Determining the xenon (Xe) isotope composition of Earth's deep-mantle reservoirs is key to constraining early terrestrial volatile acquisition and subsequent evolution. Here, we employ dynamic mass spectrometry to characterize the Xe isotope composition of the Dos Aguas CO2-rich, cold mineral spring (La Palma, Canary Islands), previously shown to exhibit the highest 3He/4He reported from the Canarian archipelago (10.85 RA). Although the plume mantle-derived Xe contribution is small (<= 0.8%), its signature matches that of the convecting upper mantle (e.g., S129Xe*/S136Xe* approximate to 1; i.e., with comparable 129Xe* and 136Xe* excesses relative to air). This result aligns with the growing evidence that plume mantle- and upper mantle-derived sources are colinear in S129Xe vs. S136Xe and S129Xe*/S136Xe* vs. S130Xe*/136Xe* spaces. For a decade, however, the latter space was considered a powerful means to discriminate between both mantle sources. Here, we use numerical modelling of mantle Xe evolution to answer a simple question: could the distinct evolutions of the highly degassed, convecting upper mantle (primary source of fissiogenic 136Xe*: extant 238U) and the primitive, minimally degassed plume mantle (primary source of 136Xe*: extinct 244Pu) have coincidentally converged towards a unique S129Xe*/S136Xe* approximate to 1. Our model shows that, despite a two orders of magnitude difference in the total extents of degassing, such a coincidence cannot be discarded. An alternative scenario would be that deep, primitive plume mantle sources akin to La Palma may also be dominated by extant 238U fission rather than extinct 244Pu, potentially requiring deep mantle sources to be far more degassed than previously considered.

Operational near-real-time (NRT) monitoring of Earth's surface deformation using interferometric synthetic aperture radar (InSAR) requires processing algorithms that efficiently incorporate new acquisitions without reprocessing historical archives. We present a sequential phase linking approach using compressed single-look-complex (SLC) images capable of producing surface displacement estimates within hours of the time of a new acquisition. Our key algorithmic contribution is a mini-stack reference scheme that maintains phase consistency across processing batches without adjusting or reestimating previous time steps, enabling straightforward operational deployment. We introduce online methods for persistent and distributed scatterer (DS) identification that adapt to temporal changes in surface properties through incremental amplitude statistics updates. The processing chain incorporates multiple complementary metrics for pixel quality that are reliable for small SLC stack sizes, as well as an $L_{1}$ -norm network inversion to limit propagation of unwrapping errors across the time series. We use our algorithm to produce the Observational Products for End-Users from Remote Sensing Analysis (OPERA) Surface Displacement from Sentinel-1 (DISP-S1) product, the first continental-scale surface displacement product over North America. Validation against GPS measurements and InSAR residual analysis demonstrates millimeter-level agreement in velocity estimates in varying environmental conditions. We also demonstrate our algorithm's capabilities with a successful recovery of meter-scale co-eruptive displacement at Kilauea volcano during the 2018 eruption, as well as detection of subtle uplift at Three Sisters volcano, Oregon-a challenging environment for C-band InSAR due to dense vegetation and seasonal snow. We have made all software available as open source libraries, providing a significant advancement to the open scientific community's ability to process large InSAR datasets in a cloud environment.

Abstract Multiple drillings in the Yorke Peninsula, South Australia, recently confirmed the presence of natural hydrogen (H2) in shallow sedimentary units. While radiolysis and Fe‐oxidation in the basement are potential generation mechanisms, their respective contributions remain unconstrained. This study investigates the H2‐generation potential of Fe‐rich Hiltaba Suite granites (∼1.5 Ga) through petrographic analyses of a basement drill core collected near H2 occurrences. Fluid circulation, a prerequisite for both radiolysis and Fe‐oxidation, is evidenced by feldspar sericitization and fluid inclusions. Raman spectroscopy and sample crushing analyses reveal H2 (0.46 mmol/kgrock) and He (0.70–0.88 μmol/kgrock), suggesting that the Hiltaba granites contribute to the gas budget observed in the overlying sedimentary units. He isotopic analyses from bulk granites yield 3He/4He ratios from 0.0003 to 0.0056 Ra, indicating a crustal He origin and a radiolytic H2 generation. A combination of SEM, TEM, EPMA and STXM analyses showed that biotite chloritization did not involve Fe‐oxidation. As biotite is the only primary Fe‐bearing mineral affected by alteration, this rules out any significant contribution of Fe oxidation toH2 generation. Geothermometric calculations indicate that the last fluid circulation event occurred at 300–400°C, implying that the system last opened dynamically at least 370 Ma ago. Consequently, we propose that diffusive migration ofH2 and He from the basement accounts for the gas fluxes in the sedimentary cover. This study represents a first step toward understanding subsurfaceH2 and He generation in the Yorke Peninsula and highlights the Hiltaba Suite's potential to source H2 and He over geological timescales.

Surface displacement measurements from satellite Synthetic Aperture Radar (SAR) have become a critical observational tool for understanding a wide range of natural and anthropogenic processes, including tectonic deformation, landslides, and coastal subsidence. Increasing revisit frequency and data availability now enable systematic monitoring across diverse spatial and temporal scales.We present an application-focused assessment of InSAR displacement monitoring across multiple hazard contexts, drawing on examples from California, Texas, Hawaii, Alaska, and New York in the USA. These case studies demonstrate how InSAR time-series observations can disentangle overlapping deformation signals associated with tectonics, slope instability, volcanic unrest, groundwater-related and coastal subsidence. These examples are framed in the context of practical applications by state and federal agencies, including hazard assessment, infrastructure planning, and coastal risk analysis, highlighting the importance of spatially consistent, operationally usable displacement products. Specifically, we show how variable coastal subsidence impacts present and future sea level estimates for policy decision making in California. We assess the exposure of critical infrastructure, such as petroleum above ground storage tanks, to subsidence and flooding during hurricane events in Houston, Texas. In New York City, we demonstrated natural and anthropogenic vertical land motion impacts on local communities. In volcanic settings, displacement time series are being evaluated by volcano observatories for operational use to detect anomalous trends and characterize evolving surface deformation associated with active and re-awakened systems, including Mauna Loa and Kilauea volcanoes in Hawaii, as well as Mount Edgecumbe volcano in Alaska. Lastly, we demonstrate the use of the displacement time-series to map the spatial extent and slope instability of the Palos Verdes landslide in Los Angeles, California, adding additional observational context for informed decision making by local authorities.This work is performed using OPERA Surface Displacement (DISP) products, which provide spatially consistent, large-scale InSAR displacement fields derived from C-band Sentinel-1 data over North America beginning from 2016. Analyses are supported by advanced and state-of-the-art spatial time-series algorithms designed to support continental-scale processing and a newly developed global tropospheric correction dataset based on the ECMWF High-Resolution Forecast (HRES) numerical weather model. Looking forward, OPERA will incorporate observations from the L-band NASA-ISRO SAR (NISAR) mission, providing continuity and enhanced capability in challenging environments for future displacement monitoring. All OPERA datasets are freely available through NASA archives, and the associated algorithms are developed in open-source repositories, enabling broad scientific reuse, reproducibility, and application.

We introduce a fully automated and scalable method for mapping surface water extents from single-acquisition Sentinel-1 synthetic aperture radar (SAR) imagery. This approach integrates adaptive thresholding of radiometric terrain-corrected SAR backscatter data, fuzzy-logic classification, region growing, dark land estimation, and a bimodality test to minimize false positives in low-backscattering areas and false negatives in high-backscattering areas. By combining these steps, the algorithm achieves classification accuracies exceeding 85% in detecting surface water extents across diverse environmental conditions. Accuracy was first assessed at meter scale using 52 PlanetScope scenes acquired worldwide in September-October 2019; the algorithm achieved 93% overall accuracy, 86% user's accuracy, and 94% producer's accuracy. Global robustness was then evaluated by processing every Sentinel-1 acquisition from 1 to 12 November 2023 and cross-comparing the resulting maps with 6561 temporally matched observational products for end-users from remote sensing analysis (OPERA) dynamic surface water extent from Harmonized Landsat and Sentinel-2 (DSWx-HLS) products. This large-scale test yielded 90% user's and 94% producer's accuracies, confirming reliable performance at continental extent. Additional case studies demonstrate the algorithm's ability to handle surface water extent in sand-dominated deserts, to track seasonal amplitude in Folsom Lake (California), drought-induced loss in Cerro Prieto Reservoir (Mexico), and rapid filling of the Grand Ethiopian Renaissance Dam. These results show that the method scales across local to global domains and maintains high accuracy, providing a practical tool for near-real-time monitoring of floods, droughts, and water-resource management. Because the approach is sensor-agnostic, it can be ported to forthcoming L- and S-band missions such as NASA-ISRO synthetic aperture radar (NISAR), broadening its applicability to future hydrologic observations.

The Atacama Desert in Chile is characterized by its high meteorite density and old meteorite terrestrial ages. In this work, we present new terrestrial ages derived from measurements of the concentration of cosmogenic Cl-36 in the metal fraction of 51 ordinary chondrites collected over a 6.8 km(2) area located in the Catalina Dense Collection Area (Atacama Desert). Cosmic-ray exposure ages were also measured on a subset of the oldest meteorites to confirm that all but one had reached Cl-36 saturation before atmospheric entry. These meteorites have exceptionally old terrestrial ages, with an average of 937 ka (median 701 ka), making this collection the oldest known meteorite collection among hot deserts. This confirms that the Atacama Desert can preserve meteorites for long periods due to the prevailing stable hyper-arid climatic conditions. By combining terrestrial ages with pairing-corrected meteorite density estimates, we estimate the long-term meteorite flux to Earth over the past 2 Myr to be 74 +/- 9 meteorites >20 g per km(2) per Myr. This is consistent with estimates of (i) the modern flux, (ii) the integrated flux over the last similar to 100 kyr determined from Antarctic meteorites, and (iii) the average flux during the last similar to 50 kyr inferred from other hot desert collections. This suggests that the bulk meteorite flux to Earth has remained roughly stable over the past 2 Myr. We also investigate the compositional evolution of the flux by normalizing the H chondrite abundance to the total abundance of ordinary chondrites. Our results show a higher H chondrite abundance between 1200 and 400 ka, followed by a decline to present-day values. This temporal variation is not captured by the current dynamical models for meteoroid transfer to Earth, suggesting that short-term changes in the meteorite flux may be influenced by additional processes operating at a scale not considered by these models.

Land subsidence is a global threat. In Europe, it impacts tens of millions of people by increasing flood risk and damage to the built environment. Land subsidence is the result of a combination of natural and human-induced subsurface processes, and there is considerable potential to mitigate the human-induced drivers through policy and legislation. We show how Europe is approaching the issues of measuring and addressing subsidence at a continental scale. We look ahead to the challenges of climate change and the energy transition in the context of amplifying the impacts of land subsidence, providing lessons learned from the European approach. Millions of people are impacted by land subsidence, which is accelerated by human-induced drivers. Across Europe, research and policy is focused on managing these drivers and mitigating their influence, with data and monitoring infrastructure playing a key role in tackling future challenges.

We investigated geothermal gases from Homa Hills, a carbonatitic complex situated along an adjacent branch of the Kenyan rift system, using neon, argon, krypton, xenon and nitrogen isotopes. Large quantities of gas were sampled in Giggenbach-type bottles (Giggenbach, 1975) and analyzed by dynamic mass spectrometry to resolve isotopic variations at high precision (0.01-0.1 parts per thousand; Seltzer and Bekaert, 2022; Bekaert et al., 2023; 2024). Neon and nitrogen isotope compositions are consistent with parental magmas being derived from the convecting mantle. Xenon isotopic data present ubiquitous enrichments (relative to air) of 129Xe from the decay of extinct 129I (T1/2 = 15.7 Myr) and 131-136Xef from fissions of 238U (T1/2 = 4.468 Myr) and/or 244Pu (T1/2 = 82 Myr). We also find slight excesses of 128Xe (relative to 130Xe and air), which could be due to subsurface isotopic fractionation during e.g., diffusive transport fractionation (DTF) and gravitational settling. However, the 128Xe excesses are not accompanied by correlated Kr isotope excesses and plot off the empirical fractionation line defined from several other locations worldwide (Bekaert et al., 2023). Instead, a detailed isotope deconvolution suggests the occurrence of either chondritic Xe (with mantle 130Xe consisting of up to 22 % of chondritic 130Xe) or recycled Xe from the Archean atmosphere could explain the observed Xe isotope signatures. The latter possibility would have profound implications for models of mantle-surface exchange throughout Earth history. The fission spectra indicate a predominantly 238U origin for fissiogenic Xe, with contribution of 244Pu-derived Xe being negligible within uncertainties, implying extensive mantle degassing during the Hadean and Archean eons. The 129Xe*/136Xe* ratio (where * indicates non-atmospheric excesses of Xe isotopes) of Homa Hills samples correlates with other tracers of mantle/crust contributions such as He, Ar and N isotopes. Variations in 129Xe*/136Xe* among the different gases sampled at Homa Hills is mainly the result of contribution from fissiogenic Xe produced in uranium-rich crustal material. Therefore, this ratio may constitute a robust tracer of mantle-crust interactions. Given available high precision data (Bekaert et al., 2023; 2024; this work) together with mantle-derived rock data, 129Xe*/136Xe* appears homogenous in the convecting mantle, and comparable to values observed at mantle plumes. Such homogeneity is in sharp contrast with light noble gas systematics and may call for whole mantle convection and a core origin for He and Ne..

Heavy vanadium (V) isotope compositions of bulk silicate Earth (BSE) and Mars (BSM) relative to chondrites have been suggested to result from high pressure-high temperature core segregation processes on terrestrial planets. However, an alternative possibility is that these heavy V isotope signatures could reflect inheritance from their differentiated planetary building blocks if, for instance, early formed planetesimals underwent V isotope fractionation during differentiation and/or magma ocean evaporation. To test this hypothesis, we report the first V isotope compositions of 40 achondrites (eucrites and diogenites, angrites, ureilites, and acapulcoiteslodranites) originating from four distinct parent bodies. We find that the bulk silicate portions of (4) Vesta and the Angrite Parent Body (APB) exhibit heavy V isotope signatures relative to chondrites, comparable to (or greater than) BSM, but lighter than BSE. On the contrary, the Ureilite Parent Body (UPB) and the Acapulcoite/ Lodranite Parent Body (ALPB) are indistinguishable from the chondritic value. To investigate the origin of these V isotope variations, we combine V isotope data with the systematics of other elements. First, we show that differentiated planetary bodies do not exhibit clear V-Sr isotope covariations similar to those recently observed for calcium-aluminum-rich inclusions (CAIs). Only the heavy V isotope signature of (4) Vesta could have potentially resulted from accretionary and/or magma ocean volatilization processes (reflecting similar to 0.6 % V and Sr loss). To account for the heavy V but chondritic Sr isotope compositions of the APB, BSM, and Moon, we suggest either (i) extremely large isotope fractionation of V during core formation, or (ii) significantly higher metal-silicate partition coefficients (i.e., more siderophile V) than expected based on experimental data and planetary body conditions. Alternatively, conditions of nebular evaporation recorded in CAIs may not apply to planetary evolution, or the volatilities of V and Sr may differ significantly under early planetary conditions. Similarly, we observe no strong correlation between V and evaporation-sensitive elements like K, likely due to K's much higher volatility compared to V. Potential correlations between V and elements such as Mg (R-2 = 0.98), Si (R-2 = 0.81), and Fe (R-2 = 0.46) suggest that these elements - in particular Mg - may exhibit volatilities closer to V than to K or Sr during planetary evaporation. Explaining bulk delta V-51 variations through vapor-melt fractionation - rather than V partitioning into the core - would alleviate potential conflicts between our data and previous modeling based on available experimental results regarding V metal-silicate partitioning. In any case, the lack of a V isotope anomaly for the UPB and ALPB indicates that the processes responsible for the heavy V isotope compositions of (4) Vesta, the APB, and the terrestrial planets did not occur on these two bodies. This result is consistent with a lack of global magma ocean formation on these parent bodies, as independently suggested by the preservation of mass independent oxygen isotope heterogeneities throughout the mantles of both parent bodies.

In subduction zones, thermal springs release deeply-sourced volatiles from Earth's mantle, crust, and/or subducted slab-derived material. The origin and apparent ages of these volatiles are important for understanding the deep volatile cycle, which in turn affects the distribution of microbial life in the subsurface. Here, we report carbon (C-13, C-14), noble gas (He, Ne, Ar, Kr and Xe), and clumped nitrogen isotope data in gas and water samples from thermal springs within the Central Volcanic Zone (CVZ) of the Andean Convergent Margin (ACM). He isotopes show that CVZ gases are predominantly sourced from the crust (similar to 77 %), with smaller mantle contributions (similar to 23 %), consistent with previous studies from the CVZ. Thermal spring samples with non-atmospheric He-Ne characteristics have low C-14 activities, and are deeply derived (i.e., from the mantle and crust) and old (>22,000 years). To gain additional constraints on volatile sources, a gas sample from Pirquitas Argentina was analyzed using a new high-precision technique to reveal significant geogenic anomalies in argon (Ar-40/Ar-36 = 492), fissiogenic xenon (88 % crustal), and helium (84 % crustal) isotopes. Clumped N-2 isotopologue results also indicate that the N-2-rich Pirquitas sample is dominated by crustal and magmatic N-2, which was unambiguously released at high temperatures (indicated by Delta(30) of similar to 0 parts per thousand). When taken together, all carbon, noble gas and clumped N-2 isotope data from CVZ thermal springs point toward a predominantly crustal source of volatile elements, which is consistent with the thick crust beneath the arc. We conclude that thermal springs with noble gas isotopic evidence for minimal air contributions are old, suggesting that any microbial communities entrained in them are also supported by deeply-derived and old organic carbon.

Sources of nitrogen (N) in the plume mantle source remains hotly debated between a primordial origin (i.e., acquired during Earth's formation) and a recycled origin associated with subduction of surficial material. Although N isotope data for plume-derived magmas are limited, the available data show clear differences in N isotope compositions between plume (delta N-15 > -2 parts per thousand) and the depleted mid-ocean-ridge basalt mantle sources (i.e., DMM; delta N-15 = -5 +/- 2 parts per thousand). Here we present N-isotope and noble gas isotope data from two suites of well-characterized plume-influenced submarine basaltic glasses with high He-3/He-4: 1) the Rochambeau Bank in the northeastern Lau backarc basin (up to similar to 23 RA, where RA refers to the atmospheric He-3/He-4 ratio), and 2) the Reykjanes Ridge (up to similar to 18 R-A) south of Iceland. These sample suites are associated with different tectonic settings: the Tonga subducting slab interacts with the Samoan plume beneath the Lau backarc basin, whereas the Mid-Atlantic Ridge interacts with the Icelandic plume at the Reykjanes Ridge. The contrasting tectonic settings provide a unique opportunity to decipher both the origin of N in plume mantle sources and the interaction of the plume mantle with other mantle components, including recycled material from subducting slabs and the DMM. Our results show that Rochambeau Bank (delta N-15 from +1.3 parts per thousand to +2.8 parts per thousand) and Reykjanes Ridge samples (delta N-15 from -2.3 parts per thousand to +0.1 parts per thousand) are both characterized by delta N-15 values that are enriched relative to the DMM. Rochambeau Bank data are consistent with ternary mixing between the DMM (delta N-15 = -5 +/- 2 parts per thousand; N-2/He-3 = 3.7 +/- 1.2 x 10(6); N-2/Ar-40* = 138 +/- 65), a subduction component from the adjacent Tonga slab with recycled N (delta N-15 = similar to+3 parts per thousand; N-2/He-3 = similar to 10(9); N-2/Ar-40* = similar to 5 x 10(6)), and a third component with delta N-15 = similar to 0 %, N-2/He-3 = similar to 2 x 10(5) and N-2/Ar-40* = similar to 40, which we attribute to the Samoan plume component enriched in primordial N. In contrast, Reykjanes Ridge data, combined with Iceland data, are consistent with ternary mixing among the DMM, plume components with recycled N (delta N-15 from 0 parts per thousand to +6 parts per thousand; N-2/He-3 = similar to 10(9); N-2/Ar-40* = similar to 5 x 10(6)) and primordial N (delta N-15 from -2 parts per thousand to +2 %; N-2/He-3 = similar to 2 x 10(5); N-2/Ar-40* = similar to 40) endmembers in deep Icelandic mantle plumes. This is consistent with the presence of both recycled and primordial N being intrinsic to the Icelandic mantle plume. By integrating N data from other global plume-influenced samples (i.e., Society, Hawaii, and Central Indian Ridge), we show that the global dataset is consistent with ternary mixing among the DMM, and plume components entrained with both recycled N and primordial N. Nitrogen in deep plume sources is therefore likely hybrid in composition, containing both recycled N from subducting slab and primordial N retained from Earth's early stages of formation. The heavier delta N-15 of an apparent primordial N component within plume mantle sources (-2 parts per thousand to +2 parts per thousand) relative to that of the convecting MORB mantle (similar to-5 parts per thousand) potentially requires an addition of N-15-rich carbonaceous material from the outer solar system to the early accreting Earth.

Coastal vertical land motion (VLM), including uplift and subsidence, can greatly alter relative sea level projections and flood mitigations plans. Yet, current projection frameworks, such as the IPCC Sixth Assessment Report, often underestimate VLM by relying on regional linear estimates. Using high-resolution (90-meter) satellite data from 2015 to 2023, we provide local VLM estimates for California and assess their contribution to sea level rise both now and in future. Our findings reveal that regional estimates substantially understate sea level rise in parts of San Francisco and Los Angeles, projecting more than double the expected rise by 2050. Additionally, temporally variable (nonlinear) VLM, driven by factors such as hydrocarbon and groundwater extraction, can increase uncertainties in 2050 projections by up to 0.4 meters in certain areas of Los Angeles and San Diego. This study highlights the critical need to include local VLM and its uncertainties in sea level rise assessments to improve coastal management and ensure effective adaptation efforts.

Samples returned from the carbonaceous asteroid (162173) Ryugu show mineralogical, chemical, and isotopic similarities with Ivuna-type (CI) carbonaceous chondrites, which likely contributed to Earth's volatile inventory. To better understand the complex Ne-Ar-N signature of CI-type material, we analysed a single, mg-sized Ryugu particle by multi-step (n n = 85) heating. Noble gases (Ne, Ar) are a mixture between implanted Solar Wind (SW), presolar component(s), and the carbonaceous phase Q, with negligible cosmogenic contributions. The 6 15 N variations observed during progressive heating reflect the presence of various N-bearing phases. The large number of heating steps provide key insights into the effect of thermal processing on the N abundance and isotopic ratio, and indicate that low temperatures can result in extensive N loss from CI-type material, without significantly affecting the bulk N isotopic composition. Nitrogen isotopes, therefore, remain a reliable and powerful tool for tracing volatile sources in the Solar System.

The NASA-ISRO Synthetic Aperture Radar (NISAR) Mission experienced some technical issues in observatory level testing that required mitigations to be carried out on the reflector system, preventing a launch in 2024 as previously planned. The reflector has been reconditioned to address these issues, and NISAR is now on target for launch in early 2025. After launch, the spacecraft is planned to undergo commissioning for period of 90 days, after which science operations will begin. NISAR has two radar instruments - an L-band (24 cm wavelength) radar provided by NASA, and an S-band (9.4 cm wavelength) radar provided by ISRO - each of which can be operated individually or simultaneously. Each radar has a swath width of greater than 240 km for all modes at a variety of resolutions and polarimetric states. Due to precise orbit control and pointing, each radar also will produce repeat-pass interferometric measurements over all science targets. During the science phase, NISAR will collect about 35 Terabits of L-band radar image data each day, observing all land and ice-covered surfaces of Earth on the ascending and descending portions of each orbit every 12 days, and collecting about 5 Terabits of S-band radar image data each day over India and surrounding areas, Antarctica, and distributed global scientific areas of interest. Nearly all S- band acquisitions are collected simultaneously with L-band acquisitions, creating a unique globally distributed time- series data set. The commissioning plan calls for early engineering mode acquisitions around one month after launch, some of which may be usable to form images, followed by a period of orbit adjustment and system timing and pointing calibration. To prepare for science operations, the NISAR project has worked with the science team to develop a list of observational areas where early data can be acquired to demonstrate the preliminary quality of the data and to illustrate the science themes NISAR is addressing: solid Earth sciences, ecosystems sciences including global soil moisture, and cryosphere sciences, as well as many applications. In addition, cloud-based tools for image processing and diagnostic analysis, usable by the project and science team members alike, will be available to examine these early data sets.

Accurate monitoring of ground deformation is important for understanding the processes that lead to natural disasters, and the health and safety of society. The discovery of a fading signal has put the accuracy of methods that utilise multilooking and short-temporal interferograms into question. A symptom of this signal is that multilooked interferograms may exhibit a non-zero phase loop closure. We compare the phase loop closure in C-band and L-band InSAR data over different land cover types for an area centered on Milan, Italy. Our findings suggest that changes in volume scattering are the leading cause of phase loop misclosure and the fading signal in this area. We also investigate the effects of multilooking on the magnitude of phase loop misclosure with the goal of developing a model of the fading signal for both C-band and L-band InSAR.