In article , James G wrote:
One thing I have never seen addressed or maybe I missed it when there
was a big hub-bub about it, but...

How do they *know* these meteorites actually came from Mars?

Even if they have the right spectral and chemical composition, a rock
is a rock isn't it?

An article on the SNC meteorites - the group of "known" Mars-originating
meteorites - can be found at

http://scienceworld.wolfram.com/astr...eteorites.html

(They announced the identification of another one quite recently, IIRC -
we're up to about 30. http://www.jpl.nasa.gov/snc/ has a list)

--
-Andrew Gray