February 6, 2004
A: FROM MENTOR JOAN LUSK IN RI
The short answer is that we detect the elements far from earth by
spectroscopy. In stars, the cooler elements at the surface absorb light on
its way from the interior, leaving dark lines in the spectrum we see from
earth. These were named for Fraunhofer and you can see a description at
http://www.harmsy.freeuk.com/fraunhofer.html The fact that elements on
earth absorb light at the same frequencies was a major indication that
start are made of the same elements as the earth.

http://search.nap.edu/oneuniverse/ Gives a broad introduction, including
information about elemental composition.

Other forms of spectroscopy have given information about the planets, and
now the landers on Mars are giving us more. Here's a link to the latest news.
http://amesnews.arc.nasa.gov/