.

The escalating pace of space exploration has ushered in a new era reminiscent of the space race of the 1960s. However, the discourse on exogeoconservation—the protection of geological heritage—now demands a prominent place in decision-making processes. This paper underscores the urgency of developing research frameworks, legal regimes, and best practices to ensure sustainable and responsible exploration of extraterrestrial environments. The scientific community holds a pivotal role in quantifying the significance of these environments, safeguard the invaluable heritage of celestial bodies while allowing for responsible resource utilization, and prevent the consequences of unchecked exploration. From the point of view of the geosciences, there is an urgent need to develop tools to allow the identification of geological heritage on celestial bodies, filling a fundamental scientific gap required to establish effective exogeoconservation practices.

Martian fluvial valleys provide evidence for the surface flow of liquid water, making them a key target for rover-based investigations of ancient habitability. The Mars 2020 Perseverance rover spent ∼85 sols exploring the Bright Angel formation, exposed across the floor of Neretva Vallis: the western inlet channel of Jezero crater. This study documents the sedimentology and stratigraphy of the Bright Angel formation to reconstruct its depositional setting. The unit preserves a concave-up bedding structure consistent with a young channel-fill deposit, rather than an older unit exposed by incision of Neretva Vallis. The lower stratigraphy displays a fining-up sequence from coarse-grained sediments up to pebble-conglomerates (the Tuff Cliff member) into a ≥10-m-thick succession of laminated mudstone (the Walhalla Glades member), interpreted as a transgressive sequence recording the onset of lacustrine conditions in Neretva Vallis. Lenses of matrix-supported granule-conglomerate adjacent to the valley wall (the Fern Glen Rapids member) may preserve locally derived debris flows entering the lake. These are overlain by a polymict, matrix-supported, boulder-conglomerate (the Mount Spoonhead member), interpreted as a high-energy debrite derived from the watershed. The sequence is capped by cross-stratified sediments (the Serpentine Rapids member), preserving lake margin deposits. The Bright Angel lacustrine sequence occurs ∼10–50 m higher in elevation than the lake level anticipated for the Jezero western delta, requiring an additional period of lacustrine activity. The structure and spatial distribution of the unit leads us to propose that a late-stage blockage of Neretva Vallis may have facilitated the formation of a perched, valley-confined lake upstream.

Dust in the atmosphere of Mars, along with its radiative effects, is the central factor for understanding the Martian climate. Global circulation models and remote sensing observations are used to shed light on the evolution of Martian dust storms. Trajectories of Martian dust storms have been investigated by manual treatment of Mars daily global maps from the MARs Color Imager. However, the tracking of dust storms has neither been automated, nor systematically compared with modeled dust storm trajectories. We therefore developed a simple algorithm to detect regions with an enhanced atmospheric dust content and to attribute these regions to a trajectory. We applied this algorithm to daily global maps of measurements of the column dust optical depth for Mars Years 24–35, and found 20 dust storm trajectories lasting for at least 10 Sols. We compared these observation-based trajectories with the corresponding model-based trajectories from our own simulations using the global circulation model Mars Planetary Climate Model version 6. The obtained distributions of storm speed and direction of propagation show strong similarities between observations and model, demonstrating a reasonably good performance of the model with regard to dust storm trajectories. We find that most dust storms on Mars are traveling east- or westwards, but that dust storms propagating westwards are less well represented in the model. The developed algorithm can be used as a tool for model evaluation, but also for tracking meteorological conditions along dust storms' trajectories, allowing for further development of dust storm understanding.

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.

Magnetosonic (MS) waves, a type of plasma wave with frequencies between the proton gyrofrequency and the lower hybrid frequency, play a critical role in the dynamics of space plasma environments. This study presents a comprehensive statistical analysis of locally generated MS waves in the Martian magnetosheath and magnetosphere, based on nearly nine years of MAVEN observations (October 2014–May 2023). Using wavelet transform and singular value decomposition techniques, we identify MS wave events and investigate their spatial distribution, occurrence rates, and dependence on solar wind and solar EUV conditions. Our results reveal that locally generated MS waves predominantly occur in the nightside magnetic pileup region and magnetotail (with a northern preference), with occurrence rates reaching ∼8%. These waves exhibit dawn-dusk asymmetry, with higher rates on the dawn side. The occurrence rates increase with altitude, from ∼0% below 200 km to over 5% at 400–500 km. Solar wind dynamic pressure and solar EUV radiation strongly influence the spatial distribution and amplitude of MS waves, with high-pressure and high-EUV conditions favoring higher occurrence rates and larger wave amplitudes in the magnetotail. This study highlights the potential role of MS waves in ionospheric particle heating and escape, particularly through resonant interactions with ions. These findings underscore the complexity of MS wave dynamics in the Martian magnetosphere and their sensitivity to solar activity, providing critical insights for future studies of the plasma environment of Mars and its interaction with the solar wind.

The Martian lava plains are characterized by their extensive, low-relief surfaces, which are the result of numerous basaltic eruptions and feature a variety of volcanic landforms, including vents, cones, pits, and skylights. The combination of these features and impact craters yields a significant understanding of the planet's geological past and subsurface composition. However, the flat terrain presents a challenge to detailed morphometric analyses, while the unavailability of high-resolution Digital Elevation Models (DEMs) complicates the precise estimation of radar-based thicknesses and dielectric constants. To address these challenges, we investigated an ∼8,030 km² area northwest of Ascraeus Mons within the Tharsis Region. Prior research documented Amazonian volcanic features in this region; however, precise thickness and permittivity values remained undetermined owing to insufficient surface features and limited exposures. An enhanced, multi-scale neighborhood analysis method, adapted from terrestrial and Martian applications, was utilized to define the boundaries of a shallow lava flow sequence and identify three previously unmapped volcanic vents. Subsequently, all available subsurface sounding radar data in the region were analyzed using a simplified method. The results demonstrate that shallow, low-relief lava flows overlie a series of laterally consistent subsurface units, suggesting that volcanic and sedimentary processes occurred in multiple phases. The combination of our unique morphometric methodology using radar sounding showcases the characterization of morphologically subtle features despite the constraints of available data. This study offers a methodological framework for the investigation of other low-relief Martian regions, enhancing our understanding of the planet's volcanic and stratigraphic evolution.