Ib lub meteorite yog lub cev muaj zog ntawm lub ntiaj teb cosmic keeb kwm uas tau poob rau saum npoo ntawm lub ntiaj teb, nrog qhov loj ntawm 2 hli lossis ntau dua. Lub cev uas tau mus txog saum npoo ntawm lub ntiaj teb thiab muaj qhov ntau thiab tsawg ntawm 10 microns mus rau 2 hli feem ntau hu ua micrometeorites; cov me me yog cov hmoov av cosmic. Meteorites yog tus cwj pwm los ntawm kev sib txawv thiab cov qauv. Cov yam ntxwv no qhia txog cov xwm txheej ntawm lawv lub hauv paus chiv keeb thiab tso cai rau cov kws tshawb fawb los txiav txim siab txog kev hloov pauv ntawm lub cev ntawm lub hnub ci.
Hom meteorites los ntawm cov tshuaj muaj pes tsawg leeg thiab cov qauv
Meteoritic teeb meem feem ntau yog tsim los ntawm cov ntxhia thiab hlau hauv ntau qhov sib npaug. Cov pob zeb hauv av yog hlau-magnesium silicates, cov hlau yog sawv cev los ntawm nickel hlau. Qee qhov meteorites muaj impurities uas txiav txim siab qee qhov tseem ceeb thiab nqa cov ntaub ntawv hais txog keeb kwm ntawm lub hnub qub.
Meteorites faib los ntawm cov tshuaj lom neeg li cas? Kev lig kev cai, muaj peb pawg loj:
- Pob zeb meteorites yog lub cev silicate. Ntawm lawv yog chondrites thiab achondrites, uas muaj qhov sib txawv ntawm cov txheej txheem tseem ceeb. Yog li, chondrites yog tus cwj pwm los ntawm qhov muaj kev sib koom ua ke - chondrules - hauv cov ntxhia matrix.
- Hlau meteorites,muaj feem ntau ntawm nickel hlau.
- Ironstone - lub cev ntawm cov qauv nruab nrab.
Ntxiv rau qhov kev faib tawm, uas coj mus rau hauv tus account cov tshuaj muaj pes tsawg leeg ntawm cov meteorites, kuj tseem muaj lub hauv paus ntsiab lus ntawm kev faib "cov pob zeb saum ntuj ceeb tsheej" ua ob pawg dav raws li cov qauv nta:
- differentiated, uas suav nrog tsuas yog chondrites;
- undifferentiated - ib pab pawg dav uas suav nrog txhua hom meteorites.
Chondrites yog qhov seem ntawm lub protoplanetary disk
Ib qho tshwj xeeb ntawm hom meteorites no yog chondrules. Lawv feem ntau yog silicate formations ntawm ib tug elliptical los yog kheej kheej, txog 1 hli nyob rau hauv loj. Lub hauv paus muaj pes tsawg leeg ntawm chondrites yuav luag zoo ib yam rau cov muaj pes tsawg leeg ntawm lub hnub (yog tias peb tsis suav cov feem ntau volatile, lub teeb ntsiab - hydrogen thiab helium). Raws li qhov tseeb no, cov kws tshawb fawb tau los txiav txim siab tias chondrites tau tsim thaum kaj ntug ntawm lub hnub ci muaj nyob ncaj qha los ntawm huab cua protoplanetary.
Cov meteorites no yeej tsis tau ua ib feem ntawm lub cev xilethi-aus loj uas twb dhau los ua qhov sib txawv ntawm magmatic. Chondrites tau tsim los ntawm condensation thiab acretion ntawm protoplanetary teeb meem, thaum muaj ib co thermal teebmeem. Cov khoom ntawm chondrites yog tuab heev - los ntawm 2.0 mus rau 3.7 g / cm3 - tab sis tsis yooj yim: lub meteorite tuaj yeem tsoo los ntawm tes.
Cia peb saib kom ze rau qhov muaj pes tsawg leeg ntawm meteorites ntawm hom no, feem ntau (85.7%) ntawm tag nrho.
YCarbonaceous chondrites
Rau carbonaceouschondrites (C-chondrites) muaj cov ntsiab lus siab ntawm cov hlau hauv silicates. Lawv cov xim tsaus yog vim muaj cov hlau nplaum, nrog rau cov impurities xws li graphite, soot thiab organic compounds. Tsis tas li ntawd, carbonaceous chondrites muaj dej khi rau hauv hydrosilicates (chlorite, serpentine).
Raws li ntau tus yam ntxwv, C-chondrites tau muab faib ua ntau pawg, ib qho ntawm - CI-chondrites - yog qhov tshwj xeeb rau cov kws tshawb fawb. Cov cev no tshwj xeeb uas lawv tsis muaj chondrules. Nws yog assumed tias cov khoom ntawm meteorites ntawm pab pawg no tsis raug thermal cuam tshuam rau tag nrho, uas yog, nws tseem xyaum tsis hloov txij li lub sij hawm ntawm condensation ntawm lub protoplanetary huab. Cov no yog lub cev qub tshaj plaws hauv lub hnub ci.
Organics hauv meteorites
Carbonaceous chondrites muaj xws li cov organic tebchaw xws li aromatic thiab saturated hydrocarbons, nrog rau carboxylic acids, nitrogenous bases (nyob rau hauv cov kab mob nyob lawv yog ib feem ntawm nucleic acids) thiab porphyrins. Txawm hais tias qhov kub thiab txias tau dhau los ntawm lub meteorite thaum nws dhau los ntawm lub ntiaj teb huab cua, hydrocarbons tau khaws cia los ntawm kev tsim cov pob zeb yaj uas ua rau cov cua sov zoo.
Cov tshuaj no, feem ntau yuav, yog keeb kwm abiogenic thiab qhia txog cov txheej txheem ntawm thawj cov organic synthesis twb nyob rau hauv cov xwm txheej ntawm huab cua protoplanetary, muab lub hnub nyoog ntawm carbonaceous chondrites. Yog li ntawd lub ntiaj teb cov tub ntxhais hluas twb nyob rau theem ntxov tshaj plaws ntawm nws lub neej muaj cov khoom siv rau kev tshwm sim ntawm lub neej.
Nyob zoo thiabEnstatite chondrites
Feem ntau yog cov chondrites zoo tib yam (li no lawv lub npe). Cov meteorites no muaj, ntxiv rau silicates, npib tsib xee hlau thiab dais kab ntawm thermal metamorphism ntawm qhov kub ntawm 400-950 ° C thiab poob siab txog li 1000 atmospheres. Cov chondrules ntawm lub cev no feem ntau tsis sib xws; lawv muaj cov khoom detrital. Ordinary chondrites suav nrog, piv txwv li, Chelyabinsk meteorite.
Enstatite chondrites yog tus cwj pwm los ntawm qhov tseeb tias lawv muaj cov hlau feem ntau hauv daim ntawv hlau, thiab cov khoom siv silicate yog nplua nuj nyob hauv magnesium (enstatite ntxhia). Cov pab pawg no ntawm cov meteorites muaj cov tshuaj tsis haum tsawg dua li lwm cov chondrites. Lawv underwent thermal metamorphism ntawm qhov kub ntawm 600-1000 ° C.
Meteorites uas yog ob pawg ntawm pawg no feem ntau yog cov tawg ntawm asteroids, uas yog, lawv yog ib feem ntawm cov me me protoplanetary lub cev uas cov txheej txheem ntawm subsurface sib txawv tsis tshwm sim.
Differentiated meteorites
Tam sim no cia peb tig los saib seb hom meteorites txawv ntawm cov tshuaj muaj pes tsawg leeg hauv pawg loj no.
Ua ntej, cov no yog pob zeb achondrites, thib ob, hlau-pob zeb thiab, thib peb, hlau meteorites. Lawv koom siab los ntawm qhov tseeb tias txhua tus neeg sawv cev ntawm pawg tau teev tseg yog cov khoom tawg ntawm lub cev loj ntawm lub hnub qub lossis lub ntiaj teb loj, sab hauv uas tau dhau los ua qhov sib txawv ntawm qhov teeb meem.
Ntawm cov meteorites sib txawv yog pom lifragments ntawm asteroids, thiab lub cev khob tawm ntawm lub hli los yog Mars.
Ntawm cov meteorites sib txawv
Achondrite tsis muaj qhov tshwj xeeb suav nrog thiab, ua cov hlau tsis zoo, yog silicate meteorite. Nyob rau hauv muaj pes tsawg leeg thiab cov qauv, achondrites nyob ze rau av thiab lunar bas alts. Qhov kev txaus siab zoo yog HED pab pawg meteorites, xav tias yog los ntawm lub mantle ntawm Vesta, uas xav tias yog ib qho chaw khaws cia hauv av. Lawv zoo ib yam li cov pob zeb ultramafic ntawm lub ntiaj teb sab saum toj mantle.
Stony-hlau meteorites - pallasite thiab mesosiderite - yog tus cwj pwm los ntawm kev muaj cov silicate suav nrog hauv nickel-hlau matrix. Pallasites tau txais lawv lub npe nyob rau hauv kev hwm ntawm nto moo Pallas hlau pom nyob ze Krasnoyarsk nyob rau hauv lub xyoo pua 18th.
Ib feem ntau cov meteorites hlau muaj cov qauv nthuav - "widmanstetten cov duab", tsim los ntawm cov hlau npib tsib xee nrog cov ntsiab lus nickel sib txawv. Cov qauv no tau tsim nyob rau hauv cov xwm txheej ntawm qeeb crystallization ntawm nickel hlau.
Keeb kwm ntawm "cov pob zeb saum ntuj ceeb tsheej"
Chondrites yog cov xa xov los ntawm lub sijhawm qub tshaj plaws ntawm kev tsim lub hnub ci - lub sijhawm sib sau ntawm cov teeb meem pre-planetary thiab yug ntawm planetesimals - embryos ntawm lub ntiaj teb yav tom ntej. Radioisotope yos ntawm chondrites qhia tau hais tias lawv lub hnub nyoog tshaj 4.5 billion xyoo.
Raws li cov meteorites sib txawv, lawv qhia peb txog kev tsim cov qauv ntawm lub cev ntawm lub ntiaj teb. LawvCov khoom muaj cov cim qhia ntawm melting thiab recrystallization. Lawv txoj kev tsim tuaj yeem tshwm sim nyob rau hauv ntau qhov chaw ntawm niam txiv lub cev sib txawv, uas tom qab ntawd ua tiav los yog kev puas tsuaj ib nrab. Qhov no txiav txim siab seb cov tshuaj muaj pes tsawg leeg ntawm cov meteorites, cov qauv tsim nyob rau hauv txhua rooj plaub, thiab ua lub hauv paus rau lawv cov kev faib tawm.
Differentiated celestial qhua kuj muaj cov ntaub ntawv hais txog cov kab ke ntawm cov txheej txheem uas tau tshwm sim hauv lub plab ntawm niam txiv lub cev. Xws li, piv txwv li, yog hlau-pob zeb meteorites. Lawv muaj pes tsawg leeg ua tim khawv rau qhov sib cais tsis tiav ntawm lub teeb silicate thiab hnyav hlau Cheebtsam ntawm ancient protoplanet.
Nyob rau hauv cov txheej txheem ntawm kev sib tsoo thiab tawg ntawm asteroids ntawm ntau hom thiab muaj hnub nyoog, cov txheej txheej saum npoo ntawm ntau ntawm lawv tuaj yeem sib xyaw ua ke ntawm ntau lub hauv paus. Tom qab ntawd, raws li qhov tshwm sim ntawm kev sib tsoo tshiab, ib qho zoo sib xws "composite" tawg tau tawm ntawm qhov chaw. Ib qho piv txwv yog Kaidun meteorite uas muaj cov khoom ntawm ntau hom chondrites thiab hlau hlau. Yog li keeb kwm ntawm cov teeb meem meteoritic feem ntau nyuaj thiab tsis meej pem.
Tam sim no, ntau qhov kev saib xyuas tau them rau kev kawm ntawm asteroids thiab ntiaj chaw nrog kev pab los ntawm cov chaw nres tsheb tsis siv neeg interplanetary. Tau kawg, nws yuav ua rau muaj kev tshawb pom tshiab thiab nkag siab tob txog lub hauv paus chiv keeb thiab kev hloov pauv ntawm cov pov thawj zoo li no rau keeb kwm ntawm lub hnub ci system (thiab peb lub ntiaj teb ib yam) raws li meteorites.
