30 years of the Vega mission: Comparison of some properties of the 1P/Halley and 67P/Churyumov–Gerasimenko comets

On March 6 and 9, 1986, for the first time in the history of science, the Russian spacecraft Vega-1 and Vega-2 approached and closely passed by the nucleus of Halley's comet (1P/Halley). A few days later, on March 14, 1986, the same was done by the European Space Agency's (ESA) Giotto spacecraft. These missions, together with the Japanese Suisei (JAXA), marked a successful start to spacecraft exploration of cometary nuclei. Subsequent missions to other comets have been aimed at directly studying cometary bodies carrying signs of the formation of the Solar System. The Rosetta spacecraft, inserted into a low orbit around the nucleus of the 67P/Churyumov–Gerasimenko comet, performed its complex measurements from 2014 to September 2016. In this review, some of the data from these missions are compared. The review draws on the proceedings of the Vega 30th anniversary conference held at the Space Research Institute (IKI) of the Russian Academy of Sciences in March 2016 and is not meant to be exhaustive in describing mission results and problems in the physics of comets.