One of the most famous incarnations of Vishnu is Kurma the tortoise, who helped the gods during the Churning of the Ocean. Now I had always assumed that the story of the churning of the ocean only took place in the Chakshusha Manvantara. For those who don't know, the four Yugas together make up one Mahayuga, and a thousand Mahayugas make up one Kalpa or day of Brahma. But as I discuss in this answer, a Kalpa is also divided into fourteen periods called Manvantaras, and during each Manvantara humanity is ruled by a different Manu, there is a different Indra ruling the three world, there is a different set of Saptarishis, etc.
Now we are living in the seventh Manvantara of the present Kalpa, known as the Vaivasvata Manvantara. And I thought that the Churning of the Ocean only took place in the Chakshusha Manvantara. For instance, this chapter and subsequent chapters of the Srimad Bhagavatam describes the story of the Churning of the Ocean which took place in the Chakshusha Manvantara:
The son of Cakṣu known as Cākṣuṣa was the sixth Manu. He had many sons, headed by Pūru, Pūruṣa and Sudyumna. During the reign of Cākṣuṣa Manu, the King of heaven was known as Mantradruma. Among the demigods were the Āpyas, and among the great sages were Haviṣmān and Vīraka. In this sixth manvantara millennium, Lord Viṣṇu, the master of the universe, appeared in His partial expansion. He was begotten by Vairāja in the womb of his wife, Devasambhūti, and His name was Ajita. By churning the Ocean of Milk, Ajita produced nectar for the demigods. In the form of a tortoise, He moved here and there, carrying on His back the great mountain known as Mandara.
But now I think this may not be the only time that the story of the Churning of the Ocean took place.
In this chapter and subsequent chapters of the Bala Kanda of the Ramayana, Vishwamitra tells Rama and Lakshmana a story about the Churning of the Ocean:
Oh, Rama, I tell of the legend of Indra as I was told and listen to it as I tell. What really chanced in this country, oh, Raghava, that be listened in its quintessence. *Once in Krita era, oh, Rama, the sons of Lady Diti were extremely energetic ones in their brawniness, whereas the sons of her younger sister Lady Aditi were venerable, vigorous and highly righteous ones.** Oh, tigerly-man, Rama, there was a thinking to those great-souls then, as to 'how we shall [thrive] deathless, ageless and wasteless...' Thus thought the sons of Diti and Aditi. For them who were thinking thus on that subject a thought occurred to those masterminds, 'on churning the Milky Ocean, therein we get its elixir, indeed. Then on deciding to churn the Milky Ocean, they made Vasuki, the mighty King of Snakes, with thousand heads, as the churning rope and Mt. Mandara as stirrer and those who have unlimited energy started churning the Milky Ocean.
Now the Adityas, i.e. the sons of Aditi, were not the gods who ruled in the Chakshusha Manvantara, rather they're the gods ruling right now in the Vaivasvata Manvantara. So my question is, did the Churning of the Ocean happen again in one of the Satya Yugas of the Vaivasvata Manvantara?
If it did happen more than once, that would explain a long-standing confusion I've had: Garuda transported mount Mandara to the ocean of milk, and the churning of the ocean produced the flying horse Ucchaishravas. Yet before Garuda was born, Garuda's mother Vinata and her co-wife Kadru had a bet over the color of Ucchaishravas' tail as he was flying through the sky. Perhaps this sort of thing can be explained by the Ucchaishravas that Vinata and Kadru bet on being from a previous Churning of the Ocean.
On a side note, given that Vishwamitra is telling the story of the Churning of the Ocean to Rama, is it possible that the story is described in the Vedas?
