Scientifically, the Indian Ocean remained poorly explored before the International Indian Ocean Expedition in the early 1960s. The Challenger expedition 1872–1876 only reported from south of the polar front. The Valdivia expedition 1898–1899 made deep samples in the Indian Ocean. In the 1930s, the John Murray Expedition mainly studied shallow-water habitats. The Swedish Deep Sea Expedition 1947–1948 also sampled the Indian Ocean on its global tour and the Danish Galathea sampled deep-water fauna from Sri Lanka to South Africa on its second expedition 1950–1952. The Soviet research vessel Vityaz also did research in the Indian Ocean.