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From supernovae to planets: The view from meteorites and IDPs
Chondritic meteorites and IDPs retain a record of the prehistory and early history of the Solar System. Chondrites are derived from the asteroid belt, while IDPs probably have both cometary and asteroidal origins. Chondrites and their components contained relatively high levels of short-lived radionuclides when they formed. Some, like 60 Fe, require a stellar source, while others may have formed via energetic particle irradiation in the Solar System. The half-lives of some of the radionuclides are so short (0.1-0.7 My) that if they had a stellar source, this source probably triggered the formation of the Solar System. The high abundance of crystalline circumstellar silicates in IDPs and meteorites, and the relatively low abundance of interstellar organic matter in CI chondrites may result from the thermal processing of interstellar dust seen in YSOs. The oldest dated Solar System objects are the refractory inclusions. The more abundant chondrules seem to have begun forming 1-2 My after refractory inclusions, although there is evidence that chondrules in the CV chondrites began forming contemporaneously with refractory inclusions. Both refractory inclusions and chondrules appear to be the products of transient heating events. The mechanism for making refractory inclusions is uncertain, but in most models refractory inclusions form sunward of the asteroid belt and are then transported outwards either in energetic winds or via turbulent diffusion. At present, the most promising mechanism for making chondrules is shock heating in the asteroid belt. Each chondrite group contains a chemically and/or physically distinct population of chondrules and refractory inclusions. To preserve their distinct chondrule properties from being erased by turbulent diffusion, it is argued that chondrites must have accreted soon after their chondrules formed. However, the variation in the properties of refractory inclusions between chondrites is unexplained. To explain the evidence for aqueous alteration in most chondrites, chondrite formation occurred in the T Tauri phase when temperatures in the asteroid belt allowed for ice to be stable.
Meteorites from the outer solar system
2008
We investigate the possibility that a small fraction of meteorites originate from the outer solar system, ie, from the Kuiper belt, the Oort cloud, or from the Jupiter-family comet reservoir. Dynamical studies and meteor observations show that it is possible for cometary solid fragments to reach Earth with a velocity not unlike that of asteroidal meteorites. Cosmochemical data and orbital studies identify CI1 chondrites as the best candidates for being cometary meteorites.
From Supernovae to Planets: The View from Meteorites and Interplanetary Dust Particles
Chondritic meteorites and IDPs retain a record of the prehistory and early history of the Solar System. Chondrites are derived from the asteroid belt, while IDPs probably have both cometary and asteroidal origins. Chondrites and their components contained relatively high levels of short-lived radionuclides when they formed. Some, like 60 Fe, require a stellar source, while others may have formed via energetic particle irradiation in the Solar System. The half-lives of some of the radionuclides are so short (0.1-0.7 My) that if they had a stellar source, this source probably triggered the formation of the Solar System. The high abundance of crystalline circumstellar silicates in IDPs and meteorites, and the relatively low abundance of interstellar organic matter in CI chondrites may result from the thermal processing of interstellar dust seen in YSOs. The oldest dated Solar System objects are the refractory inclusions. The more abundant chondrules seem to have begun forming 1-2 My after refractory inclusions, although there is evidence that chondrules in the CV chondrites began forming contemporaneously with refractory inclusions. Both refractory inclusions and chondrules appear to be the products of transient heating events. The mechanism for making refractory inclusions is uncertain, but in most models refractory inclusions form sunward of the asteroid belt and are then transported outwards either in energetic winds or via turbulent diffusion. At present, the most promising mechanism for making chondrules is shock heating in the asteroid belt. Each chondrite group contains a chemically and/or physically distinct population of chondrules and refractory inclusions. To preserve their distinct chondrule properties from being erased by turbulent diffusion, it is argued that chondrites must have accreted soon after their chondrules formed. However, the variation in the properties of refractory inclusions between chondrites is unexplained. To explain the evidence for aqueous alteration in most chondrites, chondrite formation occurred in the T Tauri phase when temperatures in the asteroid belt allowed for ice to be stable.
Protostellar Winds and Chondritic Meteorites
Space Sciences Series of ISSI, 2000
We discuss the interaction between the magnetosphere of a young star and its surrounding accretion disk. We consider how an X-wind can be driven magnetocentrifugally from the inner edge of the disk where accreting gas is diverted onto stellar field lines either to flow onto the Sun or to be flung outwards with the wind. The X-wind satisfies many observational tests concerning optical jets, Herbig-Haro objects, and molecular outflows. Connections may exist between primitive solar system materials and X-winds. Chondrules and calcium-aluminum-rich inclusions (CAIs) experienced short melting events uncharacteristic of the asteroid belt where meteorites originate. The inner edge of the solar nebula has the shortest orbital timescale available to the system, a few days. Protosolar flares introduce another timescale, tens of minutes to hours. CAIs may form when solids are lifted from shaded portions of the disk close to the Sun and are exposed to its intense light for a day or so before they are flung by the X-wind to much larger distances. Chondrules were melted, perhaps many times, by flares at larger distances from the Sun before being launched and annealed, but not remelted, in the X-wind. Aerodynamic sorting explains the narrow range of sizes with which CAIs and chondrules are found in chondritic meteorites. Flare-generated cosmic-rays may induce spallation reactions that produce some of the short-lived radioactivities associated with primitive solar system rocks.
2007
Chondrules in chondritic meteorites record the earliest stages of formation of the solar system, potentially providing information about the magnitude of early magnetic fields and early physical and chemical conditions. Using first-order reversal curves (FORCs), we map the coercivity distributions and interactions of 32 chondrules from the Allende, Karoonda, and Bjurbole meteorites. Distinctly different distributions and interactions exist for the three meteorites. The coercivity distributions are lognormal shaped, with Bjurbole distributions being bimodal or trimodal. The highest-coercivity mode in the Bjurbole chondrules is derived from tetrataenite, which interacts strongly with the lower-coercivity grains in a manner unlike that seen in terrestrial rocks. Such strong interactions have the potential to bias paleointensity estimates. Moreover, because a significant portion of the coercivity distributions for most of the chondrules is <10 mT, low-coercivity magnetic overprints are common. Therefore paleointensities based on the REM method, which rely on ratios of the natural remanent magnetization (NRM) to the saturation isothermal remanent magnetization (IRM) without magnetic cleaning, will probably be biased. The paleointensity bias is found to be about an order of magnitude for most chondrules with low-coercivity overprints. Paleointensity estimates based on a method we call REMc, which uses NRM/IRM ratios after magnetic cleaning, avoid this overprinting bias. Allende chondrules, which are the most pristine and possibly record the paleofield of the early solar system, have a mean REMc paleointensity of 10.4 mT. Karoonda and Bjurbole chondrules, which have experienced some thermal alteration, have REMc paleointensities of 4.6 and 3.2 mT, respectively.
Samples of the Solar System: Recent Developments
Protostars and Planets VI, 2014
We review some of the major findings in cosmochemistry since the Protostars and Planets V meeting: (1) the results of the sample-return space missions Genesis, Stardust, and Hayabusa, which yielded the oxygen and nitrogen isotopic composition of the Sun, evidence for significant radial transport of solids in the protoplanetary disk and the chondrite-comet connection, and the connection between ordinary chondrites and S-type asteroids, respectively; (2) the D/H ratio of chondritic water as a test of the Nice and Grand Tack dynamical models and implications for the origin of the Earth's volatiles; (3) the origin, initial abundances, and distribution of the short-lived radionuclides 10 Be, 26 Al, 36 Cl, 41 Ca, 53 Mn, 60 Fe in the early Solar System; (4) the absolute (U-Pb) and relative (short-lived radionuclide) chronology of early Solar System processes; (5) the astrophysical setting of the Solar System formation; (6) the formation of chondrules under highly nonsolar conditions; and (7) the origin of enstatite chondrites.
Early scattering of the solar protoplanetary disk recorded in meteoritic chondrules
Science Advances, 2016
Meteoritic chondrules are submillimeter spherules representing the major constituent of nondifferentiated planetesimals formed in the solar protoplanetary disk. The link between the dynamics of the disk and the origin of chondrules remains enigmatic. Collisions between planetesimals formed at different heliocentric distances were frequent early in the evolution of the disk. We show that the presence, in some chondrules, of previously unrecognized magnetites of magmatic origin implies the formation of these chondrules under impact-generated oxidizing conditions. The three oxygen isotopes systematic of magmatic magnetites and silicates can only be explained by invoking an impact between silicate-rich and ice-rich planetesimals. This suggests that these peculiar chondrules are by-products of the early mixing in the disk of populations of planetesimals from the inner and outer solar system.
Meteorites: Messengers from the Early Solar System
CHIMIA International Journal for Chemistry, 2010
Meteorites are fragments from solar system bodies, dominantly asteroids. A small fraction is derived from the Moon and from Mars. These rocks tell a rich history of the early solar system and range from solids little changed since the earliest phases of solid matter condensation in the solar nebula (chondrites) to material representing asteroidal metamorphism and melting, impact processes on the Moon and even aqueous alteration near the surface of Mars. Meteorites are very rare. Currently many meteorites result from searches in Antarctica and the hot deserts of North Africa and Arabia. The present high find rate likely represents a unique short-term event, asking for a careful management of this scarce scientific resource.