2018 Fall Meeting

10-15 December

Over 200 meteorites from Mars have been collected on Earth.  These igneous rocks record formation conditions on Mars, but are altered in the process of moving between planets.  Most are collected from the deserts of Africa or Antarctica.  Terrestrial contamination makes sample analysis challenging.  These meteorites have unique chemical compositions, with distinctive mineral ratios compared to terrestrial basalts.  The Elephant Moraine (EET) 79001 meteorite, with internal trapped gas, was confirmed to be martian in 1983 by comparison to the measured atmospheric values from NASA’s Viking lander.  The martian meteorites are grouped in three broad categories: Shergottite, Nakhlite, or Chassignite (SNC).  A few don’t fit in the SNC grouping.  The Allan Hills (ALH) 84001, which was incorrectly reported in 1996 to contain fossilized evidence of past martian life, is the oldest martian meteorite at 4.5 Ga (billion years). 

The Nakhlite group is speculated to originate from a single impact on Mars (possibly the Tharsis region) 11 million years ago.  These meteorites represent different formation depths in martian lava at 1.3 Ga.  Subsequently, subsurface brines percolated through the rock and deposited small carbonate crystals.  Analysis of carbonate stable isotope values provides insights into the water and atmosphere values from Mar’s ancient past.

• EP - Earth and Planetary Surface Processes
• P - Planetary Sciences
• V - Volcanology, Geochemistry and Petrology