Nucleosynthetic
processes:
Fusion:
•Hydrogen
•Helium
•Carbon
•Oxygen
After Fe, neutron addition
takes place (rapid and
slow processes)
Summary – Solar abundances of the elements:
• H and He are the most abundant elements
• Elements with higher atomic numbers decrease in
abundance exponentially
• Peak at Fe, unusually low abundances for Li, Be, B
• Isotopes with even atomic numbers and mass numbers
more abundant than those with odd atomic numbers
• Sun is H-burning to form He, solar system contains
elements formed in older, more massive stars
Meteorites – extraterrestrial rocks that enter the Earth’s
atmosphere and strike the Earth’s surface
Basic Classification:
• Stony (silicates)
– Chondrites
– Achondrites
• Stony-iron (mixed silicate and metal)
• Iron (metal)
Falls are witnessed falling through the atmosphere (meteors),
finds are found. Most finds are irons.
http://meteorites.asu.edu/
The nebular
hypothesis
The solar nebula
(gas) contracted,
cooled and
condensed into
dust sized particles
that accreted (stuck
together as the
result of collisions)
into protoplanets
(asteroid sized
bodies) and then
larger planets
http://meteorites.asu.edu/
Evidence that chondrites are representative of
early solar system materials:
• 1:1 ratio of non-volatile elements to those in the sun
• “sedimentary”, non-equilibrated texture - formed by
accretion of condensed particles with little subsequent
heating or alteration
• presence of minerals predicted to be formed by
condensation of solar nebula, such as corundum, Fe
metal, troilite, etc.
Also inferred: achondrites, iron and stony-meteorites
represent fragments of accreted planetesimals that had
heated internally, melted and differentiated
The nebular
hypothesis
The solar nebula
(gas) contracted,
cooled and
condensed into
dust sized particles
that accreted (stuck
together as the
result of collisions)
into protoplanets
(asteroid sized
bodies) and then
larger planets
Measured
quantity =
Heat of
vaporization
Hypotheses for the formation of Earth (other
planets and moons)
• Heterogeneous accretion
• Homogeneous accretion
• Chondrite mixing
Chondrite minerals:
•Ca-Al inclusions (CAI’s)
(corundum, perovskite,
melilite, anorthite)
•Silicates in chondrules:
enstatite, diopside, olivine,
anorthite
•Metal: Fe, Ni
•Troilite (FeS)
•Serpentine
•Carbonaceous material