Because it is the principal component of Earth's hydrosphere, the world ocean is integral to all known life, forms part of the carbon cycle, and influences climate and weather patterns. It is the habitat of 230,000 known species, although much of the oceans depths remain unexplored, and over two million marine species are estimated to exist.[9] The origin of Earth's oceans remains unknown; oceans are believed to have formed in the Hadean period and may have been the impetus for the emergence of life.