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00:04 This is the smallest of Saturn's major moons, called Mimas.
00:07 However, while it's comparatively diminutive, it just got a whole lot more interesting to scientists,
00:12 as they say that contrary to previous beliefs, Mimas likely has a massive liquid ocean under its surface.
00:18 It was previously believed that because of its cratered outside, it must be a solid moon of ice.
00:22 That's because astronomers predicted that any moon that was as pockmarked and cratered as Mimas must be solid,
00:28 as a non-solid moon would fissure during asteroid impacts.
00:31 However, Mimas has another peculiarity that has led experts to a new conclusion.
00:35 It wobbles during its orbit around Saturn.
00:38 Using observational data from the Cassini probe,
00:40 researchers built a computer simulation and tested the global subsurface ocean theory against a solid core theory,
00:46 finding that not only is it more likely than not that Mimas has liquid oceans under its icy exterior,
00:51 but that liquid ocean is young, only around 25 million years old.
00:54 Experts say their best guess for why an ocean suddenly began to form there after billions of years
00:59 is due to how large planetary objects interact gravitationally in space.
01:03 Gravity can cause the internals of an object to be stressed, creating friction and warming them.
01:07 This is why Jupiter's moon Io is so volcanic,
01:10 being pulled on either side by the largest planet in the solar system and two of its other moons.
01:14 And it's the best guess for why Mimas might be getting warmer from the inside out.
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