QUESTION:
What are the best sites at the Internet where I can find information about
the Mars Pathfinder? Is NASA planning to send more probes to Mars? When?

ANSWER from Mark Adler on June 27, 1997:
http://mpfwww.jpl.nasa.gov/

We have two under construction now to be launched in late 1998 and early
1999, an orbiter and a lander.  The orbiter will measure the movement of
water in Mars' atmosphere, and the lander will explore the expected ground
ice in Mars' Southern polar region.  We have begun the design of two more to
be launched in 2001, again an orbiter and a lander.  The orbiter will
measure water in the near surface and map the mineralogy of the planet at
high resolution.  The 2001 lander will carry a long-range rover that will
collect rocks for a later return to Earth.  We will continue the exploration
of Mars with launches every two years and two months.  That is the time
between alignments of Earth and Mars when it is economical to send
spacecraft between the two planets.

ANSWER from Donna Shirley on July 1, 1997:
There will be two missions per opportunity (every 26 months) in 96, 98, 01,
and 03 and a sample return in 2005.  Then there will be a rover in 2007 and
2011, alternating with a sample return in 2009 and 2013.

See the Mars Exploration Home Page for information on the 96 missions.
http://www.jpl.nasa.gov/mars.  The 98 orbiter will measure the atmosphere
for 1 Mars year, the lander will investigate conditions near the south pole,
including analyzing the soil. The 2001 orbiter will look for a good site for
a rover to explore and collect samples.  The 2001 and 2003 rovers will
travel several kilometers and analyze, collect and store samples for return
by the 2005 sample return mission.  The 2005 SR mission will get the first
samples back to earth in 2008 (each SR is a 3 year round trip). Later rovers
and sample returns will basically do the same pattern.

Starting in 2001 the missions will also test technologies and evaluate Mars
conditions for the design of future human missions.

Donna Shirley
Manager, Mars Exploration Program

ANSWER from Donna Shirley on July 14, 1997:
We are sending 2 missions every 26 months, including one lander per
opportunity.  All the landers are making extensive use of Pathfinder
technology.

Given our budget we cannot afford more than one per opportunity.

Donna Shirley