An ocean for Pluto and a thinner ice shell on Enceladus
Source: Astronomy Magazine
An ocean for Pluto and a thinner ice shell on Enceladus
Plenty of good news for our ocean worlds!
By John Wenz | Published: Wednesday, June 22, 2016
Once, we thought earth was the only planet with oceans. But now, we're seemingly finding them everywhere in our solar system, including possibly the last place on anybody's mind: Pluto.
New evidence published in Geophysical Research Letters shows that the icy dwarf planet may still have a liquid ocean lurking underneath its frozen exterior. Tectonic activity on the surface of Pluto, revealed by NASA's New Horizons spacecraft, shows an absence of contraction in the surface. Contraction is the kind of thing that would be expected if the ocean had, at the depths it's believed to be at, frozen completely into a dense form of ice called Ice II. That seems to indicate it's liquid or at least slushy down there.
Radioactive elements in the core (along with some motion from the tug-o-war between Pluto and Charon) would keep the ocean warm. There's still some chance, though, that the ice crust of Pluto is thinner than anticipated, which would lead to formation of less dense forms of ice. But flows of nitrogen ices seem to come from much deeper below, placing the ice shell as much as 300 km (186 mi) from the surface. At those depths, if there was water, it would almost certainly form Ice II. That is, unless something made it not freeze.
Of course, we already know that Enceladus, a moon of Saturn, is an ocean world, with warm water under the ice shell spewing into space thanks to the gravitational tug of Saturn. Pluto joins that pantheon now, along with worlds like Ganymede, Europa, and Titan. But unlike Pluto, new evidence seems to indicate that Enceladus may have a much thinner ice shell than once believed.
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Read more: http://www.astronomy.com/news/2016/06/an-ocean-for-pluto-and-a-thinner-ice-shell-on-enceladus
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Related: Recent Tectonic Activity on Pluto Driven by Phase Changes in the Ice Shell (Geophysical Research Letters)
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Source: Smithsonian.com
New Evidence Strengthens the Case for Pluto's Underground Ocean
Features on the dwarf planet's smooth surface suggest
that not all is frozen on that tiny, distant world
By Marissa Fessenden
smithsonian.com
June 22, 2016 2:52PM
From far in the chilly depths of our solar system, the dwarf planet Pluto keeps scientists on their toes—from its exotic ices to its chilly heart. Now, new computer modeling supports that idea that the tiny world harbors a liquid ocean between it's rocky core and outer shell of ice.
Ever since the New Horizon's Probe swung by Pluto last year, scientists have wondered if a liquid ocean could be "sloshing around under its icy crust," writes Kevin Stacey in a press release. But a new study, published in Geophysical Research Letters, suggests that this ocean is indeed a reality.
The team of Brown University researchers used computer simulations to show that if the global liquid ocean had solidified, the heavy outer ice shell would have crushed the freezing ocean into a strange type of ice called ice-II. Unlike typical ice, which expands as it freezes, ice-II takes up less volume than liquid water. As a result, the entire dwarf planet would have shrunk, causing the surface shell to buckle and scrunch up in distinctive ways, "like the skin of an overripe peach wrinkling as it dries," writes Conor Gearin for New Scientist.
Instead, the New Horizon's probe recorded deep cracks marking Pluto's surface. That leads researchers to conclude that something, perhaps heat radiating from radioactive elements in the dwarf planet's core, is keeping the ocean on Pluto wet.
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Read more: http://www.smithsonianmag.com/smart-news/new-evidence-strengthens-case-wet-ocean-beneath-plutos-surface-180959534/?no-ist
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