1. The Rosetta spacecraft landed Philae on a comet in 2014, taking measurements. Philae awoke again in summer 2015 to continue communicating.
2. New Horizons launched in 2006 and reached Pluto in 2015, throughout major world events. It had a small CPU but continued its mission.
3. NASA confirmed in 2015 that liquid water runs on Mars' surface during summer, potentially indicating life.
4. Scientists discovered two potential Earth-sized planets beyond Pluto in our solar system in 2015, which could revolutionize astronomy.