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The formation of planets in our solar system encompassed various stages of accretion of planetesimals that formed in the protoplanetary disk within the first few million years at different distances to the sun. Their chemical diversity is reflected by compositionally variable meteorite groups from different parent bodies. There is general consensus that their formation location is roughly constrained by a dichotomy of nucleosynthetic isotope anomalies, relating carbonaceous (C) meteorite parent bodies to the outer protoplanetary disk and the non-carbonaceous (NC) parent bodies to an origin closer to the sun. It is a common idea, that in these inner parts of the protoplanetary disks, planetesimal accretion processes were faster. Testing such scenarios requires constraining formation ages of meteorite parent bodies. Although isotopic age dating can yield precise formation ages of individual mineral constituents of meteorites, such ages frequently represent mineral cooling ages that can postdate planetesimal formation by millions or tens of millions of years, depending on the cooling history of individual planetesimals at different depths. Nevertheless, such cooling ages provide a detailed thermal history which can be fitted by thermal evolution models that constrain the formation age of individual parent bodies. Here we apply state-of-the-art thermal evolution models to constrain planetesimal formation times particular in the outer solar system formation region of C meteorites. We infer a temporally distributed accretion of various parent bodies from < 0.6 Ma to ≈ 4 Ma after solar system formation, with 3.7 Ma and 2.5 - 2.75 Ma for the parent bodies of CR1-3 chondrites and the Flensburg carbonaceous chondrite, and < 0.6 and < 0.7 Ma for the parent bodies of differentiated achondrites NWA 6704 and NWA 011, respectively. This implies that accretion processes in the C reservoir started as early as in the NC reservoir and were operating throughout typical protoplanetary disk lifetimes, thereby producing differentiated parent bodies with carbonaceous compositions in addition to undifferentiated C chondrite parent bodies. The accretion times correlate inversely with the degree of the meteorites’ alteration, metamorphism, or differentiation. The accretion times for the CM, CI, Ryugu, and Tafassite parent bodies of 3.8 Ma, 3.8 Ma, 1 - 3 Ma, and 1.1 Ma, respectively, fit well into this correlation in agreement with the thermal and alteration conditions suggested by these meteorites. Our results indicate that individual planetesimals formed rapidly (i.e., within < 1 Ma), however, distinct planetesimals formed recurrently throughout the total lifetime of the protoplanetary disk. Rapid individual formation is consistent with streaming instabilities assisted by gravitational collapse. However, obviously not the total dust inventory was consumed at early disk evolution stages, so there must have been some delay mechanisms, e.g. collisional destruction of precursor aggregates due to high impact velocities induced by radial drift phenomena. This counterbalance enabled late ( > 2 - 3 Ma) accretion of C planetesimals beyond the snow line which escaped severe planetesimal heating and volatile loss, hence, preserving their volatiles, especially water. Only this delayed formation of water-rich planetesimals allowed Earth to accrete sufficient water to become a habitable planet, preventing it from being a bone dry planet.

Saturn’s moon Enceladus harbours a global water ocean 1 , which lies under an ice crust and above a rocky core 2 . Through warm cracks in the crust 3 a cryo-volcanic plume ejects ice grains and vapour into space 4 – 7 that contain materials originating from the ocean 8 , 9 . Hydrothermal activity is suspected to occur deep inside the porous core 10 – 12 , powered by tidal dissipation 13 . So far, only simple organic compounds with molecular masses mostly below 50 atomic mass units have been observed in plume material 6 , 14 , 15 . Here we report observations of emitted ice grains containing concentrated and complex macromolecular organic material with molecular masses above 200 atomic mass units. The data constrain the macromolecular structure of organics detected in the ice grains and suggest the presence of a thin organic-rich film on top of the oceanic water table, where organic nucleation cores generated by the bursting of bubbles allow the probing of Enceladus’ organic inventory in enhanced concentrations. The detection of complex organic molecules with masses higher than 200 atomic mass units in ice grains emitted from Enceladus indicates the presence of a thin organic-rich layer on top of the moon’s subsurface ocean.

The history of accretion and differentiation processes in the planetesimals is provided by various groups of meteorites. Sampling different parent body layers, they reveal the circumstances of the metal–silicate segregation and the internal structures of the protoplanets. The ungrouped achondrite Erg Chech 002 (EC 002) added to the suite of samples from primitive igneous crusts. Here we present models that utilize thermochronological data for EC 002 and fit the accretion time and size of its parent body to these data. The U-corrected Pb–Pb pyroxene, Pb–Pb phosphate, and Ar–Ar ages used imply a best-fit planetesimal with a radius of 20–30 km that formed at 0.1 Ma after calcium-aluminum-rich inclusions. Its interior melted early and differentiated by 0.5 Ma, allowing core and mantle formation with a transient lower mantle magma ocean and a melt fraction of <25% at the meteorite layering depth. EC 002 formed from this melt at a depth of 0.8 km in a partially differentiated region covered by an undifferentiated crust. By simulating collisions with impactors of different sizes and velocities, we analyzed the minimum ejection conditions of EC 002 from its original parent body and the surface composition of the impact site. The magma ocean region distinct from the layering depth of EC 002 implies that it was not involved in the EC 002 genesis. Our models estimate closure temperatures for the Al–Mg ages as 1030–1200 K. A fast parent body cooling attributes the late Ar–Ar age to a local reheating by another, late impact.

Shock-induced melt veins in amphibolites from the Nördlinger Ries often have chemical compositions that are similar to bulk rock (i.e., basaltic), but there are other veins that are confined to chlorite-rich cracks that formed before the impact and these are poor in Ca and Na. Majoritic garnets within the shock veins show a broad chemical variation between three endmembers: (1) VIII M 2 + 3 VI Al 2 ( IV SiO 4 ) 3  (normal garnet, Grt), (2) VIII M 2 + 3 VI [ M 2 + ( Si,Ti ) ] ( IV SiO 4 ) 3  (majorite, Maj), and (3) VIII ( Na M 2 + 2 ) VI [ ( Si,Ti ) Al ] ( IV SiO 4 ) 3 (Na-majorite 50 Grt 50 ), whereby M 2+  = Mg 2+ , Fe 2+ , Mn 2+ , Ca 2+ . In particular, we observed a broad variation in VI (Si,Ti) which ranges from 0.12 to 0.58 cations per formula unit (cpfu). All these majoritic garnets crystallized during shock pressure release at different ultrahigh pressures. Those with high VI (Si,Ti) (0.36–0.58 cpfu) formed at high pressures and temperatures from amphibole-rich melts, while majoritic garnets with lower VI (Si,Ti) of 0.12–0.27 cpfu formed at lower pressures and temperatures from chlorite-rich melts. Furthermore, majoritic garnets with intermediate values of VI (Si,Ti) (0.24–0.39) crystallized from melts with intermediate contents of Ca and Na. To the best of our knowledge the ‘MORB-type’ Ca–Na-rich majoritic garnets with maximum contents of 2.99 wt% Na 2 O and calculated crystallisation pressures of 16–18 GPa are the most extreme representatives ever found in terrestrial shocked materials. At the Ries, the duration of the initial contact and compression stage at the central location of impact is estimated to only ~ 0.1 s. We used a ~ 200-µm-thick shock-induced vein in a moderately shocked amphibolite to model its pressure–temperature–time ( P – T – t ) path. The graphic model manifests a peak temperature of ~ 2600 °C for the vein, continuum pressure lasting for ~ 0.02 s, a quench duration of ~ 0.02 s and a shock pulse of ~ 0.038 s. The small difference between the continuum pressure and the pressure of majoritic garnet crystallization underlines the usefulness of applying crystallisation pressures of majoritic garnets from metabasites for calculation of dynamic shock pressures of host rocks. Majoritic garnets of chlorite provenance, however, are not suitable for the determination of continuum pressure since they crystallized relatively late during shock release. An extraordinary glass- and majorite-bearing amphibole fragment in a shock-vein of one amphibolite documents the whole unloading path.

Our Solar System formed approximately 4.6 billion years ago from the collapse of a dense core inside an interstellar molecular cloud. The subsequent formation of solid bodies took place rapidly. The period of &<10 million years over which planetesimals were assembled can be investigated through the study of meteorites. Although some planetesimals differentiated and formed metallic cores like the larger terrestrial planets, the parent bodies of undifferentiated chondritic meteorites experienced comparatively mild thermal metamorphism that was insufficient to separate metal from silicate. There is debate about the nature of the heat source as well as the structure and cooling history of the parent bodies. Here we report a study of 244Pu fission-track and 40Ar-39Ar thermochronologies of unshocked H chondrites, which are presumed to have a common, single, parent body. We show that, after fast accretion, an internal heating source (most probably 26Al decay) resulted in a layered parent body that cooled relatively undisturbed: rocks in the outer shells reached lower maximum metamorphic temperatures and cooled faster than the more recrystallized and chemically equilibrated rocks from the centre, which needed approximately 160 Myr to reach 390K.

Noble gases are important tracers of planetary accretion and acquisition of volatiles to planetary atmospheres and interiors. Earth’s mantle hosts solar-type helium and neon for which 20 Ne/ 22 Ne ratios advocate either incorporation of solar wind irradiated solids or solar nebula gas dissolution into an early magma ocean. However, the exact source location of primordial signatures remains unclear. Here we use high-resolution stepwise heating gas extraction experiments to analyse interior samples of the iron meteorite Washington County and find that they contain striking excesses of solar helium and neon. We infer that the Washington County protolith was irradiated by solar wind and that implanted noble gases were partitioned into segregating metal melts. The corollary that solar signatures are able to enter the cores of differentiated planetesimals and protoplanets validates hypotheses that Earth’s core may have incorporated solar noble gases and may be contributing to the solar signatures observed in Earth’s mantle.

Amphibolite clasts in the suevite of the Ries impact crater contain shock-induced melt veins (SMVs) with high-pressure phases such as majoritic garnet, jadeitic clinopyroxene and others. In addition, heat conduction from hot SMVs into adjacent rock portions locally produced further high P – T melt pools. These melts were preferentially generated in rock domains, where the SMVs cross older (‘pre-Ries’) veinlets with analcime or prehnite and larger grains of sericitized plagioclase. Melting of such chemically different local bulk systems (Na-, Ca-, Ca-Na- and K-Na-rich) was facilitated by low solidus temperatures of the original secondary OH-bearing phases. From the resulting shock-induced melts, liebermannite, kokchetavite, jadeite, nonstoichiometric and albitic jadeite, grossular, vuagnatite, lawsonite + coesite, and clinozoisite crystallized during pressure release. Vuagnatite is now proven to be a genuine high-pressure phase. Its ubiquitous distance of 20–35 μm from the hot shock veins suggests a temperature sensitivity typical for an OH-bearing phase. In local Na-rich melts albitic jadeite appears instead of the assemblage jadeite + SiO 2 . Liebermannite, a dense polymorph of K-feldspar was identified by Raman spectroscopy. After stishovite, liebermannite constitutes the second known high-pressure phase in the Ries that contains silicon exclusively in six-fold coordination. The KAlSi 3 O 8 -polymorph kokchetavite was formed in alkali-rich melt glasses. Pressure and temperature values in the range of about 8–11 GPa and ~ 800–1100 °C were estimated from the chemical compositions of locally occurring majoritic garnets (Si = 3.21–3.32 and 3.06–3.10 apfu), respectively, and the presence of fine-grained aggregates of lawsonite and coesite. Generally, the neighboring areas of the veins are characterized by a sequence of variable high-pressure phases documenting strongly falling P–T conditions with increasing distance from the vein. These novel features enlighten the dynamic event during passage of a shock wave.

Low-albedo asteroids preserve a record of the primordial Solar System planetesimals and the conditions in which the solar nebula was active. However, the origin and evolution of these asteroids are not well constrained. Here we measured visible and near-infrared (about 0.5–4.0 μm) spectra of low-albedo asteroids in the mid-outer main belt. We show that numerous large (diameter >100 km) and dark (geometric albedo <0.09) asteroids exterior to the dwarf planet Ceres’ orbit share the same spectral features, and presumably compositions, as Ceres. We also developed a thermal evolution model that demonstrates that these Ceres-like asteroids have highly porous interiors, accreted relatively late at 1.5–3.5 Myr after the formation of calcium–aluminium-rich inclusions, and experienced maximum interior temperatures of <900 K. Ceres-like asteroids are localized in a confined heliocentric region between about 3.0 au and 3.4 au, but were probably implanted from more distant regions of the Solar System during the giant planet’s dynamical instability.The large, low-albedo asteroids in the main belt between 3.0 au and 3.4 au share spectral characteristics and history with Ceres. Accreted in different parts of the outer Solar System, they might have been implanted into the main belt by the dynamic upheaval created by the giant planets’ instability.

We present the first comprehensive noble gas study on eclogites. The four eclogite samples were recovered during the Chinese Continental Scientific Drilling and are from two distinct profile depth sections differing in their degree of interaction with meteoric water, based on their δ 18 O-values (surface related and of mantle-type). Hence, noble gas analyses offer the potential to further discriminate between shallow (meteoric) and deep (mantle) fluid sources. Noble gas compositions reveal typical crustal fluid compositions, characterized by a variable mixture of atmospheric gases with significant contributions of nucleogenic neon, radiogenic 4 He*, radiogenic 40 Ar*, fissiogenic 131–136 Xe, and presumably bariogenic 131 Xe, but no significant addition of mantle gases. This signature can be also considered to represent one endmember component of eclogitic diamonds. Concentrations of non-radiogenic noble gases are rather low, with depletion of light relative to the heavier noble gases. Eclogites from lower depth which experienced a higher degree of interaction with meteoric water also showed higher contributions of atmospheric gas compared with eclogites recovered from greater depth. This is interpreted to result from interaction with high-salinity fluids during ultrahigh pressure (UH P ). It demonstrates that the atmospheric noble gas abundance is a proxy for interaction with surface related fluids. 40 Ar/ 39 Ar (inverse) isochron ages of two phengite separates (241.2 ± 0.4 Ma and 275.0 ± 1.8 Ma, 1 σ -errors) predate the main phase of UH P metamorphism (ca. 220 Ma). Biotite yields an integrated age of about 1100 Ma. These age values are interpreted to reflect the likely addition of excess 40 Ar without any chronological meaning.