Two from jwz:
Soviet exploration of Venus:

The Soviet exploration of Venus, from 1961 to 1984, is the largest effort ever undertaken to study another planet. The fundamentals of interplanetary spacecraft design and remote sensing were first realized in these attempts. Successful missions included 3 atmospheric probes, 10 landings, 4 orbiters, 11 flybys or impacts, and 2 balloon probes of the clouds.

And the best part? Pictures of the planet’s surface!
[Update: it occurred to me that “Venus is pretty hot, isn’t it?”, so I looked it up. Yes, Venus is very hot: almost 500 °C. Not only that, but the surface pressure is 90 atmospheres, and the perpetual clouds are mostly sulphuric acid. The probe Venera-13 survived 127 minutes on the surface in 1982.]
PERV (porcine endogenous retrovirus) can be transmitted to human cells from the pig/human chimeric cells that form in pigs grown from embryos into which human stem cells have been injected. One of the aims of the research is (was) to create tissues that could be used in xenotransplantation. Some researchers would disagree with me:

…the question is how widespread and how many of these hybrid cells were found? If they are very rare – and we haven’t found any in our experiments – then I don’t think it is that important.

but I think this is the end of porcine xenotransplants.