Pluto's Icy Exterior May Hide a Deep, Dense Underground Ocean, Study Suggests

Pluto's surface, a dwarf planet shivering at a freezing -364°F (-220°C), is covered in layers of nitrogen ice.

However, a recent study suggests that beneath this frozen exterior, there may be a dense, deep ocean of liquid water. This ocean offers fascinating possibilities about the far-off globe because it may be thicker than seawater on Earth and more profound than the planet's crust.

Evidence and Model of an Underground Ocean in Pluto

It may seem improbable, even absurd, to entertain the notion of liquid water on a planet as frigid and distant as Pluto. However, the data gathered by NASA's New Horizons spacecraft has provided compelling evidence of an underground ocean, challenging our preconceived notions.

Pluto is notable for lacking an equatorial bulge, a characteristic that forms less frequently on planets with liquid interiors. Moreover, Pluto's icy surface looks broken, maybe from liquid water expanding and freezing under the nitrogen ice.

Some scientists say Pluto is home to cryovolcanoes that release solid ice or water vapor, offering additional evidence. This water comes from underneath Pluto's surface, suggesting that there may be a layer of liquid water there.

Researchers have constructed a theoretical model of this underground ocean through meticulous research. Leveraging mathematical models from Washington University in St. Louis and the Lunar and Planetary Institute in Houston, they focused on Sputnik Planitia, a basin on Pluto's surface shaped like a heart, believed to have been formed by a long-ago impact.

To match the observed fractures in Sputnik Planitia, the researchers experimented with different combinations of ocean thickness and water density.

One of the study's authors, Alex Nguyen, a graduate student at Washington University in St. Louis, explained that their calculations indicated Pluto's ocean was likely between 25 and 50 miles (40 to 80 kilometers) thick and about 8% denser than Earth's seawater, comparable to the salinity of the Great Salt Lake. They estimated a "sort of Goldilocks zone where the density and shell thickness is just right."

Controversy and Further Research: Planetary Researchers' Insights

The hypothesis of a Plutonian ocean is still debatable in light of these observations. According to the scientists studying Pluto, there is not enough evidence to prove that liquid water exists beneath Pluto's surface. The basin may have formed even if Pluto's interior was solid, with a recent simulation of Sputnik Planitia's formation as their basis.

The nature of Pluto's interior will remain a mystery until a spacecraft capable of returning to the planet after New Horizons can investigate it. However, Nguyen and co-author Patrick McGovern's work, published in the journal Icarus, has added a crucial piece to the puzzle.

High-resolution images from New Horizons were examined by the planetary scientists from Washington University in St. Louis and the Lunar and Planetary Institute, looking into the possibility of an underground ocean in a better view. These images show Pluto's varied hues and geological characteristics, which aided the scientists in assembling the mysteries of the planet's history.

For many years, it was believed that Pluto couldn't sustain an ocean due to its extraordinarily low temperatures. Nguyen explained that, as a small body, Pluto should have lost almost all of its heat shortly after it was formed, leading basic calculations to suggest it would be frozen solid to its core.

However, recent evidence, such as the discovery of cryovolcanoes, contradicts this assumption. Nguyen and McGovern's mathematical models explain the cracks and bulges in Pluto's ice, indicating a subsurface ocean protected by a thick shell of water ice.

This layer likely prevents the ocean from freezing solid. Their models also suggest the ocean's density, supporting the hypothesis that it is around 8% denser than Earth's seawater.

Many of Pluto's mysteries will remain unknown to future generations as there are no preparations for a return expedition to the planet. Nguyen underlined that Pluto is a world worth researching, whether called a planet, planetoid, or just one of many objects in the farthest limits of the Solar System.

For Nguyen and many others, Pluto will always merit further investigation. This work challenges our knowledge of this far-off planet by providing a fascinating peek into what might be beneath Pluto's frozen surface, something we hope future expeditions will explore further.

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