Journal of Geophysical Research: Planets最新文献

The lunar south polar region has been a focus of human exploration due to its potential rich water-ice and mineral resources. However, scientific exploration of this area based on spectral data is limited due to challenging lighting conditions and complex topography. In this work, we used the Moon Mineralogy Mapper (M³) and Lunar Orbiter Laser Altimeter (LOLA) reflectance data to construct a hyperspectral cube in the lunar 83°–90°S region. Mineralogical abundance maps of the four major lunar minerals were derived from M³ data at a spatial resolution of ∼193 m/pixel. Quantitative mineral maps of four common lunar minerals, including high-calcium pyroxene (HCP), low-calcium pyroxene (LCP), olivine, and plagioclase, were derived from the M³ data, with abundance ranges consistent with those from the Kaguya Spectral Profiler (SP) data. The high-resolution mineral maps enhance the identification of mineral distribution details, such as purest anorthosite enrichment in the crater wall and floor of the Shackleton Crater. Comprehensive analysis of the mineral abundance maps reveals geological characteristics and potential effects of impact events, with particular emphasis on Artemis III mission landing site candidates. Pyroxene enrichment detected in the De Gerlache-Kocher Massif region may present an opportunity to collect South Pole-Aitken ejecta materials.

Fluid-assisted metasomatism was prevalent on Vesta, but the timing and source(s) of aqueous activities remain elusive. Here, we report an absolute ²⁰⁷Pb/²⁰⁶Pb isochron age (4,169 ± 85 Ma) of apatites from a plagioclase-rich eucrite clast within the Jikharra 001 eucrite. Petrographic, mineralogical, and geochemical characteristics demonstrate that apatite veins in the clast formed during fluid-assisted metasomatism on Vesta. The elevated ⁸⁷Sr/⁸⁶Sr ratios observed in the bulk clast and plagioclase grains suggest the incorporation of fluid from primitive sources, probably carbonaceous chondrites. The slightly negative oxygen isotopic composition (Δ¹⁷O = −0.275 ± 0.013‰) of the clast further indicates a largely carbonaceous chondrite source. Impacts from carbonaceous chondrites are the probable origin of Veneneia. Evidence from apatite veins in the Jikharra 001 is consistent with a carbonaceous fluid source and may constrain the age of Veneneia to the late heavy bombardment, approximately 4.1–4.2 Ga.

Atmospheric hydrogen chloride (HCl, or hydrochloric acid) has strong links to volcanic activity on Earth. If it is present in the atmosphere of Mars, it could hint at active magmatic processes, or the outgassing from the remnants of recently dormant volcanoes. It has been sought in the Martian atmosphere using terrestrial telescopes and was a target for the ExoMars Trace Gas Orbiter (TGO) mission. Since it was found by TGO, the terrestrial telescopes have returned to their hunt, and the recent study by Faggi et al. (2025), https://doi.org/10.1029/2025je009105 presents the results of a multi-year campaign to study the global distribution of HCl across the Martian surface. In this commentary, we will examine the importance of HCl, its context in the broader chloride cycle on Mars, how we have gotten to this point, and the implications the new study has on our understanding of its origins.

Impact-generated hydrothermal systems are considered potentially habitable environments on Mars, Earth, and other planetary bodies for microbial life. However, there is an ongoing debate regarding what geological features on Mars provide definitive evidence for such systems. Although earlier studies have modeled hydrothermal processes in Martian craters, they often lacked integration with shock physics hydrocodes to constrain initial impact conditions. The importance of this two-code coupling was demonstrated by successfully replicating alteration signatures in the Earth's Haughton impact structure. In this study, we use a similar two-code approach, combining the iSALE hydrocode with the HYDROTHERM hydrothermal model to simulate the full evolution of impact-generated hydrothermal systems. We apply this method to craters the size of Jezero (∼50 km) and Gale (∼154 km) in diameter. Although Jezero's interior is largely buried, our results align with hypothesized hydrothermal vents and alteration minerals near central uplifts in similarly sized exposed craters, such as Toro and Auki. Furthermore, our models correspond to alteration patterns observed by the Curiosity in the lower layers of Mount Sharp, which may represent remnants of impact-driven hydrothermal activity. A key finding is that these systems may persist much longer than previously estimated. Our simulations suggest that a Jezero-sized system could remain habitable for thermophiles for approximately 720,000 years, whereas a Gale-sized system could persist for nearly 2 million years. Additionally, simulations under unsaturated crustal conditions reveal that air-dominated near-surface layers can suppress vertical fluid flow, enabling deep subsurface alteration without producing detectable mineral signatures at the surface.

The current volcanic output of Venus is unknown. In the 2030s, the VenSAR (Venus Synthetic Aperture Radar) instrument onboard the European Space Agency's (ESA) EnVision mission will estimate the global volcanic mass flux by looking for new flows with radar imaging at resolutions of 10 or 30 m/pixel, which can be compared with the 1990s-era Magellan data (100–300 m/pixel). Based on eruptions on Earth and Io, we make suggestions for measuring the Venusian global eruptive flux. We do not need to observe small eruptions with Eruption Magnitude (based on mass) <3 because (at least on Earth) they produce <10% of the aggregate erupted mass. Assuming that the size–frequency distribution of Earth lava flows and domes holds on Venus and is augmented to include flows 75% longer as predicted for the Venus surface, we find that all Eruption Magnitude ≥3 eruptions are detectable by VenSAR–VenSAR imaging and >80% by VenSAR–Magellan. However, only 80% of eruptions may produce a detectable change in radar backscatter based on our examination of 24 basaltic terrestrial lava flows from 2014 to 2023 from the ESA Sentinel-1a/b satellites. From observed Earth basaltic flows, thickness will rarely be measured on Venus due to low vertical accuracy. If VenSAR images 20%–40% of the most active volcanoes (as planned), it could detect 79%–92% of the flux if the Eruption Magnitude–frequency distribution is similar to Earth and Io. A few eruptions could then be extrapolated to a global flux, but this is dependent on quantifying the largest eruption, so targeting the right volcanoes is critical.

Lunar and Martian lava tubes will offer stable temperatures and radiation protection, making them potential habitats for extraterrestrial life. The Martian atmosphere, containing gases like H₂, CO, and CH₄, could serve as an energy source for microbes. To address the knowledge gap concerning microbial communities and their survival strategies in Earth's lava tubes, which serve as analogs on Mars, we conducted a study at the Shishan Volcanic Group located in Haikou City, Hainan Province. Through field surveys, microcosm experiments, and multi-omics analyses, we explored the microbial composition and survival mechanisms within these environments. The results revealed that bacterial communities were predominantly composed of Pseudomonadota, Actinomycetota, and Bacillota, while archaeal communities were primarily represented by Thermoproteota and Thermoplasmatota. Bacteria had significantly higher abundance and diversity than archaea, and were positively correlated with low organic matter content. Additionally, the pmoA gene, associated with methane metabolism, was found to be highly abundant, which aligns with the observed high methane oxidation rates. Exposure to 10 ppm CH₄ downregulated methane monooxygenase, hydrogenase, and CO dehydrogenase expression, indicating microbial adaptation to low-concentration trace gases for energy. Genomic analyses show that some bacteria use both the energy-efficient reductive TCA cycle and the high-energy Calvin-Benson cycle to fix carbon dioxide while oxidizing trace gases. This metabolic versatility may provide a competitive advantage over archaea, potentially contributing to the high abundance of bacteria within lava tubes. These findings from Mars-analog lava tubes provide insights into extraterrestrial life survival strategies, advancing our understanding of astrobiology.

Bonestell Crater in Acidalia Planitia and a ∼13 km-diameter crater to the northwest preserve geomorphic and thermophysical evidence of Amazonian-aged glacial activity. In Bonestell, lobate deposits along the northwestern rim and a cirque-like depression along the southeastern rim display steep scarps, lineated textures, and polygonal surface patterns consistent with debris-covered ice and periglacial modification. The cirque depression contains thrust-like ridges and compressional structures resembling terrestrial glacial cirques, interpreted as a remnant of polythermal glaciation, where cold- and warm-based ice likely coexisted. Thermal inertia values across these deposits range from ∼300 to 800 J·M⁻² K⁻¹·s^−1/2, suggesting a downslope transition from poorly consolidated sediment to indurated material. CRISM spectra reveal hydrated minerals and altered silicates consistent with episodic basal melting or volatile-driven alteration. In contrast, the unnamed northwest crater hosts clear examples of rock glaciers. Multiple lobate flows descend from alcoves along the crater walls, exhibiting convex-upward profiles, degraded termini, and compressive ridges that closely resemble terrestrial debris-covered glaciers. HiRISE image data show flow-parallel lineations and banding indicative of internal deformation and sublimation-driven modification. Spectral unmixing of THEMIS ROTO data acquired from multiple viewing geometries fit modeled mixtures of sand and indurated crust with thermal inertia values ∼600 J·M⁻² K⁻¹·s^−1/2, consistent with debris-coated ice. These results demonstrate that mid-latitude ice in the region is preserved in diverse forms, including cirques, rock glaciers, and debris-mantled ice masses. Their co-occurrence indicates that Amazonian glaciation was not singular nor isolated but regionally extensive and capable of producing transient wet-based conditions that locally sustained liquid water and habitable environments.

CM (Mighei-type) carbonaceous chondrites host abundant OH/H₂O-bearing phyllosilicates formed from water-rock reactions in primitive planetesimals. Their infrared (IR) spectral features resemble those of C-type asteroids, making laboratory analyses of CMs essential for interpreting asteroid observations. However, CM chondrites are often breccias composed of lithologies with variable degrees of aqueous alteration, complicating their interpretation. Here we use in situ analytical techniques to characterize spectral-compositional relationships for phyllosilicates in 8 CM lithologies across two meteorite samples. Micro-Fourier Transform Infrared (μ-FTIR) spectra collected from phyllosilicate-rich matrix regions show that band positions of the 3-μm feature and Si-O stretch Reststrahlen band (RB) systematically vary with alteration. Additional data from spatially correlated electron microprobe and μ-FTIR measurements tie spectral variations to specific cation substitutions in serpentines: the 3-μm feature shifts from 2.78 to 2.70 μm with increased Mg/Fe in octahedral sites, and the Si-O stretch RB shifts from 10.8 to 9.8 μm with increased Si/Fe³⁺ in tetrahedral sites. Co-variation of these features across the studied CM lithologies defines two successive alteration stages: (1) the Si-O stretch RB and 3-μm feature shift to longer and shorter wavelengths, respectively, as Mg- and cronstedtite-rich phyllosilicates form from incipient chondrule alteration; (2) Si-O stretch RB shifts to shorter wavelengths as Mg-serpentines replace cronstedtite and Mg-rich chondrules. These patterns align with inferred changes in composition and redox state for altering fluids on the CM parent body. Similar features in the spectra of C-type asteroids may reveal information about conditions of aqueous alteration and constrain models of their evolution.

Thermal tides are global-scale atmospheric waves with periods that are subharmonic to a solar day. Among them, short-period tides (e.g., 6-hr and 4-hr) correspond to higher-order harmonics. Based on temperature profiles from Emirates Mars InfraRed Spectrometer (EMIRS) observations, which provide comprehensive local time coverage, we investigate the 6-hr and 4-hr migrating tides in the Martian atmosphere. These short-period migrating tides exhibit distinct seasonal variations: the 6-hr tide reaches a maximum amplitude of ∼0.7 K around the winter solstice, while the 4-hr tide peaks around the equinoxes with an amplitude of ∼0.5 K. Hough mode decomposition reveals that both the 6-hr and 4-hr migrating tides are dominated by low-order, vertically evanescent modes, consistent with the observed feature that their phases remain nearly constant with altitude. Analysis suggests that the amplitudes of these short-period tides are likely modulated by atmospheric dust and water ice clouds. Furthermore, our results provide observational evidence that the superposition of 6-hr and 4-hr tidal winds around the autumn equinox contributes to the pronounced tropical surface pressure enhancements near 8 a.m. and 8 p.m.

We explored the effect of oscillatory loading on the frictional response of polycrystalline water ice and ice + ammonia to better understand the behavior of tidally modulated strike-slip faults on the icy satellites of the outer solar system, particularly Saturn's moon Enceladus. Ice-on-ice friction experiments were conducted between temperatures of 98 and 248 K at a normal stress of 100 kPa (equivalent to ∼1 km depth in the ice shell). A sinusoidal sliding rate was applied over a range of amplitudes and frequencies at a median velocity of 10 μm/s. We calculated the rate-and-state friction parameters for the amplitude-frequency combinations and found that oscillatory loading alters frictional stability relative to steady-state loading, leading to potentially more unstable slip behavior. We observe a full spectrum of slip behavior, from creep to slow slip to stick-slip. Our system shows a temperature- and velocity-dependent phase lag between the sinusoidal sliding rate and frictional response, which may help explain the phase lag between plume activity and peak stresses on the tiger stripes of Enceladus. Through forward modeling of a sinusoidally-driven slider block, using a rate-and-state dependent friction formulation and experimentally derived parameters, we extrapolate the higher-frequency oscillations in the laboratory experiments to lower frequencies analogous to diurnal tidal stresses on icy satellites. We explore the effect of oscillatory friction on frictional heating rates and fault failure depth with implications for the conditions under which shallow frictional melt generation may be favorable.