Electronics are still more likely I think. Some sources claim [1] that even in the 1980s the Venera program had developed circuits capable of working outside o

Electronics are still more likely I think. Some sources claim [1] that even in the 1980s the Venera program had developed circuits capable of working outside of the probe's pressure hull, at Venus temperatures. I don't remember ever seeing any details on that. If I would have to guess, it was vacuum tube technology. For future probes, silicon-carbide semiconductors seem promising. Some proof-of-concept electronic instruments working at 500 C have been published in recent times [2]. [1] http://mentallandscape.com/V_Venera11.htm http://mentallandscape.com/V_Venera11.htm [2] https://ui.adsabs.harvard.edu/abs/2012LPI....43.1259H/abstract https://ui.adsabs.harvard.edu/abs/2012LPI....43.1259H/abstra...