QUESTION: 
How will the Sojourner be powered?  Will it be by battery or solar power?  

ANSWER from Robert Manning on February 24, 1997:
Yes! The Sojourner rover is primarily powered by a solar panel on the "roof" of
the rover. The panel consists of an array of gallium arsenide solar cells that
produce electric current in proportion to the number of photons that come from
the sun. The rover also carries a set of primary (non-rechargable) lithium
batteries that are used to power the rover during night time operations (for
example, the rover calls the lander occasionally throughout the night to update
its knowledge of the time). The batteries can also power the rover during
daytime traverses if the solar arrays happened to get tilted away from the sun
for some reason (e.g. scaling a small crater).