QUESTION:
I hear how scientists analyzed the air samples in meteorites
from Mars.  Why is that important and how is it done?

ANSWER from Dr. Robert Anderson on December 7, 1996:
When a magma (lava) cools little bubbles of gas become trapped within 
the rock.  By analyzing the gas, we can get a quick look at what the 
atmosphere was like when the rock cooled.  There are several techniques
used on Earth to analyzse gases such as X-ray Flourence, mass 
spectrometers, etc.