NASA’s Image of the Day for April 5, 2016 shows the waters of the north Atlantic Ocean:
In recent years humanity has learned that oceans are not unique to Earth. Discoveries of them on Saturn’s moons Enceladus and Titan and Jupiter’s moon Europa indicate that oceans may actually be ubiquitous in our solar system.
Now, it seems, it is possible that an ocean once existed on a satellite of the dwarf planet Pluto.
NASA said Friday that images obtained by the New Horizons probe suggest that Charon once had a subsurface sea that expanded outward as it froze, cracking the surface of the moon.
The photographs show tectonic faults, including some valleys more than 6.5 kilometers deep, that indicate an expansion of Charon sometime in the past.
Here’s how it likely happened:
The outer-most layer of Charon, including its surface, is now water ice. But the satellite’s internal heat would have caused that ice to melt deep under the surface, which would have resulted in a subsurface ocean. As the decay of radioactive elements that constitute Charon’s structure subsided, and as the rocky object cooled as the time since its formation passed, that ocean would have frozen. Just as the change of water’s state from liquid to solid on Earth causes an increase in the the compound’s volume, ice formation under the surface of Charon would have pushed the surface outward, resulting in the valleys and also numerous ridges and scarps.