SNC meteorites

SNC meteorites

A small group of stony (achondrite) meteorites, named after its three main members Shergotty, Nakhla, and Chassigny. These igneous rocks seem to be only 1300 to 200 million years old. It is suggested that they have been ejected from Mars by some crater-producing event.
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Although NWA 7034 has similarities to the SNC meteorites, including the presence of macromolecular organic carbon, this new meteorite has many unique characteristics.
The texture of the NWA meteorite is not like any of the SNC meteorites," co-author Andrew Steele said.
The SNC meteorites, the letters standing for the names of the three most prominent of the group (Shergotty, Nakhla, and Chassigny), were unlike almost any other.
Finally, there came a breakthrough; a SNC meteorite was recovered in Antarctica that partially had been melted when it was ejected from its parent body, and the melt glass held trapped gas bubbles.
Gerlind Dreibus and Heinrich Wanke of the Max Planck Institute for Chemistry in Germany estimated the chemical composition of the Martian mantle, the deep region that partially melted to produce the magmas from which SNC meteorites crystallized.
Harvey and I (University of Tennessee) independently determined that the parent magmas of SNC meteorites had about 1.
The value inferred from melt inclusions in SNC meteorites (less than 200 meters, perhaps appreciably less) might be low because it is based on only a portion of the total volume of igneous rocks.
In summary, SNC meteorites do not provide a unique answer to the question of how much water has been outgassed on Mars, but they do give new information complementing that obtained from other observations and measurements.
But the SNC meteorites also suggest that liquid water must exist underground.
Estimates of the amount of outgassed water based on the interpretation of geologic features are considerably higher than those based on atmospheric chemistry or on SNC meteorites.
In fact, report O'Keefe and Ahrens, "oblique impact-induced jet plume entrainment appears to be the only mechanism that provides the physical mechanism required to explain the acceleration to high speed of lightly shocked planetary samples such as SNC meteorites.
If the SNC meteorites truly come from Mars, what have we learned about the planet?