fission reactors in space

Wow -- somehow I didn't know until today that fission reactors have been
successfully flown in space a number of times.

Only once in the U.S.; SNAP-10A, launched in 1965, though NASA also has
a series of experimental 100 kW reactors called SAFE that have not yet
flown. But then Russia flew a number of fission-powered satellites
called RORSAT between 1967 and 1988.

I haven't gone through the specs on all of these, but for one data
point, the SAFE reactor generates 100 kW of power and masses 512 kg.

Why in the world are we considering powering lunar and Mars bases with
batteries and solar panels, when we have this kind of technology in hand?

- Joe