Question

5.a. What class of meteorite should have a composition closest to cosmic abundances? Why?

5.b. Most asteroids are C-type, but most meteorites are not carbonaceous chondrites. Why might this be?

5.c. Consider three types of meteorites: irons, carbonaceous chondrites, and enstatite
chondrites. What are likely condensation temperatures for these meteorites? Near which
planets would these temperatures be found?

Answer 1

5. a) Carbonaceous chondrites have a composition closest to cosmic abundances. This can be attributed to the fact that they are made up of low temperature condensates that escaped the harsh processes that other meteorites couldn't. They are also the most primitive of all as they they still contain volatile material. Their composition is very similar to the Sun.

5. b) Many of the C-type asteroids reached high enough temperatures that resulted in internal thermal metamorphism. All C-type asteroids undergo collisions with other asteroids which causes simple compactions, brecciation, veining, localized melting, and formation of high-pressure minerals. These processes leads to only a few C-type asteroids preserved in their original pure form and hence only those which do are known to us as Carbonaceous chondrites meteorites.

5. c) Carbonaceous chondrites meteorites have the highest proportion of volatile compounds and hence have been formed the farthest from the sun, in the cooler outer portion of the solar nebula. It is thought they have not been heated above 50 °C.

enstatite chondrites were formed in an area that lacked oxygen, probably within the orbit of Mercury as they are chemically reduced rocks, with most of their iron taking the form of metal or sulfide rather than as an oxide. The temperature at this region is 800 ° F hence it is likely to be it's condensation temperature.

Iron meteorites originate from cores of planetesimals. their condensation temperatures at the time of formation is 600–670 K