Quote:
Originally Posted by Robh
Interesting!
Apart from the contamination issue, I have some other questions. (Carl, please note: I'm not expecting you to answer them) ...
They say that the meteorites are Martian because the gases inside them match the Martian atmosphere. How do they know what the Martian atmosphere was like billions of years ago? They don't have core samples.
Presumably, a large body (asteroid) hit Mars and sent these smaller bodies into space, eventually landing on Earth as meteorites. How do we know that the meteorites did not originate from the impact body?
Regards, Rob.
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I will answer them, though
They look for trapped gases in mineral grains within the rocks. You can tell from running a gas chromatograph analysis of the air trapped in inclusions within the mineral grains what the surrounding gases were when the rocks were either being formed, or with sediments, when the rocks were last exposed to atmospheric gases at or near the surface. In some cases where liquids are trapped in the inclusions, using an ion microprobe on the inclusions can determine what the composition of that liquid is. They can tell from composition and isotopic analysis what gases are in the inclusions, how old the inclusions were when they formed, where they come from and what differences there are between the present and what the previous conditions under which they formed were like.
In answer to your second question....the petrology and geochemistry of the rocks. They're different for Mars and any possible impacting bodies, so the differences can be determined. Not only that, but the impacting body was most likely completely destroyed, whereas some Martian material would've survived, to be blasted into space. Any impactor would've been completely melted and its rocks recrystallised, however the bulk composition would remain basically the same. Any impactor bits that may have come here, they would be able to distinguish them from true Martian materials.