EAS206 Lecture Notes - Lecture 14: Allan Hills 84001, Igneous Rock, Breccia
30 Apr 2018
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• Mars can be a challenging place to explore
• Martian meteorites
o SNCs
• How do we kow they’re fro Mars?
o Viking landers analysed the Martian atmosphere
▪ Martian atmosphere is unique out of the whole solar system
o Strongest piece of evidence: the presence of trapped Martian atmosphere
o Pockets of glass in which atmosphere gas is trapped (black stuff on basalt gray
rock pic)
• Just for one ratio (gases in meteorite = gases in Martian atmosphere)
• Oxygen isotopes
o All the samples fall on the same line so we know they’re from the same place
• Martian igneous rocks
o Have some young volcanoes
o Veins
▪ Impact shock from the impact on the surface of Mars
▪ Impactor hits Mars, can cause enough velocity of the debris to escape the
orbit of Mars
o 80% shergottites*** (need to know!!)
o NWA = more of a breccia, not really an igneous rock
o Bias towards rocks that are younger
o Basalts
▪ Tissint
• Fusion crust = outside heats up to become molten but is a thin
layer
• Black glass = shock melt glass
o Has gases from Martian atmosphere
o Clinopyroxenites (relative age?)
▪ Mostly Ca-pyroxene
o Dunites
▪ Mostly olivine
o Orthopyroxenites
▪ Water percolating through the rock
▪ ALH 84001
o Balsatic breccia
▪ Do’t need to know about lapilli
▪ First sample of sedimentary rock of the Martian meteorites
o Augite-rich shergottites
o Gives us info on igneous processes, etc.
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