I'm positive this was from a Japanese show/movie that was brought to the USA.
I remember watching it on (I think) WNUVTV 54 (or maybe channel 45) when I lived in Baltimore, MD sometime in the early 1980's.
It was in color (not colorized). The cast was all-Japanese and the show was from Japan, dubbed and brought to the USA.
There were a couple astronauts coming back to Earth in a reentry capsule, but when it was found and opened there were just two skeletons in it. One of them was holding a cube in it's hand. Anyone that touched the cube was reduced to a skeleton as well (this happened several times throughout the episode/movie.
That's mostly what I clearly remember. I thought it was an Ultraman episode, or maybe Jet Jaguar, but I've never been able to find it. I've re-watched all the Ultraman episodes from that time-frame and haven't found it.
I've also started watching Ambassador Magma (The Space Giants in the USA) but so far I haven't found it.
Anyone have any idea what show and episode or movie I'm talking about? I've tried a few other sites with no luck so far.