Fragments of Late Eocene Earth-impacting asteroids linked to disturbance of asteroid belt (original) (raw)
Related papers
A late Miocene dust shower from the break-up of an asteroid in the main belt
Nature, 2006
Throughout the history of the Solar System, Earth has been bombarded by interplanetary dust particles (IDPs), which are asteroid and comet fragments of diameter approximately 1-1,000 microm. The IDP flux is believed to be in quasi-steady state: particles created by episodic main belt collisions or cometary fragmentation replace those removed by comminution, dynamical ejection, and planetary or solar impact. Because IDPs are rich in 3He, seafloor sediment 3He concentrations provide a unique means of probing the major events that have affected the IDP flux and its source bodies over geological timescales. Here we report that collisional disruption of the >150-km-diameter asteroid that created the Veritas family 8.3 +/- 0.5 Myr ago also produced a transient increase in the flux of interplanetary dust-derived 3He. The increase began at 8.2 +/- 0.1 Myr ago, reached a maximum of approximately 4 times pre-event levels, and dissipated over approximately 1.5 Myr. The terrestrial IDP accretion rate was overwhelmingly dominated by Veritas family fragments during the late Miocene. No other event of this magnitude over the past approximately 10(8) yr has been deduced from main belt asteroid orbits. One remarkably similar event is present in the 3He record 35 Myr ago, but its origin by comet shower or asteroid collision remains uncertain.
Science Advances
The breakup of the L-chondrite parent body in the asteroid belt 466 million years (Ma) ago still delivers almost a third of all meteorites falling on Earth. Our new extraterrestrial chromite and 3He data for Ordovician sediments show that the breakup took place just at the onset of a major, eustatic sea level fall previously attributed to an Ordovician ice age. Shortly after the breakup, the flux to Earth of the most fine-grained, extraterrestrial material increased by three to four orders of magnitude. In the present stratosphere, extraterrestrial dust represents 1% of all the dust and has no climatic significance. Extraordinary amounts of dust in the entire inner solar system during >2 Ma following the L-chondrite breakup cooled Earth and triggered Ordovician icehouse conditions, sea level fall, and major faunal turnovers related to the Great Ordovician Biodiversification Event.
2007
Radiochronometry of L chondritic meteorites yields a rough age estimate for a major collision in the asteroid belt about 500 Myr ago. Fossil meteorites from Sweden indicate a highly increased influx of extraterrestrial matter in the Middle Ordovician ~480 Myr ago. An association with the L-chondrite parent body event was suggested, but a definite link is precluded by the lack of more precise radiometric ages. Suggested ages range between 450 ± 30 Myr and 520 ± 60 Myr, and can neither convincingly prove a single breakup event, nor constrain the delivery times of meteorites from the asteroid belt to Earth. Here we report the discovery of multiple 40 Ar-39 Ar isochrons in shocked L chondrites, particularly the regolith breccia Ghubara, that allow the separation of radiogenic argon from multiple excess argon components. This approach, applied to several L chondrites, yields an improved age value that indicates a single asteroid breakup event at 470 ± 6 Myr, fully consistent with a refined age estimate of the Middle Ordovician meteorite shower at 467.3 ± 1.6 Myr (according to A Geologic Time Scale 2004). Our results link these fossil meteorites directly to the L-chondrite asteroid destruction, rapidly transferred from the asteroid belt. The increased terrestrial meteorite influx most likely involved larger projectiles that contributed to an increase in the terrestrial cratering rate, which implies severe environmental stress.
An asteroid breakup 160 Myr ago as the probable source of the K/T impactor
Nature, 2007
The terrestrial and lunar cratering rate is often assumed to have been nearly constant over the past 3 Gyr. Different lines of evidence, however, suggest that the impact flux from kilometre-sized bodies increased by at least a factor of two over the long-term average during the past approximately 100 Myr. Here we argue that this apparent surge was triggered by the catastrophic disruption of the parent body of the asteroid Baptistina, which we infer was a approximately 170-km-diameter body (carbonaceous-chondrite-like) that broke up 160(-20)+30Myr ago in the inner main asteroid belt. Fragments produced by the collision were slowly delivered by dynamical processes to orbits where they could strike the terrestrial planets. We find that this asteroid shower is the most likely source (>90 per cent probability) of the Chicxulub impactor that produced the Cretaceous/Tertiary (K/T) mass extinction event 65 Myr ago.
Geochimica et Cosmochimica Acta, 2009
We evaluate initial ( 26 Al/ 27 Al) I , ( 53 Mn/ 55 Mn) I , and ( 182 Hf/ 180 Hf) I ratios, together with 207 Pb/ 206 Pb ages for igneous differentiated meteorites and chondrules from ordinary chondrites for consistency with radioactive decay of the parent nuclides within a common, closed isotopic system, i.e., the early solar nebula. The relative initial isotopic abundances of 26 Al, 53 Mn, and 182 Hf in differentiated meteorites and chondrules are consistent with decay from common solar system initial values, here denoted by I(Al) SS , I(Mn) SS , and I(Hf) SS, respectively. I(Mn) SS and I(Hf) SS = 9.1 ± 1.7 Â 10 À6 and 1.07 ± 0.08 Â 10 À4 , respectively, correspond to ''canonical" I(Al) SS = 5.1 Â 10 À5 . I(Hf) SS so determined is consistent with I(Hf) SS = 9.72 ± 0.44 Â 10 À5 directly determined from an internal Hf-W isochron for CAI minerals. I(Mn) SS is within error of the lowest value directly measured for CAIs. We suggest that erratically higher values measured for CAIs in carbonaceous chondrites may reflect proton irradiation of unaccreted CAIs by the early Sun after other asteroids destined for melting by 26 Al decay had already accreted. The 53 Mn incorporated within such asteroids would have been shielded from further ''local" spallogenic contributions from within the solar system. The relative initial isotopic abundances of the short-lived nuclides are less consistent with the 207 Pb/ 206 Pb ages of the corresponding materials than with one another. The best consistency of shortand long-lived chronometers is obtained for ( 182 Hf/ 180 Hf) I and the 207 Pb/ 206 Pb ages of angrites. ( 182 Hf/ 180 Hf) I decreases with decreasing 207 Pb/ 206 Pb ages at the rate expected from the 8.90 ± 0.09 Ma half-life of 182 Hf. The model solar system age thus determined is T SS,Hf-W = 4568.3 ± 0.7 Ma. ( 26 Al/ 27 Al) I and ( 53 Mn/ 55 Mn) I are less consistent with 207 Pb/ 206 Pb ages of the corresponding meteorites, but yield T SS,Mn-Cr = 4568.2 ± 0.5 Ma relative to I(Al) SS = 5.1 Â 10 À5 and a 207 Pb/ 206 Pb age of 4558.55 ± 0.15 Ma for the LEW86010 angrite. The Mn-Cr method with I(Mn) SS = 9.1 ± 1.7 Â 10 À6 is useful for dating accretion (if identified with chondrule formation), primary igneous events, and secondary mineralization on asteroid parent bodies. All of these events appear to have occurred approximately contemporaneously on different asteroid parent bodies. For I(Mn) SS = 9.1 ± 1.7 Â 10 À6 , parent body differentiation is found to extend at least to 5Mapost−TSS,i.e.,untildifferentiationoftheangriteparentbody5 Ma post-T SS , i.e., until differentiation of the angrite parent body 5Mapost−TSS,i.e.,untildifferentiationoftheangriteparentbody4563.5 Ma ago, or 4564.5Maagousingthedirectlymeasured207Pb/206PbagesoftheD′Orbigny−clanangrites.The4564.5 Ma ago using the directly measured 207 Pb/ 206 Pb ages of the D'Orbigny-clan angrites. The 4564.5Maagousingthedirectlymeasured207Pb/206PbagesoftheD′Orbigny−clanangrites.The1 Ma difference is characteristic of a remaining inconsistency for the D'Orbigny-clan between the Al-Mg and Mn-Cr chronometers on one hand, and the 207 Pb/ 206 Pb chronometer on the other. Differentiation of the IIIAB iron meteorite and ureilite parent bodies probably occurred slightly later than for the angrite parent body, and at nearly the same time as one another as shown by the Mn-Cr ages of IIIAB irons and ureilites, respectively. The latest recorded epi-0016-7037/$ -see front matter Published by Elsevier Ltd. Geochimica et Cosmochimica Acta 73 (2009) 5115-5136 sodes of secondary mineralization are for carbonates on the CI carbonaceous chondrite parent body and fayalites on the CV carbonaceous chondrite parent body, both extending to $10 Ma post-T SS . Published by Elsevier Ltd.
Hf–W chronology of the accretion and early evolution of asteroids and terrestrial planets
Geochimica et Cosmochimica Acta, 2009
The 182 Hf-182 W systematics of meteoritic and planetary samples provide firm constraints on the chronology of the accretion and earliest evolution of asteroids and terrestrial planets and lead to the following succession and duration of events in the earliest solar system. Formation of Ca,Al-rich inclusions (CAIs) at 4568.3 ± 0.7 Ma was followed by the accretion and differentiation of the parent bodies of some magmatic iron meteorites within less than 1Myr.ChondrulesfromHchondritesformed1.7±0.7MyrafterCAIs,aboutcontemporaneouslywithchondrulesfromLandLLchondritesasshownbytheir26Al−26Mgages.Somemagmatismontheparentbodiesofangrites,eucrites,andmesosideritesstartedassoonas1 Myr. Chondrules from H chondrites formed 1.7 ± 0.7 Myr after CAIs, about contemporaneously with chondrules from L and LL chondrites as shown by their 26 Al-26 Mg ages. Some magmatism on the parent bodies of angrites, eucrites, and mesosiderites started as soon as 1Myr.ChondrulesfromHchondritesformed1.7±0.7MyrafterCAIs,aboutcontemporaneouslywithchondrulesfromLandLLchondritesasshownbytheir26Al−26Mgages.Somemagmatismontheparentbodiesofangrites,eucrites,andmesosideritesstartedassoonas3 Myr after CAI formation and may have continued until 10Myr.Asimilartimescaleisobtainedforthehigh−temperaturemetamorphicevolutionoftheHchondriteparentbody.Thermalmodelingcombinedwiththeseageconstraintsrevealsthatthedifferentthermalhistoriesofmeteoriteparentbodiesprimarilyreflecttheirinitialabundanceof26Al,whichisdeterminedbytheiraccretionage.Impact−relatedprocesseswereimportantinthesubsequentevolutionofasteroidsbutdonotappeartohaveinducedlarge−scalemelting.Forinstance,Hf−WagesforeucritemetalspostdateCAIformationby10 Myr. A similar timescale is obtained for the high-temperature metamorphic evolution of the H chondrite parent body. Thermal modeling combined with these age constraints reveals that the different thermal histories of meteorite parent bodies primarily reflect their initial abundance of 26 Al, which is determined by their accretion age. Impact-related processes were important in the subsequent evolution of asteroids but do not appear to have induced large-scale melting. For instance, Hf-W ages for eucrite metals postdate CAI formation by 10Myr.Asimilartimescaleisobtainedforthehigh−temperaturemetamorphicevolutionoftheHchondriteparentbody.Thermalmodelingcombinedwiththeseageconstraintsrevealsthatthedifferentthermalhistoriesofmeteoriteparentbodiesprimarilyreflecttheirinitialabundanceof26Al,whichisdeterminedbytheiraccretionage.Impact−relatedprocesseswereimportantinthesubsequentevolutionofasteroidsbutdonotappeartohaveinducedlarge−scalemelting.Forinstance,Hf−WagesforeucritemetalspostdateCAIformationby20 Myr and may reflect impact-triggered thermal metamorphism in the crust of the eucrite parent body. Likewise, the Hf-W systematics of some non-magmatic iron meteorites were modified by impact-related processes but the timing of this event(s) remains poorly constrained.
Earth’s composition was modified by collisional erosion
Science, 2022
The 146 Sm-142 Nd short-lived decay system (half-life of 103 Ma) is a powerful tracer of the early mantle-crust evolution of planetary bodies. However, an elevated 142 Nd/ 144 Nd in modern terrestrial rocks relative to chondrite meteorites has been proposed to be caused by nucleosynthetic anomalies, obscuring the early Earth's differentiation history. We use step-wise dissolution of primitive chondrites to quantify nucleosynthetic contributions on the composition of chondrites. After correction for nucleosynthetic anomalies, Earth and the silicate parts of differentiated planetesimals contain resolved excesses of 142 Nd relative to chondrites. We conclude that only collisional erosion of primordial crusts can explain such compositions. This process associated with planetary accretion must have produced substantial loss of incompatible elements including long-term heat producing elements such as U, Th, and K.
A hypothesis on the origin of C-type asteroids and carbonaceous chondrites
arXiv (Cornell University), 2012
A hypothesis based on observational and theoretical results about the origin of C-type asteroids and carbonaceous chondrites is put forward. Asteroids of C-type and close BGF-types could form from hydrated silicate-organic matter accumulated in the cores of water-differentiated bodies existed in the growth zone of Jupiter and, possibly, Saturn. The gravitational scattering of such bodies by Jupiter at its final stage of formation to the main asteroid belt might have led to fragmentation and re-accretion of their primitive matter on the surfaces of many asteroids and/or asteroid parent bodies. Similarly, asteroids of other primitive types (D and P) characterized, probably, elevated content of organics could origin from the matter of small bodies accreted and evolved in the growth zones of Uranus and Neptune and then dispersed by the giant planets to the asteroid belt. The hypothesis makes clear a row of long-standing puzzling facts, the main of which are as follows. The low-albedo and carbonaceous-chondritic surface properties of (1) Ceres contradict to its probable differentiated structure and icy crust (e. g.,
Nature Communications
Meso-Cenozoic evidence suggests links between changes in the expression of orbital changes and millennia-scale climatic- and biotic variations, but proof for such shifts in orbital cyclicity farther back in geological time is lacking. Here, we report a 469-million-year-old Palaeozoic energy transfer from precession to 405 kyr eccentricity cycles that coincides with the start of the Great Ordovician Biodiversification Event (GOBE). Based on an early Middle Ordovician astronomically calibrated cyclostratigraphic framework we find this orbital change to succeed the onset of icehouse conditions by 200,000 years, suggesting a climatic origin. Recently, this icehouse was postulated to be facilitated by extra-terrestrial dust associated with an asteroid breakup. Our timescale, however, shows the meteor bombardment to post-date the icehouse by 800,000 years, instead pausing the GOBE 600,000 years after its initiation. Resolving Milankovitch cyclicity in deep time thus suggests universal orb...