Meteorites Flashcards
Where are the best places to collect meteorites on earth?
Antarctic meteorite collection - meteorite falls, wind and glacial ice migrates to a collection surface with its path blocked by a ridge
What is the basic historical classification of meteorites and what type of parent body?
Irons - Type M
Stoney Irons (Iron matrix containing olivine crystals) - Type S
Stones - most common falls and finds
What are the sub-classifications of stoney meteorites and describe them?
Chondrite - melted & recrystallised solar nebula - similar composition to earths mantle. These contain chondrules which are the melted & recrystallised droplets of solar nebular
Carbonaceous chondrite - similar composition to the sun. Closest analogue to primitive solar nebula. Parent body type C being composed of around 15% C and rich in volatiles
Achondrites - the parent body is other planets e.g. Basalts from the Moon
3 Main components of carbonaceous chondrites
CAIs - form close to the sun by evaporation and condensation. They are Ca-Al rich inclusions that have been re-distributed into a cooler region of the solar system by X-wind
Chondrules - melting and recrystallisation of solar dust
Fine matrix - origin uncertain as has such an extreme isotope composition
Why are oxygen isotope classifications useful?
16O, 17O &18O produced by stellar nucleosynthesis
16O is the primary isotope created from H and He done in red giants
17O & 18O are secondary nuclei forming earlier in generations of stars
Meteorites and planets all have different 16O, 17O & 18O (recipes) as they were made in different parts of the solar system
How processed are comets, meteorites, asteroids, planets and the sum from solar nebula?
Comets - least processed
Meteorites & asteroids - partly processed
Planets & The Sun - processed
What are igneous meteorites and what type of meteors are classified as these?
Achondrites (planets), Irons (Solar nebula melt) & Stoney Iron
Formed from asteroids that did melt to form metallic cores & silicate mantle meaning they are differentiated
Iron - core
Stoney iron - core/mantle
Achondrite - mantle
What are SNCs and what is the evidence of a mars origin?
SNC Meteorites evolved in a similar way to planetary bodies e.g. Mars, Earth etc.
Evidence for mars origin
SPALLATION AGE (time of flight in space is low) therefore, the parent body must be intact
All known have low CRYSTALLISATION AGE therefore source is a planet
MAJOR ELEMENT COMPOSITION different to terrestrial rocks
Distinct O ISOTOPE (known pattern from moon and earth)
Preferred igneous source (mercury to small for volcanoes)
Presence of TRAPPED METHANE atmosphere - similar to that of VIKING lander analysis
How do we date meteorites?
Conventional dating (U-Pb, Pb-Pb) has a very long half life older than the solar system
Therefore we need to identify shorter half lives ones less than 20My e.g. 26Al-26Mg (780,000y) as this was an abundant element in rocks this will be good for ageing
Neutron activated very early in the solar system due to nearby supernova that triggered collapse of the solar nebula
These isotopes are ow extinct but there activity can be detected by DAUGHTER ISOTOPES. Dating is relative to the start of the formation of the solar system
