Unfathomably deep oceans on alien water worlds?

[ilan]

Unfathomably deep oceans on alien water worlds?
Paul Scott Anderson in SPACE | May 9, 2019

Distant water exoplanets might have oceans thousands of miles deep. That’s in contrast to Earth’s ocean, which is about 6.8 miles (about 11 km) deep at its deepest point.

Artist’s concept of a water world exoplanet as described in a new study. If they do exist, these distant water worlds might have global oceans much, much deeper than any in our solar system. Image via NASA/JPL-Caltech.

Water worlds – planets or moons with global oceans – used to be considered part of science fiction, but we are starting to learn now that, not only do they exist, they might actually be fairly common. In our own solar system, the moons Europa, Enceladus, Titan and Ganymede are known or suspected to have such oceans beneath their outer ice crust. Even Pluto is now thought to have one! Perhaps other worlds in our solar system have water we haven’t found yet. Scientists also think they’re getting closer to finding exoplanets – planets orbiting distant stars – that are water worlds as well, including planets with global or near-global oceans on their surfaces.

Now, a new study suggests that some exoplanet water worlds could have oceans much deeper than any in our solar system. Unfathomably deep, even, as in hundreds or thousands of miles deep. The new research was published in the Proceedings of the National Academy of Sciences (PNAS) on April 29, 2019, by Harvard University astronomer Li Zeng and his colleagues. Zeng explained that, according to the team’s computer simulations, some planets may have incredibly deep oceans:

Hundreds or thousands of kilometers … Unfathomable. Bottomless. Very deep.

Earth’s oceans are nowhere near as deep. The average ocean depth on Earth is about about 2.2 miles (3.5 km). The maximum depth is 6.8 miles (about 11 km) at the bottom of the Mariana Trench.

The data the team gathered from their computer simulations suggests that water worlds are probably common in our galaxy, particularly in sub-Neptune-sized planets – or mini-Neptunes – that have radii two to four times that of Earth but are smaller than Neptune. These planets are most likely to have deep global oceans, rather than thick atmospheres like gas dwarfs, ice giants or gas giants. Moons like Europa and Enceladus have deep subsurface oceans, for their size, but those are still not nearly as deep as the oceans that would exist on sub-Neptune worlds.
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Oceans that are hundreds or thousands of miles deep! That's unfathomable both literally and figuratively! - ilan