Don’t worry - we still do. Plenty went to Mars with the last few rovers.
Sourcing 238-Pu gets problematic at times (short half-life and I think you need a specific reactor run to create the stuff, but we do work for NASA nearly every day at the Pu facility in Los Alamos NM. Not only for space power generation but IIRC at least one rover has a heat source near each axle “bearing” to keep things warm enough to roll smoothly.
Amusing stuff. It has enough alpha-activity that the “recoil” from the emission will move contamination from the dirty areas everywhere, seemingly targeted with evil intent towards the now-cleaned ones. It literally jumps around on its own. Decon is a frustrating challenge if you make an oopsie. I’ve only worked with it once as plain old 239-Pu is interesting enough for me.
