How do scientists measure the composition of the Earth's early atmosphere?

Answer 1

The Antarctic is one of the last unspoiled areas on earth. Air gets trapped in packed snow fall, later gets very packed, sometimes slightly melted, but not enough for the air to get out. This process has gone on for millions of years. When scientists take ice core samples, it is for the air that is trapped, deep down, where it was trapped millions of years ago. They take these samples, into a laboratory, where they carefully extract the air samples. Then they will use a gas chromatograph, IR spectrum analyzer, or other instrumentation to determine the composition of the air sample. The depth of the ice core determines the age of the earth at the time, and with the many ice core samples taken, there are many to compare it to for which to make a better determination.