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The field of advanced curation is important for existing astromaterials collections, which includes samples returned by space missions, and meteorites and cosmic dust samples that have been recovered from here on Earth. In order to maximize the scientific return of the samples, contamination needs to be minimized at all stages of sample collection, preliminary examination, classification, and curation. Utilizing best practice methods, a detailed acquisition and curation plan was implemented during the UK's first two expeditions to collect Antarctic meteorites from two new blue icefields, Hutchison Icefields and Outer Recovery Icefields. This article documents the design and execution of the procedures used during the project's curation and classification processes. It describes two case studies showing the processes applied to the recovered meteorites, and reviews our experiences and lessons learned for the future. [ABSTRACT FROM AUTHOR]

The Apollo 16 regolith breccia sample suite provides a record of lunar regolith formation from the basin‐forming epoch (~3.9 Ga) through to a time of declining impactor flux (~2 Ga). These rocks have been characterized into three groups: the "ancient," "young," and "soil‐like" regolith breccias on the basis of their petrographic characteristics, and, in the case of the "ancient" and "young" regolith breccias, noble gas inventory. This study investigates the as‐yet unexamined noble gas records of the "soil‐like" regolith breccias to understand more recent regolith evolution processes that occurred at the Apollo 16 landing site. The range of gas concentrations measured for each noble gas in these samples is comparable to those previously reported for the local Apollo 16 soils. The "soil‐like" regolith breccias were found to be more gas rich than the gas poor "young" and "ancient" regolith breccias, consistent with them having formed from comparatively mature soil(s). Our results further confirm the scientific value of lunar regolith breccias and bulk regolith samples as probes of the impact history and the space environment of the lunar surface across a wide range of time. [ABSTRACT FROM AUTHOR]

This issue of Meteoritics & Planetary Science celebrates the science of the Winchcombe meteorite, which fell to Earth on the 28th February 2021 close to the town of Winchcombe, Gloucestershire in the UK. [ABSTRACT FROM AUTHOR]

Mare basalts collected at the Apollo 15 landing site are classified as belonging to either the quartz‐normative suite or the olivine‐normative suite, based on differences in whole‐rock major element chemistry. A wide range of textures are displayed within samples from both suites, which provide insight into eruption processes on the Moon. Here we use crystal size distribution (CSD) analysis and spatial distribution pattern (SDP) analysis of pyroxene, olivine, and plagioclase crystals in eight Apollo 15 mare basalt samples to investigate the crystallization and emplacement of the quartz‐normative and olivine‐normative suites. In general, our results show similarities between the CSDs and SDPs for both mare basalt suites. However, we also report two distinct groups of pyroxene CSD trends that likely represent samples with common cooling histories, originating from comparable depths within respective olivine‐normative and quartz‐normative lava flows. We use our results to determine the relative depths of samples within the lava flows at the Apollo 15 landing site. [ABSTRACT FROM AUTHOR]

Introduction: The Lost Meteorites of Antarctica Project [1,2] retrieved ~120 postulated meteorites from two expeditions to the Outer Recovery (OUT) Icefields and Hutchison (HUT) Icefields, named meteorite dense collection zones, in blue icefields located south of the Shackleton Mountain Range in austral summer 2019 and 2020 [1,2]. A goal of the Lost Meteorites project is to investigate the statistics for different meteorite groups in this previously unsearched part of Antarctica and to understand if there is a sampling bias for stony and iron/stony-iron meteorite types [3]. Thirty-one meteorites collected by the project have been classified to date [4]. Methods: Details of the curation procedures are described in [5]. Magnetic susceptibility and electrical conductivity were measured and are discussed in [6,7]. Chips were prepared into polished blocks and/or thin sections and analysed by SEM at the University of Manchester (UoM). All mineral analyses were by EPMA at the UoM and University of Bristol. Oxygen isotope analysis was conducted at the Open University by laser fluorination of ~2 mg of a larger homogenized sample, reported as per mil deviation from the standard VSMOW [8]. Results: Of the classifications so far, four are achondrites, including a eucrite, an aubrite and two mesosiderites [9], and 27 are chondrites. One of these chondrites is a carbonaceous CM-anomalous chondrite and 26 are ordinary chondrites (OC), including 14 H, 10 L and 2 LL chondrites [4]. All but one of the ordinary chondrites are petrologic types 4, 5 and 6. Outer Recovery Icefields 18016, a 9.5 gram round part-stone with 70% fusion crust (Figs. 1A and 1B), is the most unaltered ordinary chondrite in the collection so far: it has been classified as an L3 based on mineral chemistry. The sample has a magnetic susceptibility of 4.72. A polished section (Fig. 1C) contains abundant welldefined chondrules of different textural types, with pyroxene En89.9±6.2 Fs9.5±6.1 Wo0.7±0.5 (N=14) and olivine Fa21.8±6.2 (N=25). Olivine and pyroxene compositions suggest that the subtype is between 3.5 and 3.8. Discussion: Antarctic studies show that field areas with smaller meteorite populations (<1000) have an overabundance of unusual meteorite types, whereas those where >1000 meteorites were collected converge at ~90% OC [10]. Our classifications so far have a similar OC abundance. Statistics of previous Antarctic collections show 0.83% are eucrites, 0.09% are aubrites and 0.13% are mesosiderites [4]. Our recovery of an aubrite and two mesosiderites from ~120 samples is higher than these values. This may be partly a result of observing a small sample population from only two different collection areas [10]. Samples can be requested from the Meteorite Curator at the Natural History Museum (NHM), London. Acknowledgments: We thank the Leverhulme Trust and BAS for supporting the field campaigns. Funding for curation and classification work was provided by UoM, NHM, and the Royal Society. [ABSTRACT FROM AUTHOR]

Introduction: Samples from the 2500 km diameter lunar farside South Pole Aitken (SPA) basin would be significant as they are expected to hold clues to several key lunar science questions [1-2] including: (i) what is the age of the SPA basin, which will help to anchor the early Earth-Moon impact flux chronology; (ii) what is the nature of igneous rock samples from the lunar farside, and what do these tell us about asymmetries in lunar dif-ferentiation (i.e., urKREEP presence or absence); (iii) how do large impact melt sheets differentiate; (iv) what is the composition and timing of farside mare volcanism and magmatism; and (v) did the SPA basin excavate lunar mantle material [3]? Sample availability: The Chang'e-4 mission analysed in situ the mineral compositions of SPA soils and rocks [4-5], however, to date we do not have samples from the SPA basin itself that have been directly collected by missions. Despite this, we do have the possibility that some Apollo rocks [6] and some samples in the lunar me-teorite collection ([7] and refs. therein) may have originated from within the SPA basin. We focus here on the geochemistry, mineralogy, and chronology records preserved in lunar meteorite Northwest Africa (NWA) 2995, which has been proposed through its pairing with NWA 2996, to be a candidate SPA-derived meteorite [8]. Methods: A 1×0.7 cm thick section of NWA 2995 was polished, carbon coated, and analysed using Scanning Electron Microscopy (SEM) at the University of Manchester to derive whole sample qualitative energy disper-sive spectroscopy X-ray element distribution maps and a backscattered electron (BSE) image. Mineral phases of interest were imaged at high spatial resolution using BSE and cathodoluminescence imaging (CL) at the Universi-ty of Manchester. Some zircon grains were examined by electron backscatter diffraction (EBSD) at the Universi-ty of Portsmouth. The chemical compositions of silicate mineral phases and apatite were analysed at the Institute of Tibetan Plateau Research, Chinese Academy of Sciences, with a JEOL JXA-8230 Electron Probe Micro Ana-lyzer. The sample was also gold coated and analysed at the Institute of Geology and Geophysics, Chinese Acad-emy of Sciences, for U-Pb-isotope dating of zircon and apatite phases using secondary ion mass spectrometry (SIMS) on a Cameca 1280HR instrument. Results and Conclusions: Our section of NWA 2995 is a fragmental breccia with a dark grey matrix, enclos-ing white, brown, and grey clasts (up to 1.5 mm). Mercer et al. [8] report a glass bead in NWA 2996, suggesting that the sample is a regolith breccia representing a fused lunar soil. Clasts consist of a range of impact melt brec-cias with different textures, including clast-bearing and dendritic crystalline types, granulitic breccias, quartz monzogabbros (QMG) and gabbro clasts, and Si-K-rich granophyres. Chi squared test analysis comparing the meteorite's bulk rock composition - including SiO2, Al2O3, MgO, FeO, TiO2, CaO, Th, K, and U abundances [7] - with the Lunar Prospector gamma ray lunar surface composition dataset shows that the meteorite is composition-ally similar to regolith (soil) within the SPA Basin (see also [8]). Zircon and apatite grains within the matrix and QMG clasts yielded U-Pb dates of 4.32-4.33 Ga, which is consistent with the crater count model age range pro-posed for the formation of the SPA basin (from 4.26 to >4.33 Ga [9]). We propose that these U-Pb dates in NWA 2995 correspond to zircon and apatite resetting ages associated with the excavation of various lithologies during the SPA basin forming event, indicating that formation of SPA is at least 4.32 Ga old. This age, which is at the upper end of previous estimates for the age of the basin [9], has important implications for the early bombardment history of the Moon [2]. Our results also indicate that quartz monzogabbro lithologies could be an important component of the lower crust on the farside of the Moon, where they are likely lithological carriers of the small Th-bearing chemistry signature seen from orbit within the SPA basin floor. These findings should be testable in coming years, when the Chang'e-6 mission returns with samples collected from the floor of the SPA basin in ~2023 [10]. [ABSTRACT FROM AUTHOR]

Recovery: At 21:54 (UTC) on the 28th February 2021 a bright fireball was observed over the United Kingdom. The fireball, which lasted ~8 seconds, was widely reported on social media and recorded by 16 stations operated by the six meteor camera networks that collaborate as the UK Fireball Alliance (UKFAll). The main mass (~320 g) of the meteorite was discovered the next morning by the Wilcock family on their driveway in the town of Winchcombe, Gloucestershire. Upon landing, the stone shattered into a pile of dark mm- to cm-sized fragments and powder, most of which was collected using rubber gloves and sealed within polyethylene bags ~12 hours after the fall. In total, >500 g of material was recovered from the local area by members of the public and the UK planetary science community within seven days of the fall, during which time there was no rainfall [1]. The largest intact piece of the Winchcombe meteorite is a 152 g fusion-crusted stone found on nearby farmland on the 6th March. Fireball: The entry velocity of the Winchcombe meteoroid was ~14 kms-1 and the recordings clearly show several fragmentation events. Analysis of the video footage combined with the measurement of short-lived radionuclides suggest that the original body was small (<70 kg). The pre-atmospheric orbit of the Winchcombe meteoroid is similar to those previously reported for the Sutter's Mill (C/CM) [2] and Maribo (CM) chondrites [3]. Petrography: A consortium was quickly established to study the Winchcombe meteorite. Petrographic observations of polished samples indicate that Winchcombe is a CM ("Mighei-like") carbonaceous chondrite [4, 5]. It consists of chondrules [6] and calcium-aluminium-rich inclusions (CAIs) [7] set within a matrix of phyllosilicates, tochilinite-cronstedtite intergrowths (TCIs) [8, 9], carbonates [10], magnetite, and sulphides. Many of the samples show evidence for brecciation and contain multiple distinct lithologies with sharp boundaries. Most lithologies are intermediately to highly aqueously altered (CM2.4 - 2.0), although a rare lithology containing unaltered chondrules and metal has also been identified (~CM2.6). The presence of an unusual Zn-Fe sulphide hints at metasomatism on the parent body [11]. Reflectance spectra of the Winchcombe meteorite show absorption features at ~3 µm and in the mid-infrared (IR) region that are consistent with abundant phyllosilicates [12], while it's fusion crust displays several unique textures related to degassing during atmospheric entry [13]. Composition: The classification of Winchcombe as a CM chondrite is further supported by major and minor element abundances [e.g., 14], and oxygen, titanium, and chromium isotopic compositions [15]. The bulk water content of Winchcombe measured within one month of the fall was ~11 wt.%. Analysis by stepped combustion yielded carbon, nitrogen, and noble gas abundances and isotopic compositions largely consistent with other highly altered CM chondrites [16, 17]. Low voltage SEM characterisation less than a week after the fall of fresh, unpolished fragments located several small (~10's µm) carbon- and nitrogen-bearing regions with "globule-like" morphologies. Carbon K-edge spectra of organic matter in the Winchcombe meteorite show a strong absorption feature at ~285 eV that is assigned to aromatic C=C [18]. Initial analysis by both both liquid (LC-) and gas chromatography-mass spectrometry (GC-MS) revealed extraterrestrial organic components including lipids, fatty acids, and amino acids [19]. Outlook: The Winchcombe meteorite is only the fifth carbonaceous chondrite fall with a known preatmospheric orbit, and due to its rapid recovery is likely the most pristine member of the CM group. The mineralogical, elemental, and organic properties of the Winchcombe meteorite provide a snapshot of conditions in the outer regions of the protoplanetary disk and new insights into the chemical and dynamic evolution of volatiles in the early solar system. The nature and timing of the Winchcombe meteorite fall also makes it complementary to samples of asteroids Ryugu and Bennu collected by the Hayabusa2 and OSIRIS-REx missions, offering an opportunity to develop and rehearse curation and analytical protocols on fresh, carbonaceous materials [20]. [ABSTRACT FROM AUTHOR]

Introduction: The Stac Fada Member is a Mesoproterozoic (1177±5 Ma) single-layer ejecta impactite exposed in NW Scotland [1, 2]. Its deposition history is potentially analogous to that of impact ejecta on Mars [3]. The Stac Fada lithology is composes ca. 20-35% by volume of devitrified and altered vesicular glass. By using micro-Raman spectroscopy, we ascertain whether these altered impact glasses preserve organic carbon compounds and whether these are of astrobiological significant - i.e. can be classified as biosignatures. Indeed, glass buffers peak exposure temperatures and creates an anoxic environment which can preserve and avoid the degradation of organics over geological time [4]. Methods: Samples were collected of the Stac Fada Member at the Stoer and Second Coast outcrops, as well as from the underlying Clachtoll and Bay of Stoer formations. At the University of Manchester, a Leica DM750 optical microscope was used to locate targets in thin sections. For micro-Raman spectroscopy, we used a Horiba Xplora Plus instrument to collect hyperspectral maps with a typical pixel size of 1.5 µm. A 10 mW laser beam at 5 s exposure was used to avoid altering organics. All spectra were background corrected, cosmic ray reduced, and calibrated against ASTM E 1840 polystyrene [5]. Findings: Raman spectroscopy identifies carbon compounds within the Stac Fada altered glasses that has a characteristic three-peak spectrum: a D-peak at 1325 cm-1, a G-peak at 1580 cm-1, and a third peak at ca. 1440 cm-1 which is likely produced by amorphous, diamond-like carbon. The consistent spectra for nearly all organic matter found within Stac Fada suggests a common origin for organics, likely diamond-like carbon formed at high pressure during the impact event. This amorphous diamond-like carbon has later degraded into graphite and other products. Within melt-rich impact breccia samples, disseminated apatite grains ca. 10 µm in size are preferentially found inside altered impact glass. The original glassy melt has been mostly altered to clays (including illite and chlorite) that host diagenetic minerals such as hydroxyapatite and anatase. Raman spectroscopy identifies shorter-chained polyynes with a characteristic spectral peak at ca. 2150 cm-1 in association with a Ti-O rich mineral, likely titanite. Longer chained polyynes, with a characteristic spectral peak at ca. 2090 cm-1, are associated with apatite, characterised by a peak at ca. 963 cm-1 that likely corresponds to hydroxyapatite. Implications: Characterisation of the organic inventory of Stac Fada impact melt-bearing impactites suggests that post-depositional alteration of carbon within impactites may create organic carbon species. Similar to the distribution seen in the Ries crater, Germany [6], impact diamonds are ubiquitous within the melt-rich ejecta deposit. A co-association of apatite and titanite with polyynes, as identified by Raman spectroscopy, suggests that diagenetic alteration of carbon into complex organics may be catalysed by these minerals. Given the likely prevalence of impact-bearing lithologies on the surface of Mars, this has important implications in future searches for martian biosignatures. Surface weathering involving fluids are seen in the Black Beauty family of martian meteorites via the precipitation of Mnoxides [7], and evidence for post-impact hydrothermal alteration is preserved within apatite [8]. Alteration processes seen in the Stac Fada ejecta may be similar to those at the martian surface. [ABSTRACT FROM AUTHOR]

Introduction: The Chang'e-5 landing site is located to the East of Mons Rümker, in the mare unit Em4/P58 [1], one of the youngest mare basalt units on the Moon [2]. A total of 1731 g of soil samples were collected. Initial examination of these samples indicates that the Chang'e-5 basaltic fragments have several distinct textural types, low to intermediate Ti contents, formed ca. 2 billion years ago, were not linked directly to a KREEP reservoir, and originated from a mantle source with low water content [3-9]. These studies have tentatively linked the basaltic material to the Em4 unit, but it remains uncertain whether all of the samples came from a single basaltic unit. This study presents the results of petrological and geochemical investigations of a wide range of clasts, in order to address this uncertainty. Studied samples: We were allocated a 2 g scooped soil sample, CE5C0400, by the Chinese National Space Administration (CNSA) in July 2021. The average particle size is less than 5 microns. Fragments >1 mm picked out of a 1.5 g aliquot of CE5C0400 include 28 basaltic and 7 breccia clasts, 10 agglutinates, and ~200 glass beads >30 um. Results: The textures of the 28 basaltic fragments can be roughly divided into different grain size groups (coarsegrained, ophitic, subophitic, and fine-grained to aphanitic texture). The mineralogy and mineral chemistry of those fragments are very similar, consisting of minerals common in lunar basalts, such as chemically zoned pyroxene, plagioclase, olivine, and ilmenite, with small amounts of potassium-rich glass, potassium-feldspar, Ca-phosphates, and Zr-rich minerals. The pyroxene chemistry (Wo12-43, En3-38, Fs24-85 [coarse], Wo5-44, En0-37, Fs24-94 [ophitic], Wo11-44, En1-50, Fs23-88 [subophitic], Wo5-34, En0-38, Fs12-58 [fine], Wo9-47, En0-39, Fs32-92 [aphanitic]), plagioclase and pyroxene REE abundances, and Pb isotope systematics indicate that there is no distinct difference between different textural types. On the other hand, the chemical composition of some pyroxene grains from breccia and agglutinate clasts appears distinct from the basalt pyroxene compositions, with more Mg-rich and Ca-rich (En>45) compositions, akin to those observed in Apollo low Ti and high Ti lithologies, and some Ca-poor and Mg-rich compositions (Wo<5, En>80) more similar to those found in Mg-suite samples or KREEP basalts [10-12]. The impact glass bead compositions are consistent with having mainly originated from the same Em4 basaltic unit (mean 6 wt.% TiO2 [13]), although ~15% of the studied beads have more exotic compositons, ranging from low- to high-Ti abundances. Discussion: Mineral chemical compositions suggest that the basaltic fragments may represent a single basalt mantle source; we are testing the hypothesis that the textural variations could result from different cooling rates at various locations within a single basaltic flow. Based on the estimated cooling rates (~5 °C/hr for the majority of fragments [14-15]), the sampled fragments could represent only the upper part of the total thickness of the basaltic unit. Available chronology indicates that the sequence could have accumulated within a very short period of time, but determining a precise duration is limited by analytical uncertainties associated with the crystallization ages obtained [3,5]. The breccia and agglutinates lithic clasts, mineral fragments, and glass beads found in the CE5C0400 soil sample appear to be mainly derived from a single underlying basaltic unit, although a few rarer exotic components observed in breccias, agglutinates, and among glass beads may be linked to other types of mare basalts and non-mare lithologies. Acknowledgments: Sample CE5C0400 was provided by CNSA. This study was financially supported by CNSA (Grant Nos. D020204, D020206, and D020203) and the National Key R&D Program of China grant no. 2020YFE0202100. [ABSTRACT FROM AUTHOR]

Introduction: Regolith breccias are surficial soil, rock and mineral fragments that were consolidated into a lithological unit. Consolidation of these materials, into breccias, preserves exposure-burial dependent characteristics arising from space weathering effects. Thus, regolith breccias can serve as a probe of regolith evolution processes in a local area, informing us about parameters such as regolith reprocessing rates at the time of consolidation. Regolith breccia samples collected by the Apollo 16 mission have so-far been grouped into 'ancient', and 'young' regolith breccia groups (consolidated between ~3.8 - 3.4 Ga and ~2.5 - 1.7 Ga, respectively), and a further possible 'soil-like' regolith breccia group (hypothesized to have consolidated <2 Ga) [1-3]. Noble gas measurements support the distinctions between the 'young' and 'ancient' regolith breccia groups but, so far, no noble gas measurements have been reported for the 'soil-like' regolith breccias. Samples and Methods: We visually identified 10 'soil-like' breccia samples from the Apollo 16 sample suite. The samples represent a range of surface exposure (i.e., maturity), based on reported Is/FeO indices [1], and textural classification types [4]. The samples were step heated, and the concentrations and, following cryogenic separation, the isotopic ratios of each noble gas element were analysed using a Thermo Fisher Helix multi-collector mass spectrometer. Heavy (Kr, Xe) and light (He, Ne, Ar) noble gas measurements were made on separate chips of different masses (He, Ne, Ar ~0.1 mg; Kr, Xe ~3 mg), from the same parent sample chip. Discussion: The soil materials comprising the 'young' and 'ancient' regolith breccias are characterised as being immature (i.e., show evidence of lower exposure to lunar surface space weathering processes than more mature samples) [2]. The modern soil materials collected from the Apollo 16 landing site are more mature, and subsequently have accumulated higher noble gas concentration (due to greater abundances of solar wind implanted isotopes) [5]. The aim of this study is address outstanding questions related to how the 'soil-like' regolith breccias fit into the overall regolith breccia suite, and whether the timing of the formation of the 'soil-like' regolith breccias could expand our understanding of an as-yet under represented period of lunar history. Noble gas concentrations. Eight 'soil-like' breccias studied here are more comparable to those noble gas concentrations reported for Apollo 16 soils (i.e., higher), than the 'ancient' and 'young' regolith breccias (which tend to be gas poor) [2,5]. Two further samples allocated appear texturally to be impact melt samples (rather than regolith breccias), this was supported by their gas-poor nature. Cosmic ray exposure ages. Cosmic ray exposure ages were calculated using literature bulk sample chemical compositions [4] and the theoretical cosmogenic nuclide surface production rate model of [6]. We assume that cosmogenic nuclide production occurred on the lunar surface (i.e., at 0 g cm-2) in order to compare our results with data within the literature. However, we note that our Ne isotopic data suggest average burial depths equivalent to within 10 g cm-2 for most samples. Therefore, while the majority of cosmic ray exposure occurred on or near the lunar surface (100× the duration of exposure at depths greater than 10 g cm-2 [7]), a period of exposure at greater depths cannot be ruled out. The 'soil-like' regolith breccias show CRE ages of T3 = 2 - 5 Myr, T21 = 2 - 16 Myr, T38 = 30 - 150 Myr, and T126 = 10 - 35 Myr, and the impact melt breccias have short CRE durations (<100,000 years across all noble gas isotopes). Ar antiquity ages. Using the calibration of [3] and reported sample bulk chemistries [4], we calculated 40Ar(parentless)/36Ar(trapped) antiquity ages for each regolith breccia [3,8] (see [6] for details). Model-dependent antiquity ages have large uncertainties, but they can still establish an estimated timeline between the formation of the youngest and oldest breccias. Two samples show higher antiquity ages of 2.33 and 2.51 Ga, four samples formed between 1.76 to 2.04 Ga, and two samples show ages of 0.86 and 1.33 Ga. These are consistent with ages reported for the Apollo 16 'young' regolith breccias, suggesting that the breccias were consolidated predominantly within the lower Eratosthenian period. Summary: In summary, our new data support the proposition of [1], that these regolith breccias formed from soils that resemble soils found at the Apollo 16 landing site (i.e., they formed from mature, gas rich, regolith). [ABSTRACT FROM AUTHOR]

Contemporary calculations for the flux of extraterrestrial material falling to the Earth's surface (each event referred to as a "fall") rely upon either short-duration fireball monitoring networks or spatially limited ground-based meteorite searches. To date, making accurate fall flux estimates from the much-documented meteorite stranding zones of Antarctica has been prohibited due to complicating glacial ice dynamics and difficulties in pairing together distinct meteorite samples originating from the same fall. Through glaciological analysis and use of meteorite collection data, we demonstrate how to overcome these barriers to making flux estimates. Furthermore, by showing that a clear latitudinal variation in fall frequencies exists and then modeling its mathematical form, we are able to expand our Antarctic result to a global setting. In this way, we hereby provide the most accurate contemporary fall flux estimates for anywhere on Earth. Inverting the methodology provides a valuable tool for planning new meteorite collection missions to unvisited regions of Antarctica. Our modeling also enables a reassessment of the risk to Earth from larger meteoroid impacts--now 12% higher at the equator and 27% lower at the poles than if the flux were globally uniform. [ABSTRACT FROM AUTHOR]