It appears as though a liquid ocean
is presently underneath Sputnik Planitia on the dwarf planet Pluto. It
was believed that the temperate needed for an ocean to remain in liquid
format on Pluto would have been too high because the thick ice would
have melted. However, Japanese astronomers claim there is a layer of gas
located underneath the ice and above the liquid which works as a type
of insulation between the two.
Pluto in all of its phases
This is very exciting news for scientists as they previously believed
that all the water on Pluto would have been in a frozen state. The
research, which was published in
Nature Geoscience,
read in part, “To maintain an ocean, Pluto needs to retain heat inside.
On the other hand, to maintain large variations in its thickness,
Pluto’s ice shell needs to be cold.” Additionally, they wrote, “Here we
show… that the presence of a thin layer of clathrate hydrates (gas
hydrates) at the base of the ice shell can explain both the long-term
survival of the ocean and the maintenance of shell thickness contrasts.”
They better explained how the clathrate hydrates work by writing,
“Clathrate hydrates act as a thermal insulator, preventing the ocean
from completely freezing while keeping the ice shell cold and immobile.”
As for the type of gas, they explained that “The most likely
clathrate guest gas is methane, derived from precursor bodies and/or
cracking of organic materials in the hot rocky core. Nitrogen molecules
initially contained and/or produced later in the core would probably not
be trapped as clathrate hydrates, instead supplying the nitrogen-rich
surface and atmosphere.”
Pluto’s size compared to Earth
Researchers created a simulation of Pluto’s evolution, with and
without a gas hydrate layer between the ice and the ocean in order to
calculate how long it would take for the subsurface oceans to freeze
over. They calculated that without the gas hydrate layer, the ocean
would have been totally frozen around 800 million years ago. However,
with the gas hydrate layer, the ocean hardly froze at all. In
conclusion, without a gas hydrate layer, it would have taken the
subsurface ocean approximately 100 million years to freeze over, but
with the gas layer, it would take more than a billion years.
The simulation based on observations conducted by New Horizons not
only shows the real possibility of a liquid ocean on Pluto, but it also
gives a plausible explanation as to how the most iciest planets can
still contain water in liquid format
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