Extraterrestrial phenomena have influenced Earth’s processes throughout geological history.Evaluating the impact of extraterrestrial material on the environment is crucial for understanding the evolution of Earth and...Extraterrestrial phenomena have influenced Earth’s processes throughout geological history.Evaluating the impact of extraterrestrial material on the environment is crucial for understanding the evolution of Earth and life.This study incorporates the investigation of micrometeorites(MMs),abundant cosmic materials on Earth,to understand their influence on the chemical composition and biogeochemistry of the ocean.Comprehensive etching and flux analyses reveal that∼95%of cosmic spherules(CSs)entering seawater are etched or wholly dissolved,supplying nutrients to phytoplankton.Barred spherules show the highest degree of etching(∼19%),followed by porphyritic(∼17%),glass(∼15%),cryptocrystalline(∼12%),scoriaceous(∼10%),G-type(∼9%),and I-type(∼6%).Annually,∼3080 tonnes(t)of olivine from MMs dissolve into seawater,contributing∼495 t of Mg^(2+),∼1110 t of Fe^(2+),and∼1928 t of silicic acid.This signifies that over the Indian Ocean’s∼40 Myr history,∼23 Gt of olivine from CSs has dissolved,providing nutrients to seawater and sequestering∼7 Gt of CO_(2).The world ocean during this time has sequestered∼35 Gt of CO_(2),with fluctuations influenced by extraterrestrial activity.For instance,the Veritas event,lasting∼1.5 Myr,sequestered∼6 Gt of CO_(2)from the atmosphere.A robust flux calculation based on∼2 t of deep-sea sediments from 3610 MMs provides a more accurate estimate of the time-averaged flux of∼229 t yr^(−1).These comprehensive analyses reveal MM’s original characteristics,post-deposition processes,geological record and their overall impact on Earth’s marine environments,thereby contributing to our knowledge of the interconnection between terrestrial and extraterrestrial processes.展开更多
Extraterrestrial dust exhibits a wide range of textural,chemical and oxygen isotopic compositions due to the heterogeneity of their precursors and modification during atmospheric entry.Experimental heating provides an...Extraterrestrial dust exhibits a wide range of textural,chemical and oxygen isotopic compositions due to the heterogeneity of their precursors and modification during atmospheric entry.Experimental heating provides an opportunity to investigate the relationship between thermal processing and micrometeorite composition for a known precursor material.We conducted experiments to simulate the atmospheric entry of micrometeorites(MMs)using controlled,short-duration(10-50 s)flash heating(400-1600℃)of CI chondrite chips(<1500µm)in atmospheric air(1 bar,21%O2)combined with microanalysis(textures,chemical and isotopic compositions)of the experimental products.The heated chips closely resemble natural samples,with materials similar to unmelted MMs,partially melted(scoriaceous)MMs and fully melted cosmic spherules produced.We reproduced several key features such as dehydration cracks,magnetite rims,volatile gas release,vesicle formation and coalescence,melting and quench cooling.Our parameter space allows for discriminating peak temperature and heating duration effects.Peak temperature is the first-order control on MM mineralogy,while heating duration controls vesicle coalescence and homogenization.When compared against previous heating experiments,our data demonstrates that CI chondrite dust is more thermally resistant,relative to CM chondrite dust,by approximately+200℃.The 207 measurement of O-isotopes allows,for the first time,petrographic effects(such as volatile degassing and melting)to be correlated against bulk O-isotope evolution.Our results demonstrate findings applicable to CI chondrites and potentially to all fine-grained hydrated carbonaceous chondrite dust grains:(1)O-isotope variations arising during sub-solidus heating are dominated by the release of water from phyllosilicates,forcing the residual MM composition towards its anhydrous precursor composition.(2)Oxygen isotope compositions undergo the most significant changes at supra-solidus temperatures.As previously demonstrated and now empirically confirmed,most of these changes are driven by a mass-dependent fractionation effect caused by evaporation,which shifts residual rock compositions toward heavier values.Mixing with atmospheric air alters compositions toward the terrestrial fractionation line.Notably,these two processes do not begin simultaneously.Our data indicate that at 1200℃,isotopic evolution is dominated by evaporative mass loss.However,at higher temperatures(1400-1600℃),both pronounced evaporation and mixing with atmospheric oxygen become active,resulting in a more complex isotopic signature.(3)The total change in Δ17O during heating up to 1600℃is<3‰and in most scenarios<2‰.展开更多
The carbonaceous chondrites are intriguing and unique in the sense that they are the only rocks that provide pristine records of the early solar nebular processes. We report here results of a detailed mineralogical, c...The carbonaceous chondrites are intriguing and unique in the sense that they are the only rocks that provide pristine records of the early solar nebular processes. We report here results of a detailed mineralogical, chemical, amino acid and isotopic studies of a recently observed fall at Mukundpura, near Jaipur in Rajasthan, India. Abundance of olivines in this meteorite is low and of serpentine minerals is high. FeO/SiO_2 = 1.05 in its Poorly Characterized Phases(PCP) is similar to that observed in other CM2.0 chondrites. The water content of ～9.8 wt.% is similar to that found in many other CM chondrites.Microscopic examination of matrix shows that its terrestrial weathering grade is WO but aqueous parent body alteration is high, as reflected in low abundance of identifiable chondrules and abundant remnants of chondrules(～7%). Thus, most of the chondrules formed initially have been significantly altered or dissolved by aqueous alterations on their parent bodies. The measured bulk carbon(2.3%) and nitrogen content and their isotopic(δ^(13)C =-5.5‰, δ^(15)N = 23.6%0) composition is consistent with CM2.0 classification probably bordering CM1. Several amino acids such as Alanine, Serine, Proline, Valine, Threonine,Leucine, Isoleucine, Asparagine and Histamine are present. Tyrosine and Tryptophan may occur in trace amounts which could not be precisely determined. All these data show that Mukundpura chondrite lies at the boundary of CM2.0 and CM1 type carbonaceous chondrites making it one of the most primitive chondrites.展开更多
We report unearthing the first silicate-type(S-type)lunar Antarctic micrometeorites(AMM)spherule and another spherule with a refractory chondritic phase.The lunar spherule is made of Augite with minor Ni magnetite(<...We report unearthing the first silicate-type(S-type)lunar Antarctic micrometeorites(AMM)spherule and another spherule with a refractory chondritic phase.The lunar spherule is made of Augite with minor Ni magnetite(<1 wt.%),in contrast to other known cosmic spherules.The Augite’s minor oxide range in the spherule are as follows:Wo_(37-41)En_(25-27)Fs_(34-36),Al_(2)O_(3):0.7–1 wt.%,Cr_(2)O_(3):0.01–0.06 wt.%,MnO:0.32–0.39 wt.%and TiO_(2):0.03–0.09 wt.%.The lunar spherule’s chemical characteristics indicate that it originated from very low Ti lunar basalt(VLT)mare basalts.Chondritic diopside(Wo_(46-47)En_(50-47)Fs_(5-6),Al_(2)O_(3):1.7–1.6 wt.%,Cr_(2)O_(3):0.6–0.63 wt.%,MnO:0.2–0.4 wt.%,and TiO_(2):0.0–0.02 wt.%)makes up the refractory phase in the second spherule.The chemical composition of diopside is indistinct from those of calcium aluminium inclusion(CAIs)found in both ordinary and carbonaceous chondrites.Our finding reveals that micron-sized lunar impact debris can potentially reach the Earth’s surface,similar to the earliest formed nebulae solid component.展开更多
基金ISRO-RESPOND GAP3332 and PMN-MOES GAP2175 Project support this work.NIO-PMN and MOES-NCPOR supported the deep-sea and Antarctica micrometeorite collections,respectively.
文摘Extraterrestrial phenomena have influenced Earth’s processes throughout geological history.Evaluating the impact of extraterrestrial material on the environment is crucial for understanding the evolution of Earth and life.This study incorporates the investigation of micrometeorites(MMs),abundant cosmic materials on Earth,to understand their influence on the chemical composition and biogeochemistry of the ocean.Comprehensive etching and flux analyses reveal that∼95%of cosmic spherules(CSs)entering seawater are etched or wholly dissolved,supplying nutrients to phytoplankton.Barred spherules show the highest degree of etching(∼19%),followed by porphyritic(∼17%),glass(∼15%),cryptocrystalline(∼12%),scoriaceous(∼10%),G-type(∼9%),and I-type(∼6%).Annually,∼3080 tonnes(t)of olivine from MMs dissolve into seawater,contributing∼495 t of Mg^(2+),∼1110 t of Fe^(2+),and∼1928 t of silicic acid.This signifies that over the Indian Ocean’s∼40 Myr history,∼23 Gt of olivine from CSs has dissolved,providing nutrients to seawater and sequestering∼7 Gt of CO_(2).The world ocean during this time has sequestered∼35 Gt of CO_(2),with fluctuations influenced by extraterrestrial activity.For instance,the Veritas event,lasting∼1.5 Myr,sequestered∼6 Gt of CO_(2)from the atmosphere.A robust flux calculation based on∼2 t of deep-sea sediments from 3610 MMs provides a more accurate estimate of the time-averaged flux of∼229 t yr^(−1).These comprehensive analyses reveal MM’s original characteristics,post-deposition processes,geological record and their overall impact on Earth’s marine environments,thereby contributing to our knowledge of the interconnection between terrestrial and extraterrestrial processes.
基金ISRO-RESPOND GAP3332 and PMN-MOES GAP2175 Project support this work.
文摘Extraterrestrial dust exhibits a wide range of textural,chemical and oxygen isotopic compositions due to the heterogeneity of their precursors and modification during atmospheric entry.Experimental heating provides an opportunity to investigate the relationship between thermal processing and micrometeorite composition for a known precursor material.We conducted experiments to simulate the atmospheric entry of micrometeorites(MMs)using controlled,short-duration(10-50 s)flash heating(400-1600℃)of CI chondrite chips(<1500µm)in atmospheric air(1 bar,21%O2)combined with microanalysis(textures,chemical and isotopic compositions)of the experimental products.The heated chips closely resemble natural samples,with materials similar to unmelted MMs,partially melted(scoriaceous)MMs and fully melted cosmic spherules produced.We reproduced several key features such as dehydration cracks,magnetite rims,volatile gas release,vesicle formation and coalescence,melting and quench cooling.Our parameter space allows for discriminating peak temperature and heating duration effects.Peak temperature is the first-order control on MM mineralogy,while heating duration controls vesicle coalescence and homogenization.When compared against previous heating experiments,our data demonstrates that CI chondrite dust is more thermally resistant,relative to CM chondrite dust,by approximately+200℃.The 207 measurement of O-isotopes allows,for the first time,petrographic effects(such as volatile degassing and melting)to be correlated against bulk O-isotope evolution.Our results demonstrate findings applicable to CI chondrites and potentially to all fine-grained hydrated carbonaceous chondrite dust grains:(1)O-isotope variations arising during sub-solidus heating are dominated by the release of water from phyllosilicates,forcing the residual MM composition towards its anhydrous precursor composition.(2)Oxygen isotope compositions undergo the most significant changes at supra-solidus temperatures.As previously demonstrated and now empirically confirmed,most of these changes are driven by a mass-dependent fractionation effect caused by evaporation,which shifts residual rock compositions toward heavier values.Mixing with atmospheric air alters compositions toward the terrestrial fractionation line.Notably,these two processes do not begin simultaneously.Our data indicate that at 1200℃,isotopic evolution is dominated by evaporative mass loss.However,at higher temperatures(1400-1600℃),both pronounced evaporation and mixing with atmospheric oxygen become active,resulting in a more complex isotopic signature.(3)The total change in Δ17O during heating up to 1600℃is<3‰and in most scenarios<2‰.
基金carried out with the support of MOES-PMN and PLANEX (Physical Research Laboratory, Ahmedabad) programs
文摘The carbonaceous chondrites are intriguing and unique in the sense that they are the only rocks that provide pristine records of the early solar nebular processes. We report here results of a detailed mineralogical, chemical, amino acid and isotopic studies of a recently observed fall at Mukundpura, near Jaipur in Rajasthan, India. Abundance of olivines in this meteorite is low and of serpentine minerals is high. FeO/SiO_2 = 1.05 in its Poorly Characterized Phases(PCP) is similar to that observed in other CM2.0 chondrites. The water content of ～9.8 wt.% is similar to that found in many other CM chondrites.Microscopic examination of matrix shows that its terrestrial weathering grade is WO but aqueous parent body alteration is high, as reflected in low abundance of identifiable chondrules and abundant remnants of chondrules(～7%). Thus, most of the chondrules formed initially have been significantly altered or dissolved by aqueous alterations on their parent bodies. The measured bulk carbon(2.3%) and nitrogen content and their isotopic(δ^(13)C =-5.5‰, δ^(15)N = 23.6%0) composition is consistent with CM2.0 classification probably bordering CM1. Several amino acids such as Alanine, Serine, Proline, Valine, Threonine,Leucine, Isoleucine, Asparagine and Histamine are present. Tyrosine and Tryptophan may occur in trace amounts which could not be precisely determined. All these data show that Mukundpura chondrite lies at the boundary of CM2.0 and CM1 type carbonaceous chondrites making it one of the most primitive chondrites.
基金The GEOSINKS,PMN-Ministry of Earth Sciences,and the ISRO-Respond project support this workthe UGC-Council of Scientific and Industrial Research for financial support.This is NIO’s contribution no.7330.
文摘We report unearthing the first silicate-type(S-type)lunar Antarctic micrometeorites(AMM)spherule and another spherule with a refractory chondritic phase.The lunar spherule is made of Augite with minor Ni magnetite(<1 wt.%),in contrast to other known cosmic spherules.The Augite’s minor oxide range in the spherule are as follows:Wo_(37-41)En_(25-27)Fs_(34-36),Al_(2)O_(3):0.7–1 wt.%,Cr_(2)O_(3):0.01–0.06 wt.%,MnO:0.32–0.39 wt.%and TiO_(2):0.03–0.09 wt.%.The lunar spherule’s chemical characteristics indicate that it originated from very low Ti lunar basalt(VLT)mare basalts.Chondritic diopside(Wo_(46-47)En_(50-47)Fs_(5-6),Al_(2)O_(3):1.7–1.6 wt.%,Cr_(2)O_(3):0.6–0.63 wt.%,MnO:0.2–0.4 wt.%,and TiO_(2):0.0–0.02 wt.%)makes up the refractory phase in the second spherule.The chemical composition of diopside is indistinct from those of calcium aluminium inclusion(CAIs)found in both ordinary and carbonaceous chondrites.Our finding reveals that micron-sized lunar impact debris can potentially reach the Earth’s surface,similar to the earliest formed nebulae solid component.
