Final answer:
Saturn's moon Enceladus has an underground ocean that may contain twice the amount of water found in Earth's oceans, making it a significant point of interest for astrobiology.
Step-by-step explanation:
The celestial body with a 'secret' underground ocean containing twice the amount of water that Earth has in all the oceans is Saturn's moon Enceladus. In 2015, the Cassini mission's scientists identified a subsurface ocean under the icy crust of Enceladus, which is feeding massive geysers that spew water into space.
This discovery has implications for astrobiology, as it adds Enceladus to the list of celestial bodies to explore for possible life. Unlike Europa's deeply buried ocean under a thick ice crust, Enceladus' water jets make sampling its ocean more feasible. Further investigations into Enceladus's ocean, and its comparison with other icy moons like Europa, continue to intrigue scientists in the quest for habitable environments beyond Earth.
Enceladus, a moon of Saturn, has a 'secret' underground ocean containing twice the amount of water that Earth has in all the oceans. This was tentatively identified by the Cassini mission scientists in 2015. Enceladus has geysers that release water from its subsurface ocean, making it more accessible for study compared to the ocean of Europa, which is buried below a thick ice crust.