NatGeo: Pluto Has Oceans Under Ice?

[bystander]

Pluto Has Oceans Under Ice?
National Geographic | 16 Dec 2010

Radioactive heat may warm Pluto's core, model suggests.

Pluto (center) and its three known moons, Charon, Nix, and Hydra. [i](Credit: NASA/ESA/H. Weaver (JHU/APL)/A. Stern (SwRI)/HST Pluto Companion Search Team)[/i]

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Frigid Pluto, home to some of our solar system's chilliest real estate, may well harbor an ocean beneath its miles-thick ice shell, new research suggests.

Despite its extreme cold, the dwarf planet still appears to be warm enough to "easily" have a subsurface ocean, according to a new model of the rate at which radioactive heat might still warm Pluto's core.

And that ocean wouldn't be a mere puddle, noted planetary scientist Guillaume Robuchon of the University of California, Santa Cruz.

Rather, the ocean could be 60 to 105 miles (100 to 170 kilometers) thick beneath a 120-mile (200-kilometer) layer of ice, Robuchon said at an annual meeting of the American Geophysical Union in San Francisco earlier this week.

If so, Pluto would join a list of outer solar system bodies—such as Saturn's moons Titan and Enceladus—believed to possibly hold liquid water, a key ingredient for life as we know it.

Pluto's heat would come from the decay of radioactive nuclides, particularly potassium-40, in rocks deep in the dwarf planet's interior.

This is for you, Orin

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Pluto Has Oceans Under Ice?
National Geographic | 16 Dec 2010

Radioactive heat may warm Pluto's core, model suggests.

Pluto's heat would come from the decay of radioactive nuclides, particularly potassium-40, in rocks deep in the dwarf planet's interior.

Potassium-40 is the largest source of
natural radioactivity in both animals & people.

<<Potassium-40 (⁴⁰K) is a rare radioactive isotope of potassium which has a very long half life of 1.248×10⁹ yr. It is a rare example of an isotope which undergoes all three types of beta decay (β−, β+ and electron capture). About 89% of the time ⁴⁰K decays to calcium-40 (⁴⁰Ca). However, 11% of the time it decays to argon-40 (⁴⁰Ar).

Potassium-40 is especially important in potassium–argon dating (K–Ar dating). When rocks melt into lava, it releases argon it previously contained, thus will be an argon-free rock when it cools down. If a cooled rock contains any potassium-40, then argon-40 will build up over time as the remaining ⁴⁰K decays. This created argon cannot escape from the solid rock. The lifetimes of ⁴⁰K and ⁴⁰Ar are well known, thus it is then possible to determine the time elapsed since the rock last cooled by measuring the levels of ⁴⁰K and ⁴⁰Ar contained in the rock. Despite trapping of ⁴⁰Ar in many rocks, it can be released by melting, grinding, and diffusion. Almost all of the argon in the Earth's atmosphere is the product of potassium-40 decay, since 99.6% of Earth atmosphere argon is ⁴⁰Ar, whereas in the Sun and presumably in primordial star-forming clouds, argon consists of < 15% ⁴⁰Ar and mostly (85%) ³⁶Ar.>>