Meteorites

Question 1

what is a meteorite?

Answer 1

solid extraterrestrial material that has survived the descent through Earth’s atmosphere

Question 2

what is the difference between a meteorite find and a meteorite fall

Answer 2

a find is when you find a strange metallic object or go on an expedition to Antarctica or a desert to find meteorites

a fall is when the meteorite fireball is observed and the freshly fallen pieces are found on the ground

Question 3

what are the uses of meteorite falls over meteorite finds?

Answer 3

1. chemical/isotopic analyses due to the freshness of the samples (absence of weathering and terrestrial alteration) – don’t know when a meteorite find had fell
2. stats on different meteorite types - no sampling bias i.e. can figure out how numerous different meteorites are as some weather faster than others

Question 4

what is a meteorite parent body?

Answer 4

all meteorites are derived from a parent body, and are disloged from their parent body by impact events, laughing debris into new orbits. many parent bodies from asteroid belt

Question 5

what are the 3 broad classifications of meteorites?

Answer 5

stones, irons and stony-irons

Question 6

what are the 2 types of stony meteorites?

Answer 6

chrondrites and achondrites

Question 7

what are the 3 types of chondrites?

Answer 7

carbonaceous, ordinary and enstatite

Question 8

what type of chondrite is the most common?

Answer 8

ordinary chondrites

Question 9

what are the main constituents of chondrites?

Answer 9

Chondrules
CAIs
Matrix

Question 10

what are chondrules

Answer 10

nearly spherical droplets of mm size formed by rapid heating/melting and subsequent quenching of silicates

Question 11

what are CAIs

Answer 11

calcium aluminium inclusions - white irregularly shaped inclusions rich in refractory elements (CaO, Al2O3) which condensed very early in the solar system

Question 12

how are different chondrites classified?

Answer 12

they are grouped:
1. into different letters e.g. CI, H, L
2. based on petrological type (amount of aqueous or thermal metamorphism)

Question 13

what is a petrological type of 3 in a chondrite

Answer 13

an ‘unequilibriated’ chondrite which has experienced the least/no thermal or aqueous metamorphism (secondary processes)

Question 14

which chondrites have the highest volatile content?

Answer 14

carbonaceous chondrites

Question 15

what type of meteorite are used to define the average composition of the solar system?

Answer 15

CI carbonaceous chondrites?

Question 16

why is it good that CI carbonaceous chondrites are primitive i.e. formed early and have not been affected by heating, core formation or igneous processes?

Answer 16

they provide an early chemical composition of the solar system

Question 17

what does the onion-shell model state?

Answer 17

for the ordinary and enstatite chondrites, their different petrological types correspond to the depth of burial on the meteorite parent body, with the unequilibrated type 3 samples derided from the surface. equilibrated types 4 5 and 6 are derived from increasing depths of the parent body (increasing thermal metamorphosis) ~950C

Question 18

what are achondrites?

Answer 18

silicate-rich mafic, ultramafic partial-melt derived igneous meteorites from the mantle of differentiated asteroids or planets.

Question 19

what are iron meteorites?

Answer 19

Fe-Ni metal with some FeS inclusions, most of which are remnants of asteroid cores.

Question 20

what are stony-irons?

Answer 20

Fe-Ni metal plus silicate. includes mesosiderites and pallasites (olivine+metal)

they are thought to represent the core mantle boundary of differentiated asteroids.