Kask graduated from the University of Tartu in 1971 with a degree in physics.
He worked at the National Institute of Chemical Physics and Biophysics from its creation until 1990.
His field of research is fluorescence-based detection techniques for molecules.
Kask helped with many of the findings of the application of the German company Evotech-Technologies products.
He was one of the leaders of the Popular Front of Estonia, as well as Rein Taagepera, a campaign manager in the presidential election in 1992.