Mystery behind formation of surface ice-shapes on Pluto unraveled

Date:
December 15, 2021
Source:
University of Exeter
Summary:
Scientists have unraveled a fascinating new insight into how the
landscape of the dwarf-planet Pluto has formed.



FULL STORY ========================================================================== Scientists have unravelled a fascinating new insight into how the
landscape of the dwarf-planet Pluto has formed.


==========================================================================
A team of international researchers, including Dr Adrien Morison from
the University of Exeter, has shown how vast ice forms have been shaped
in one of the planet's largest craters, Sputnik Planita.

Perhaps the most striking feature on Pluto's surface, Sputnik Planitia
is an impact crater, consisting of a bright plain, slightly larger than
France, and filled with nitrogen ice.

For the new study, researchers have used sophisticated modelling
techniques to show that these ice forms, polygonal in shape, are formed
by the sublimation of ice -- a phenomenon where the solid ice is able
to turn into gas without going through a liquid state.

The research team show this sublimation of the nitrogen ice powers
convection in the ice layer of Sputnik Planitia by cooling down its
surface.

The research is published in the leading journal Nature on Wednesday,
December 15th 2021.

Dr Morison, a Research Fellow from Exeter's Physics and Astronomy
department said: "When the space probe New Horizon performed the only,
to date, fly-by of Pluto in 2015, the collected data was enough to
drastically change our understanding of this remote world.

"In particular, it showed that Pluto is still geologically active
despite being far away from the Sun and having limited internal energy
sources. This included at Sputnik Planitia, where the surface conditions
allow the gaseous nitrogen in its atmosphere to coexist with solid
nitrogen.

"We know that the surface of the ice exhibits remarkable polygonal
features - - formed by thermal convection in the nitrogen ice, constantly organizing and renewing the surface of the ice. However, there remained questions behind just how this process could occur." In the new study,
the research team conducted a series of numerical simulations that showed
the cooling from sublimation is able to power convection in a way that
is consistent with numerous data coming from New Horizons -- including
the size of polygons, amplitude of topography and surface velocities.

It is also consistent with the timescale at which climate models predict sublimation of Sputnik Planitia, beginning around 1 -- 2 million years
ago. It showed that the dynamics of this nitrogen ice layer echo those
found on Earth's oceans, being driven by the climate.

Such climate-powered dynamics of a solid layer could also occur at the
surface of other planetary bodies, such as Triton (one of Neptune's
moons), or Eris and Makemake (from Kuiper's Belt).

========================================================================== Story Source: Materials provided by University_of_Exeter. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Adrien Morison, Ste'phane Labrosse, Gae"l
Choblet. Sublimation-driven
convection in Sputnik Planitia on Pluto. Nature, 2021; 600 (7889):
419 DOI: 10.1038/s41586-021-04095-w ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/12/211215132646.htm

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