QUESTION:
After viewing the latest data from Mars, I couldn't help but wonder why? Why
are we repeating what Viking I and II had already found 20 years ago. After
researching the data from these earlier missions I feel that we are wasting
a lot of taxpayers money!

ANSWER from Mark Adler on July 10, 1997:
"Why" is always a good question.

Actually Pathfinder and Sojourner are not repeating Viking.  First and
foremost, Pathfinder and Sojourner have shown that we can send spacecraft to
Mars and explore the surface for $260 million dollars instead of the $3600
million dollars that Viking cost.  So we are getting many times the bang for
buck for the taxpayer, and will get even more bang for the buck in
subsequent missions.  In 1998 we'll be sending two spacecraft to Mars, an
orbiter and a lander, for the price of one Pathfinder.

Second, we are exploring a very different part of Mars with very different
equipment than what Viking had.  Pathfinder landed in a site that was
(wisely) deemed too dangerous for Viking to land in.  But Pathfinder's site
is one that holds great interest in that it is an ancient flood plain into
which very old rocks from the Martian highlands were carried.  So the site
acts as a window into a Martian past when there was liquid water on the
surface and when life might have originated.  Viking had no capability to
examine the many rocks lying tantalizingly just out of reach, but the
Sojourner rover can do just that.  And Sojourner can do it with a
sophisticated instrument that was not on Viking--the Alpha Proton X-Ray
Spectrometer, which gives detailed elemental composition of the rocks. 
Furthermore, the IMP camera on the lander is far more capable than the
Viking camera, and itself provides spectroscopic information on the
surrounding terrain and rocks.

Lastly, I'm not sure what you consider to be "a lot of taxpayer's money",
but one interesting measure is to compute what fraction of the federal
budget $260 million represents over three years, and from that, how much you
contributed yourself to Pathfinder and Sojourner.  It's about 60 millionths
of what you payed each year for three years.  For myself, that came out to
about 25 cents a year for a grand total of 75 cents.