From Srimad-Bhagavatam we understand that there are various oceans. Somewhere there is an ocean filled with milk, somewhere an ocean of liquor, an ocean of ghee, an ocean of oil, and an ocean of sweet water. Thus there are different varieties of oceans within this universe. The modern scientists, who have only limited experience, cannot defy these statements; they cannot give us full information about any planet, even the planet on which we live. From this verse, however, we can understand that if the valleys of some mountains are washed with milk, this produces emeralds. No one has the ability to imitate the activities of material nature as conducted by the Supreme Personality of Godhead. In the Siddhanta-Siromani, an astrological text, the different oceans are described as follows: (1) the ocean of salt water, (2) the ocean of milk, (3) the ocean of yogurt, (4) the ocean of clarified butter, (5) the ocean of sugarcane juice, (6) the ocean of liquor and (7) the ocean of sweet water. On the southern side of the ocean of salt water is the ocean of milk, where Lord Kshirodakasayi Vishnu resides. He is worshiped there by demigods like Brahma. It is also called as Svetadvipa. Purusa-sukta is the standard prayer which the demigods recite to appease the Supreme Personality of Godhead, Kshrirodakasayi Vishnu. Because He is lying on the ocean of milk, He is called Kshirodakasayi Vishnu. He is the Supreme Personality of Godhead, through whom all the incarnations within this universe appear.
These are described in the Srimad-Bhagavatam as sapta-dvipa. Dvipa means island. All these planets are sometimes described in the Vedic literature as dvipas. The planet on which we are living is called Jambudvipa. Outer space is taken as a great ocean of air, and within that great ocean of air there are many islands, which are the different planets. There are different kinds of mountains also. Each and every planet has a different type of atmosphere.
Ref >> Srila Prabhupada Vani.