The Solar System could be a softer place than we thought of the front – even in the very cold parts of the Kuiper Belt. There, Pluto's dwarf plate could be the harbor of liquid oceans under a shell of nitrogen ice.
It was thought that the temperature required to maintain a liquid ocean on Pluto was too high for the thick ice to remain un melted, but Japanese astronomers have found a new possibility: A layer of gas beneath the ice and above. fluid, insulating both of each other, and allowing them to live.
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This could help resolve the gravity anomaly found by the New Horizons probe in the form of Sputnik Planitia, with its equatorial position and low topography, suggesting a liquid ocean beneath.
A liquid ocean under Sputnik Planitia could also explain tectonic features on the planet. Yet, based on Pluto's age and location, scientists expected that all liquids should be frozen solid.
"To maintain an ocean, Pluto needs to keep the heat in. On the other hand, to maintain large variations in thickness, Pluto's ice shell needs to be cold," the researchers wrote in their paper. .
"Here we show … that the presence of a thin layer of clathrate hydrates (gas hydrates) at the bottom of the ice shell can explain the long-term survival of the ocean and maintain shell density contrasts."
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The team assumed that a gas hydration layer – a type of solid water, similar to ice with gas had been tied in a lattice made from its molecules, was also called glathrate – responsible. But obviously we can't go over to Pluto to check things, so they were relying on computer simulations.
Starting 4.6 billion years ago, the Solar System age, the researchers evolved Pluto's evolution, with a gas hydration layer between the icy shell that covers the Planitia, and the ocean underneath it.
They modeled the thermal evolution of the small planet, and calculated how much time it would take for sub-surface oceans to freeze and form an ice shell of uniform thickness.
Without the gas hydrate layer, they saw that the ocean – as expected – would have completely frozen around 800 million years ago, as the Earth's first animals were starting to emerge.
But that wasn't true in the simulation that contained gas hydrate. He showed that, after insulating a layer of gas, the ocean was barely freezing. When a thick uniform ice layer took about 100 million years to freeze without a gas hydration layer, the addition of such a layer increased that time to over a billion years.
Although the ice covered the Sputnik Planitia is mostly nitrogen frost, the most likely candidate for that gas clathrate would be methane from Pluto's rocky core – making that insulation that huge fund t of what we know on Earth as flammable ice.
"Hydration fluid acts as a thermal insulator, preventing the sea from completely freezing while keeping the ice shell cold and immobilized," the researchers wrote.
"The most likely endowment gas is methane, derived from precursor bodies and / or splitting organic materials into the hot rocky core. Nitrogen molecules contained and produced later would probably not be in the core. are caught as clathrate hydrates, rather supply the surface and the atmosphere that is full of nitrogen-rich. "
It doesn't just support the observations made by New Horizons and the possibility of a liquid ocean on Pluto that has the simulation.
It also shows how liquid oceans can exist even on the youngest planets and planes. The Universe could be a much softer place than we thought.
The research has been published in Geoscience Nature.