Micrometeorites from the Transantarctic Mountains

We report the discovery of large accumulations of micrometeorites on the Myr-old, glacially eroded granitic summits of several isolated nunataks in the Victoria Land Transantarctic Mountains. The number (>3,500) of large (>400 μm and up to 2 mm in size) melted and unmelted particles is orders of magnitudes greater than other Antarctic collections. Flux estimates, bedrock exposure ages and the presence of ≈0.8-Myr-old microtektites suggest that extraterrestrial dust collection occurred over the last 1 Myr, taking up to 500 kyr to accumulate based on 2 investigated find sites. The size distribution and frequency by type of cosmic spherules in the >200-μm size fraction collected at Frontier Mountain (investigated in detail in this report) are similar to those of the most representative known micrometeorite populations (e.g., South Pole Water Well). This and the identification of unusual types in terms of composition (i.e., chondritic micrometeorites and spherulitic aggregates similar to the ≈480-kyr-old ones recently found in Antarctic ice cores) and size suggest that the Transantarctic Mountain micrometeorites constitute a unique and essentially unbiased collection that greatly extends the micrometeorite inventory and provides material for studies on micrometeorite fluxes over the recent (≈1 Myr) geological past.     

Early inner solar system origin for anomalous sulfur isotopes in differentiated protoplanets

Achondrite meteorites have anomalous enrichments in ³³S, relative to chondrites, which have been attributed to photochemistry in the solar nebula. However, the putative photochemical reactions remain elusive, and predicted accompanying ³³S depletions have not previously been found, which could indicate an erroneous assumption regarding the origins of the ³³S anomalies, or of the bulk solar system S-isotope composition. Here, we report well-resolved anomalous ³³S depletions in IIIF iron meteorites (<−0.02 per mil), and ³³S enrichments in other magmatic iron meteorite groups. The ³³S depletions support the idea that differentiated planetesimals inherited sulfur that was photochemically derived from gases in the early inner solar system (<∼2 AU), and that bulk inner solar system S-isotope composition was chondritic (consistent with IAB iron meteorites, Earth, Moon, and Mars). The range of mass-independent sulfur isotope compositions may reflect spatial or temporal changes influenced by photochemical processes. A tentative correlation between S isotopes and Hf-W core segregation ages suggests that the two systems may be influenced by common factors, such as nebular location and volatile content.Of all of the extraterrestrial materials found on Earth, iron meteorites have always been the most conspicuous. So-called “magmatic” iron meteorites are likely to be samples from the cores of magmatically differentiated protoplanetary parent bodies (1), whereas “nonmagmatic” iron meteorites are commonly suggested to sample solidified melt pockets that formed via impacts onto nondifferentiated (chondritic) parent bodies (2). Individual members from an iron meteorite group are assumed to derive from a common parent body, based on shared chemical and isotopic characteristics (1–4). Chemical and isotopic differences among the different iron groups provide convincing evidence that different individual parent body planetesimals incorporated genetically distinct precursor materials (1–4).Recent observations that several achondrite meteorite groups possess small, mass-independent ³³S enrichments relative to chondrites (5) have led to the conclusion that sulfur isotopes were heterogeneously distributed among the materials that accreted to form early solar system planetesimals. This observation, coupled with the ancient ¹⁸²Hf-¹⁸²W ages (within 1–3 My of solar system formation) of magmatic irons (6–8), provides impetus to search for systematic variations in mass-independent sulfur isotope compositions among the iron groups.     

Massive isotopic effect in vacuum UV photodissociation of N2 and implications for meteorite data

Nitrogen isotopic distributions in the solar system extend across an enormous range, from −400‰, in the solar wind and Jovian atmosphere, to about 5,000‰ in organic matter in carbonaceous chondrites. Distributions such as these require complex processing of nitrogen reservoirs and extraordinary isotope effects. While theoretical models invoke ion-neutral exchange reactions outside the protoplanetary disk and photochemical self-shielding on the disk surface to explain the variations, there are no experiments to substantiate these models. Experimental results of N₂ photolysis at vacuum UV wavelengths in the presence of hydrogen are presented here, which show a wide range of enriched δ¹⁵N values from 648‰ to 13,412‰ in product NH₃, depending upon photodissociation wavelength. The measured enrichment range in photodissociation of N₂, plausibly explains the range of δ¹⁵N in extraterrestrial materials. This study suggests the importance of photochemical processing of the nitrogen reservoirs within the solar nebula.Nitrogen isotopic analyses of meteorites, terrestrial planets, atmospheres of giant planets and their moons, solar wind, comets, and interplanetary dust particles (1) may advance understanding of volatile chemistry and prebiotic processes in the early solar system.     

From the Cover: Magnetic evidence for a partially differentiated carbonaceous chondrite parent body

The textures of chondritic meteorites demonstrate that they are not the products of planetary melting processes. This has long been interpreted as evidence that chondrite parent bodies never experienced large-scale melting. As a result, the paleomagnetism of the CV carbonaceous chondrite Allende, most of which was acquired after accretion of the parent body, has been a long-standing mystery. The possibility of a core dynamo like that known for achondrite parent bodies has been discounted because chondrite parent bodies are assumed to be undifferentiated. Resolution of this conundrum requires a determination of the age and timescale over which Allende acquired its magnetization. Here, we report that Allende’s magnetization was acquired over several million years (Ma) during metasomatism on the parent planetesimal in a >  ∼ 20 μT field up to approximately 9—10 Ma after solar system formation. This field was present too recently and directionally stable for too long to have been generated by the protoplanetary disk or young Sun. The field intensity is in the range expected for planetesimal core dynamos, suggesting that CV chondrites are derived from the outer, unmelted layer of a partially differentiated body with a convecting metallic core.     

Condensation time of the solar nebula from extinct I in primitive meteorites

Mineral separates from five carbonaceous chondrites were dated by extinct 16 million year ¹²⁹I, in an attempt to establish the condensation time of the solar nebula. Two Fe₃O₄ or Fe₃O₄-FeS samples from the Murchison and Orgueil meteorites are older than any other material dated thus far, and apparently formed within 2 × 10⁵ years of each other. The great age, close isochronism, and primitive nature of the samples suggest that the event recorded was the condensation stage of the solar nebula. It provides a suitable zero point for the chronology of the early solar system. The ¹²⁹I/¹²⁷I ratio during condensation of the nebula was (1.46 ± 0.04) × 10^-4. The recrystallized C4 chondrite Karoonda began to retain ¹²⁹Xe 1.8 ± 0.5 million years after the above event. This short cooling time implies rapid aceretion (≤1 million years) and a shallow origin (≤10 km) below the surface of its parent body.     

The origin of volatile elements in the Earth–Moon system

The origin of volatile species such as water in the Earth–Moon system is a subject of intense debate but is obfuscated by the potential for volatile loss during the Giant Impact that resulted in the formation of these bodies. One way to address these topics and place constraints on the temporal evolution of volatile components in planetary bodies is by using the observed decay of ⁸⁷Rb to ⁸⁷Sr because Rb is a moderately volatile element, whereas Sr is much more refractory. Here, we show that lunar highland rocks that crystallized ∼4.35 billion years ago exhibit very limited ingrowth of ⁸⁷Sr, indicating that prior to the Moon-forming impact, the impactor commonly referred to as “Theia” and the proto-Earth both must have already been strongly depleted in volatile elements relative to primitive meteorites. These results imply that 1) the volatile element depletion of the Moon did not arise from the Giant Impact, 2) volatile element distributions on the Moon and Earth were principally inherited from their precursors, 3) both Theia and the proto-Earth probably formed in the inner solar system, and 4) the Giant Impact occurred relatively late in solar system history.

Understanding the formation of the Moon has long been a topic of intense interest, although hard constraints on this event only developed after the Apollo program returned lunar samples to Earth. Based on the thousands of lunar rocks that have been studied to date, arguably one of the most stringent of these constraints is that the Moon is strongly depleted in volatile elements relative to the solar photosphere, primitive meteorites, and Earth. Recognition of such a depletion of volatile elements, combined with the orbital mechanics of the Moon and geochemical evidence that it differentiated from a mostly molten state, led to the now widely accepted “Giant Impact” hypothesis, in which the Moon accreted from a volatile element–depleted debris disk produced by an impact between a Mars-sized body (Theia) and the proto-Earth (1). Yet, the formation of the Moon through such an impact scenario raises questions about the composition of the proto-Earth and Theia and their respective contributions to the makeup and subsequent evolution of the Earth–Moon system. Of particular interest is how and when the Moon and Earth obtained their present allotments of volatile components, including, and most importantly, water. Did the Moon and Earth form with their current allotments of volatile elements, or were these elements lost during the Giant Impact and reintroduced to Earth by later accretion of volatile element–laden materials? Here, we address this issue using the Rb–Sr isotopic systematics of lunar samples to provide time constraints on the history and distribution of volatile elements in the Earth–Moon system.     

Synthesis of refractory organic matter in the ionized gas phase of the solar nebula

In the nascent solar system, primitive organic matter was a major contributor of volatile elements to planetary bodies, and could have played a key role in the development of the biosphere. However, the origin of primitive organics is poorly understood. Most scenarios advocate cold synthesis in the interstellar medium or in the outer solar system. Here, we report the synthesis of solid organics under ionizing conditions in a plasma setup from gas mixtures (H₂(O)−CO−N₂−noble gases) reminiscent of the protosolar nebula composition. Ionization of the gas phase was achieved at temperatures up to 1,000 K. Synthesized solid compounds share chemical and structural features with chondritic organics, and noble gases trapped during the experiments reproduce the elemental and isotopic fractionations observed in primitive organics. These results strongly suggest that both the formation of chondritic refractory organics and the trapping of noble gases took place simultaneously in the ionized areas of the protoplanetary disk, via photon- and/or electron-driven reactions and processing. Thus, synthesis of primitive organics might not have required a cold environment and could have occurred anywhere the disk is ionized, including in its warm regions. This scenario also supports N₂ photodissociation as the cause of the large nitrogen isotopic range in the solar system.The solar system formed from the gravitational collapse of a dense core within a molecular cloud that led to the ignition of a central star surrounded by a protoplanetary disk. Protoplanetary disks are evolving and dynamic systems, in which complex chemistry results in the formation and aggregation of solids. Among them, organic molecules are of great astrobiological interest because they may represent the first building blocks of prebiotic molecules. Moreover, they are the main carriers of volatile elements (i.e., H, C, N, and noble gases) that formed the atmospheres of the inner planets. Organic matter is ubiquitous in primitive solar system bodies [e.g., chondrites, especially the carbonaceous ones, interplanetary dust particles (IDPs), and cometary dust—Comet 81P/Wild 2 and ultracarbonaceous Antarctic micrometeorites (UCAMMs) (1–3)]. Most meteoritic organics (up to 99%) are in the form of a refractory and insoluble macromolecular solid, commonly referred to as insoluble organic matter (IOM) (e.g., ref. 4). Notably, IOM displays bulk D and ¹⁵N isotope excesses relative to solar composition, which can reach extreme values at a microscopic scale (5, 6). These compositional and isotopic characteristics bear a unique record of the processes and environmental conditions of IOM synthesis, but the message is still cryptic.IOM is also the main carrier of the heavy noble gases (Ar, Kr, and Xe) as well as of a small fraction of He and Ne trapped in chondrites. The exact host phase of these elements—nicknamed Phase Q (7)—is not well characterized and appears to be a part of, or at least chemically associated with, refractory organic compounds (7–9). This Q component is ubiquitous in primitive chondrites (10, 11), in IDPs, and in Antarctic micrometeorites (12). Thus, Q gases may represent the most important noble gas reservoir outside the Sun at the time of accretion in the protosolar solar nebula (PSN). Q gases are elementally and isotopically fractionated relative to the solar composition [as inferred by the analysis of solar wind composition (13–16)], in favor of heavy elements and isotopes, by about 1%/atomic mass unit (amu) for Xe isotopes (11). So far, only plasma experiments involving noble gas ionization were able to fractionate noble gases elementally and isotopically to extents comparable to those of Q (17–22). Both Q gases and IOM are intimately related and ubiquitous in primitive solar system bodies, likely pointing to a common and preaccretion origin.Several processes for IOM synthesis have been proposed and/or studied experimentally, reflecting the variety of astrophysical regions where organosynthesis may occur. Most of them involve cold scenarios (e.g., below 40 K) via UV-induced grain surface polymerization of organic molecules in the icy mantles of dust grains, either in the interstellar medium (ISM) or in the outer solar nebula (e.g., refs. 23 and 24). It has been also proposed that organosynthesis could have occurred onto the parent body of chondrites via polymerization of interstellar formaldehyde (25, 26), or via Fischer−Tropsch-like reactions onto metal grains at warm temperature (e.g., 300 K or above) (27, 28). Laboratory works reproduced partially the compositional features of chondritic/cometary refractory organics, but generally failed to reproduce the large D and ¹⁵N excesses (relative to the PSN composition) observed in the inner planets, meteorites, and comets. These experiments did not address either the elemental or isotopic fractionations of noble gases.In this work, we present a plasma experiment designed to produce refractory solid organics from mixtures of C- and N-bearing gases representative of the composition of the solar nebula (i.e., CO, N₂ with addition of noble gases). This is the first integrative study, to our knowledge, that investigates organosynthesis and noble gas issues simultaneously.     

Comparison of lunar with terrestrial and meteoritic rocks

This note examines critically recent attempts to identify or closely correlate lunar surface samples—on the basis of alpha-scattering analysis—with terrestrial igneous rocks (basalts) or with eucrite meteorites. Basalts show considerable variety; but all have chemical characteristics inherited from terrestrial mantle rock melted under a limited range of terrestrial pressure-temperature conditions. What is characteristic is not so much the content of any particular element or oxide—e.g., SiO₂ 47-52 per cent—but rather a complete chemical pattern in which such ratios as Fe/Mg and Ca/(Na + K) show consistent relationships to Si content. These are the chemical criteria that might be useful in comparing terrestrial basalt with extraterrestrial rocks. Basalts also have distinctive mineralogical and textural characteristics; and if a lunar or meteoritic rock is to be identified as basalt it must possess these, too.

Turkevich's analysis of alpha-scattering data for lunar samples (Surveyor V) show significant departure from basaltic composition: Very high (Ca + K)/Na associated with distinctly high Fe/Mg. In basalts relatively high (Ca + K)/Na—in no case approaching the reported lunar values—tends to be associated with Fe/Mg values lower than average. The same “lunar” pattern of high (Ca + K)/Na and Fe/Mg appears in recorded analyses of eucrite meteorites. In the lunar samples, Ti is notably higher than in basalts, and even more so than in eucrites. If eucrites are of lunar origin their Ti values are, so far, a real anomaly.

     

Pristine extraterrestrial material with unprecedented nitrogen isotopic variation

Pristine meteoritic materials carry light element isotopic fractionations that constrain physiochemical conditions during solar system formation. Here we report the discovery of a unique xenolith in the metal-rich chondrite Isheyevo. Its fine-grained, highly pristine mineralogy has similarity with interplanetary dust particles (IDPs), but the volume of the xenolith is more than 30,000 times that of a typical IDP. Furthermore, an extreme continuum of N isotopic variation is present in this xenolith: from very light N isotopic composition (δ¹⁵N_AIR = −310 ± 20‰), similar to that inferred for the solar nebula, to the heaviest ratios measured in any solar system material (δ¹⁵N_AIR = 4,900 ± 300‰). At the same time, its hydrogen and carbon isotopic compositions exhibit very little variation. This object poses serious challenges for existing models for the origin of light element isotopic anomalies.     

Exploring the Relationship Between Serum and Urinary Free Light Chain Levels During the Different Phases of Renal Damage in Multiple Myeloma Patients

The objective was to explore the relationship between the levels of serum and urinary free light chains (FLCs) during the progression of renal damage in multiple myeloma (MM) patients. We examined 91 cases of MM patients, detected levels of serum FLCs (sFLCs), urinary FLCs (uFLCs), and serum creatinine at the same time, and then compared sFLC and uFLC levels during normal and abnormal serum creatinine phases. Among the 91 MM patients, 22 patients had abnormal serum creatinine levels (no uremia), and 69 patients had normal serum creatinine levels. The levels of sFLCs and uFLCs in patients with abnormal serum creatinine were beyond normal, namely both serum and urine positive (serum+ and urine+), and the average concentrations of κFLCs and λFLCs were 516.76 and 604.67 mg/L, respectively. Of the 69 patients with normal creatinine levels, there were 39 and 30 cases of κ-type and λ-type MM, respectively. Of the κ-type patients, 11 cases were serum positive and urine negative (serum+ and urine−) with an average concentration of 55.47 mg/L, and 28 cases were serum positive and urine positive (serum+ and urine+) with an average concentration of 513.09 mg/L. Of the λ-type patients, 16 cases were serum positive and urine negative (serum+ and urine−) with an average concentration of 78.44 mg/L, and 14 cases were serum positive and urine positive (serum+ and urine+) with an average concentration of 518.08 mg/L. The levels of uFLCs did not parallel those of sFLCs. In addition to sFLC levels, renal function affected uFLC concentrations. As MM progressed, the concentration of sFLCs increased in a step-by-step manner, and the uFLCs changed from negative to positive to negative again. Therefore, the whole progression included three phases: sserum+ and urine−, serum+ and urine+, and then serum+ and urine−.     

Potassium isotope composition of Mars reveals a mechanism of planetary volatile retention

The abundances of water and highly to moderately volatile elements in planets are considered critical to mantle convection, surface evolution processes, and habitability. From the first flyby space probes to the more recent “Perseverance” and “Tianwen-1” missions, “follow the water,” and, more broadly, “volatiles,” has been one of the key themes of martian exploration. Ratios of volatiles relative to refractory elements (e.g., K/Th, Rb/Sr) are consistent with a higher volatile content for Mars than for Earth, despite the contrasting present-day surface conditions of those bodies. This study presents K isotope data from a spectrum of martian lithologies as an isotopic tracer for comparing the inventories of highly and moderately volatile elements and compounds of planetary bodies. Here, we show that meteorites from Mars have systematically heavier K isotopic compositions than the bulk silicate Earth, implying a greater loss of K from Mars than from Earth. The average “bulk silicate” δ⁴¹K values of Earth, Moon, Mars, and the asteroid 4-Vesta correlate with surface gravity, the Mn/Na “volatility” ratio, and most notably, bulk planet H₂O abundance. These relationships indicate that planetary volatile abundances result from variable volatile loss during accretionary growth in which larger mass bodies preferentially retain volatile elements over lower mass objects. There is likely a threshold on the size requirements of rocky (exo)planets to retain enough H₂O to enable habitability and plate tectonics, with mass exceeding that of Mars.

Examining the presence, distribution, and abundance of volatile elements and compounds, including water, on Mars has been a central theme of space exploration for the past 50 y. The majority of all past, ongoing, and future Mars missions involve the direct or indirect study of volatile element inventories, including the recent “Perseverance” and “Tianwen-1” missions (1, 2). The direct study of volatiles in martian meteorites, along with remote sensing efforts, have significantly broadened understanding of the volatile inventory of Mars and spurred the development of competing bulk chemistry models for Mars. These models can broadly be divided into three groups: 1) those based on cosmochemical implications of elemental ratios (3–5), 2) those attempting to reproduce the martian O isotope composition by mixing different proportions of chondritic materials (6, 7) and equating these to volatile abundances, and 3) those combining spacecraft data and meteorite chemistry to estimate the composition of bulk silicate Mars (8). These models all adopted the ratios of volatile element K to the refractory elements U and Th as a proxy of volatile depletion because these elements are all highly incompatible and lithophile during igneous processes, that is, such ratios are not strongly affected by partial melting followed by melt fractionation that leads to the formation of basaltic rocks and their derivatives that constitute the present-day martian crust. Furthermore, the concentrations of K, Th, and U of this martian crust can be measured remotely from orbit using gamma-ray spectrometry (GRS). All previous models for the composition of bulk silicate Mars, as well as GRS data of exposed martian surface materials, have shown that Mars has elevated K/Th as well as higher contents of a greater suite of moderately volatile elements relative to Earth (Fig. 1), together implying a volatile-rich early Mars (8–10). A caveat with these models is the inherent difficulty in determining the K/Th of bulk silicate Mars from surface data as well as the marked inconsistency between meteorite analyses and GRS data of martian surface regions (9).Open in a separate windowFig. 1.Potassium to thorium ratios versus the corresponding K concentrations of martian meteorites (basaltic, olivine-phyric, and lherzolitic shergottites and other categories), the martian surface detected by the Mars Odyssey Gamma Ray Spectrometer, and terrestrial mid-ocean ridge basalts (MORB) and ocean island basalts (OIB). To avoid potential terrestrial contamination effects, only meteorite falls and Antarctic finds are plotted. Data are from compilations for martian meteorites (47, 57–63), Mars Odyssey GRS data from ref. 64, MORB (65), and for OIB from GEOROC. The bulk silicate Earth has a K abundance of 240 ppm and a K/Th of 2,900 (66). Note the systematically high K/Th for martian surface materials measured by GRS compared with martian meteorites. Terrestrial rocks, especially MORB, exhibit a wide K/Th range overlapping with martian meteorite samples.An alternative means of examining the volatile history of Mars is by measuring the isotopic ratios of moderately volatile elements (MVE) in martian meteorites. Of the MVEs, which are defined as having 50% equilibrium condensation temperatures (50%T_c) of less than 1,335 K at a total pressure of 10⁻⁴ bar for a solar system gas composition (11), K is one of the most abundant (50% T_c = 1,006 K(11)). The isotopic ratios of K in igneous rocks from planetary bodies are insensitive to igneous processes [e.g., melting and fractional crystallization (12)] and secondary effects such as impact-induced vaporization (13) and eruptive degassing (14) and thus are a strong proxy for volatile depletion in planetary interiors. Here, the K isotope compositions of 20 martian meteorites are reported. These meteorites have previously been established to originate from Mars on the basis of triple-oxygen isotope systematics, trapped noble gas inventories, and the generally young crystallization ages (<1.34 Ga as with the majority of martian meteorites) (15–18). The 20 examined meteorites cover a range of rock types (basaltic, olivine-phyric, lherzolitic, and picritic shergottites, nakhlites [clinopyroxene-rich cumulates], a chassignite [cumulate dunite], and a basaltic crustal breccia [NWA 7034], SI Appendix, Table S1) and geochemical signatures (incompatible element-enriched, -intermediate, and -depleted shergottites). With the exception of the basaltic breccia NWA 7034, only observed meteorite falls and Antarctic meteorite finds were considered in order to avoid uncertainties related to terrestrial contamination and alteration, which commonly affect hot desert finds (19).     

Detection of serum tumor markers in multiple myeloma using the CLINPROT system

The discovery of biomarkers unique to multiple myeloma (MM) is of great importance to clinical practice. This study was designed to identify serum tumor marker candidates of MM in the mass range of 700-10000 Da. Serum samples from 48 MM patients and 74 healthy controls were collected and classified into a training dataset (MM/controls: 26/26) and a testing dataset (MM/controls: 22/48). Weak cation exchange magnetic beads, MALDI-TOF MS and analytic software in the CLINPROT system were used to do serum sample pre-fractionation, data acquisition and data analysis. Peak statistics were performed using Welch's t test. Mass spectra from the two model generation cohorts in the training dataset were analyzed by the Supervised Neural Network Algorithm (SNNA) in ClinProTools((TM)) to identify the mass peaks with the highest separation power. The resulting diagnostic model was subsequently validated in the testing dataset. A total of 89 discriminating mass peaks were detected by ClinProTools((TM)) in the range of 700-10000 Da using a signal to noise threshold of 3.0. Of these, 49 peaks had statistical significance (P < 0.0001) and four peaks with the highest separation power were picked up by SNNA to form a diagnostic model. This model achieved high sensitivity (86.36 %) and specificity (87.5 %) in the validation in the testing dataset. Using CLINPROT system and MB-WCX we found four novel biomarker candidates. The diagnostic model built by the four peaks achieved high sensitivity and specificity in validation. CLINPROT system is a powerful and reliable tool for clinical proteomic research.     

From the Cover: A 4,565-My-old andesite from an extinct chondritic protoplanet

The age of iron meteorites implies that accretion of protoplanets began during the first millions of years of the solar system. Due to the heat generated by ²⁶Al decay, many early protoplanets were fully differentiated with an igneous crust produced during the cooling of a magma ocean and the segregation at depth of a metallic core. The formation and nature of the primordial crust generated during the early stages of melting is poorly understood, due in part to the scarcity of available samples. The newly discovered meteorite Erg Chech 002 (EC 002) originates from one such primitive igneous crust and has an andesite bulk composition. It derives from the partial melting of a noncarbonaceous chondritic reservoir, with no depletion in alkalis relative to the Sun’s photosphere and at a high degree of melting of around 25%. Moreover, EC 002 is, to date, the oldest known piece of an igneous crust with a ²⁶Al-²⁶Mg crystallization age of 4,565.0 million years (My). Partial melting took place at 1,220 °C up to several hundred kyr before, implying an accretion of the EC 002 parent body ca. 4,566 My ago. Protoplanets covered by andesitic crusts were probably frequent. However, no asteroid shares the spectral features of EC 002, indicating that almost all of these bodies have disappeared, either because they went on to form the building blocks of larger bodies or planets or were simply destroyed.

Despite the large number of samples in the meteorite record that originate from the crust or mantle of rocky bodies (about 3,100 are known today), these rocks provide an incomplete picture of the diversity of the differentiated bodies that formed in the early solar system (1). Indeed, about 95% of these meteorites originate from only two bodies, with 75% coming from the crust of a single asteroid (possibly 4 Vesta) and the other 20% from the mantle of a presumably larger object, the now-destroyed ureilite parent body (2, 3). Thus, until recently, known achondritic lavas were essentially basalts (eucrites) from 4-Vesta and a handful of other basaltic rocks from unknown parent bodies [the angrites and some ungrouped achondrites such as Northwest Africa (NWA) 011 (4) or Ibitira (5)]. Although certainly not representative of the magmatic activity of all the planetesimals, these achondritic lavas strengthened the general view that their crusts were essentially basaltic in composition. However, the discovery of some rare achondrites of andesitic or trachyandesitic composition [e.g., Graves Nunataks 06128 and 016129 (6, 7), ALM-A (8), NWA 11119 (9)] demonstrated that the diversity of the lavas formed on protoplanets may have been more important than previously thought. Experimental studies motivated by these new meteorites have shown that the generation of silica-rich liquids is possible from the melting of chondrites (10–12). Thus, the formation of andesitic crust was possibly common on protoplanets, especially for those that were not Na and K depleted (12), contrary to what the meteorite record suggests. However, the processes that built such a crust, and the genesis of protoplanetary andesites are not well known due to the rarity of the samples. Here, we report on Erg Chech 002 (EC 002), a unique andesite achondrite found in the spring of 2020 in the Sahara. This meteorite is the oldest magmatic rock analyzed to date and sheds light on the formation of the primordial crusts that covered the oldest protoplanets.     

Stardust in meteorites

Primitive meteorites, interplanetary dust particles, and comets contain dust grains that formed around stars that lived their lives before the solar system formed. These remarkable objects have been intensively studied since their discovery a little over twenty years ago and they provide samples of other stars that can be studied in the laboratory in exquisite detail with modern analytical tools. The properties of stardust grains are used to constrain models of nucleosynthesis in red giant stars and supernovae, the dominant sources of dust grains that are recycled into the interstellar medium by stars.     

Ultrafast growth of wadsleyite in shock-produced melts and its implications for early solar system impact processes

We observed micrometer-sized grains of wadsleyite, a high-pressure phase of (Mg,Fe)₂SiO_4, in the recovery products of a shock experiment. We infer these grains crystallized from shock-generated melt over a time interval of <1 μs, the maximum time over which our experiment reached and sustained pressure sufficient to stabilize this phase. This rapid crystal growth rate (≈1 m/s) suggests that, contrary to the conclusions of previous studies of the occurrence of high-pressure phases in shock-melt veins in strongly shocked meteorites, the growth of high-pressure phases from the melt during shock events is not diffusion-controlled. Another process, such as microturbulent transport, must be active in the crystal growth process. This result implies that the times necessary to crystallize the high-pressure phases in shocked meteorites may correspond to shock pressure durations achieved on impacts between objects 1–5 m in diameter and not, as previously inferred, ≈1–5 km in diameter. These results may also provide another pathway for syntheses, via shock recovery, of some high-value, high-pressure phases.     

Questioning the preclinical paradigm: natural,extreme biology as an alternative discovery platform: A New Modest Proposal for Preventing the Children of the World from Being Burdened,Like Their Parents,by Disease and Making Beneficial Therapies (shamelessly co-opted from Dr. Swift)

The pace at which science continues to advance is astonishing. From cosmology, microprocessors, structural engineering, and DNA sequencing our lives are continually affected by science-based technology. However, progress in treating human ailments, especially age-related conditions such as cancer and Alzheimer''s disease, moves at a relative snail''s pace. Given that the amount of investment is not disproportionately low, one has to question why our hopes for the development of efficacious drugs for such grievous illnesses have been frustratingly unrealized. Here we discuss one aspect of drug development –rodent models – and propose an alternative approach to discovery research rooted in evolutionary experimentation. Our goal is to accelerate the conversation around how we can move towards more translative preclinical work.     

Search strategy has influenced the discovery rate of human viruses

A widely held concern is that the pace of infectious disease emergence has been increasing. We have analyzed the rate of discovery of pathogenic viruses, the preeminent source of newly discovered causes of human disease, from 1897 through 2010. The rate was highest during 1950–1969, after which it moderated. This general picture masks two distinct trends: for arthropod-borne viruses, which comprised 39% of pathogenic viruses, the discovery rate peaked at three per year during 1960–1969, but subsequently fell nearly to zero by 1980; however, the rate of discovery of nonarboviruses remained stable at about two per year from 1950 through 2010. The period of highest arbovirus discovery coincided with a comprehensive program supported by The Rockefeller Foundation of isolating viruses from humans, animals, and arthropod vectors at field stations in Latin America, Africa, and India. The productivity of this strategy illustrates the importance of location, approach, long-term commitment, and sponsorship in the discovery of emerging pathogens.     

Mid-Miocene cooling and the extinction of tundra in continental Antarctica

A major obstacle in understanding the evolution of Cenozoic climate has been the lack of well dated terrestrial evidence from high-latitude, glaciated regions. Here, we report the discovery of exceptionally well preserved fossils of lacustrine and terrestrial organisms from the McMurdo Dry Valleys sector of the Transantarctic Mountains for which we have established a precise radiometric chronology. The fossils, which include diatoms, palynomorphs, mosses, ostracodes, and insects, represent the last vestige of a tundra community that inhabited the mountains before stepped cooling that first brought a full polar climate to Antarctica. Paleoecological analyses, ⁴⁰Ar/³⁹Ar analyses of associated ash fall, and climate inferences from glaciological modeling together suggest that mean summer temperatures in the region cooled by at least 8°C between 14.07 ± 0.05 Ma and 13.85 ± 0.03 Ma. These results provide novel constraints for the timing and amplitude of middle-Miocene cooling in Antarctica and reveal the ecological legacy of this global climate transition.     

Study on Photocatalytic Performance of Ag/TiO2 Modified Cement Mortar

In this paper, Ag-TiO₂ photocatalysts with different Ag contents (1 mol%–5 mol%) were prepared and applied to cement mortar. The photocatalytic performance of Ag-TiO₂ and photocatalytic cement mortar under UV light and simulated solar light was evaluated. The results showed that Ag loading on the surface of TiO₂ could reduce its band gap width and increase its absorbance in the visible region, and 2% Ag-TiO₂ had the highest photocatalytic activity under UV light, the degradation rate of methyl orange (MO) was 95.5% at 30 min, and the first-order reaction constant k was 0.0980 min⁻¹, which was 61.7% higher than that of TiO₂, and 5% Ag-TiO₂ had the highest photocatalytic activity under solar light, the degradation rate of methylene blue (MB) was 69.8% at 40 min, and the first-order reaction constant k was 0.0294 min⁻¹, which was 90.9% higher than that of TiO₂. The photocatalytic mortar prepared by the spraying method has high photocatalytic performance, The MO degradation rate of sample S2 under UV light was 87.5% after 120 min, MB degradation rate of sample S5 under solar light was 75.4% after 120 min. The photocatalytic reaction conforms to the zero-order reaction kinetics, which was 1.5 times–3.3 times higher than that of the mixed samples and has no effect on the mechanical properties of mortar.     

The Prognosis of Nasopharyngeal Carcinoma Involving Masticatory Muscles: A Retrospective Analysis for Revising T Subclassifications

This work is a retrospective study of magnetic resonance imaging (MRI) and T-stage subclassifications of nasopharyngeal carcinoma (NPC) involving the masticatory muscles (MMs). We examined how involvement of MMs influences the clinical T-stage classifications and the survival outcomes of NPC patients.MRI data as well as the medical records from 816 NPC patients were analyzed retrospectively. All cases were restaged according to the seventh edition of American Joint Committee on Cancer staging system criteria. The overall survival (OS), local relapse-free survival (LRFS), and distant metastasis-free survival (DMFS) were analyzed by the Kaplan–Meier method, and their survival outcomes between different degrees of MM involvement and different T classifications were compared by using the log-rank test. All statistical analyses were conducted on SPSS 18.0 software. P > 0.05 was considered significant.Of the 816 NPC patients analyzed, 283 (34.68%) had tumors that involved MMs. All of those 283 patients involved the medial pterygoid muscle, and 125 cases (15.32%) involved the lateral pterygoid muscle. Multivariate analysis identified MM involvement as an independent prognostic factor for patient''s OS (P = 0.007) and LRFS (P = 0.024). MM involvement significantly correlated with a lower OS and LRFS (P < 0.01). In addition, compared with concurrent involvement of the medial and lateral pterygoid muscle, the medial pterygoid muscle involvement correlated with a higher OS and LRFS (P < 0.05). Among NPC patients, T-classifications 1 to 4 usually predicted the ultimate OS, LRFS, and DMFS (P > 0.1), unless the cancer involved the lateral pterygoid muscle.NPC involving the lateral pterygoid muscle presents a worse survival outcome than that involving the medial pterygoid muscle. Any cancer involving the lateral pterygoid muscle should be classified in a higher T-stage subclassification.