The Cassini spacecraft, that has been mining the Saturnine system for information for the last 10+ years, reached the end of its operational life and was destroyed by dropping it through the atmosphere of Saturn.
Cassini has had such a profound impact on our knowledge about our solar system that the amount learned in the last 20 years dwarfs everything known about Saturn prior. You would probably not be far off saying that everything that we know about the Saturnine system is because of Cassini.
So, why would they suicide such a remarkably productive and successful mission? Get this- They have discovered prebiotic planetoids among Saturn’s moons. That is, moons that might have the conditions for biological life – and they didn’t want to leave the spacecraft hanging out to crash into one of those prebiotic moons and pollute it!
They made their considerations based on Leave No Trace!