QUESTION:
Why don't you use a radioisotope thermoelectric generator (RTG) on the
Huygens Probe for longer probe life?

ANSWER from FAQ on June 3, 1999:
Unlike the Cassini orbiter which will conduct a wide variety of science
investigations of Saturn and its satellites for four years, the Huygens
probe's mission is focused strictly on studying the chemistry, winds
and structure of Titan's atmosphere. While the Probe does have some
surface science capabilities and will image the surface during descent,
it lands relatively hard (at about 25 km per hour or 15 mph) and has no
real assurance of surviving a landing on Titan's surface. As a result,
ESA has designed the Probe for a short duration mission that relies on
batteries, as opposed to long-duration (and significantly more
expensive) RTGs.