QUESTION:
One of the questions regarding the Rover's batteries made me wonder why NASA
isn't using some form of rechargable batteries, where the solar panels not
only allowed operation but recharged the batteries so night time operations
could continue. Is the technology not quite there yet?

ANSWER from David Dubov:
Certainly NASA (and other) missions have flown with rechargeable batteries
for many years. However, at the time of the design of the Sojourner rover, a
low mass/low complexity (in terms of electronics, operating temperature)/low
cost solution for rechargeable batteries was not available. In addition, the
7 sol primary/30 sol extended mission requirement could be met by the
primary batteries selected. Recent advances in battery technology would make
us rethink this design for a future rover - particularly one with a longer
life requirement.