Prior to 2015, scientists knew little about Pluto, mainly because it is dim and small from Earth’s perspective, not to mention 4.67 billion miles away.
When NASA’s New Horizons space probe flew by the far-away dwarf planet, imaging it in unprecedented detail, the historic mission raised more questions than answers. For one, the probe’s findings raised suspicions that some of Pluto’s mountains were formed on a bedrock of water ice.
According to a new study, computer simulations provide have provided compelling evidence that an insulating layer near the surface is keeping a subsurface ocean from freezing beneath Pluto’s ice. In other words, there could be a liquid ocean on the planet.
A team of Japanese scientists published the study, proposing that such an otherworldly idea is possible because a thin layer of ice containing trapped gas molecules, known as gas hydrates, at the bottom of the ice shell could be insulating the ocean. By calculating Pluto’s temperature and the thickness of the ice shell, the scientists concluded that the gas hydrates would be enough to maintain a subsurface ocean.
Understanding how a subsurface ocean can exist on Pluto will provide scientists with invaluable information to better understand how similar bodies of water can exist on other planets, too. Liquid water oceans are thought to exist inside icy satellites of gas giants such as Europa and Enceladus. Understanding the survival of subsurface oceans is of fundamental importance not only to planetary science but also to astrobiology.
Scientists have been repeatedly surprised and bewildered by the data New Horizons collected and processed from its flyby in 2015. Even the initial photos showed unexpected complexity of the dwarf planet.
The study is published in in the journal Nature Geoscience.
Pluto is the smallest, coldest and most distant dwarf planet with an atmosphere in the Solar System. It orbits the Sun every 248 years, and its surface temperature is between -378 and -396 degrees Fahrenheit (-228 to -238 degrees Celsius). Its atmosphere consists of nitrogen, with traces of methane and carbon monoxide.
Scientists aimed to record the seasonal evolution of Pluto’s surface pressure by observing ground-based stellar occultations to gain the atmosphere’s profile including density, pressure and temperature. They were able to construct seasonal models of Pluto and how it responds to changes with the amount of sunlight it receives as it orbits the Sun. What they found was when Pluto is farthest away from the Sun, and during its winter in the northern hemisphere, the nitrogen freezes out of the atmosphere.
The atmospheric pressure has tripled over the past three decades, but as the dwarf planet orbits, the modeling showed that most of the atmosphere would condense to the point that there is almost nothing left.
What the predictions show is that by 2030 the atmosphere is going to frost out and vanish around the entire planet. If it does freeze over, Pluto may appear brighter in the sky due to sunlight reflecting from it.
The findings will be published in the journal Astronomy & Astrophysics.
NASA’s New Horizons mission keeps revealing neat stuff about Pluto.
The latest: The dwarf planet has blue skies and small patches of water ice on its surface.
On Earth, blue skies are the result of the scattering of sunlight by gas molecules in the atmosphere. On Pluto, sunlight is scattered not by molecules but by a haze of soot-like particles called “tholins”, which are created as a result of chemical reactions involving methane and nitrogen high above Pluto.
Another difference is that while Earth’s sky looks blue to us most of the time, that doesn’t seem to be the case on Pluto. If you stood on Pluto and looked straight up, the sky would actually appear black.
Water ice was also detected in several places on Pluto’s surface, including impact craters and valleys. And if you’re envisioning patches of whitish-bluish stuff like the ice seen in chilly spots on Earth, think again. Pluto’s water ice is a crimson color, perhaps as a result of ice-covered tholins that fall to the surface.
The New Horizons spacecraft is now 3.1 billion miles (5 billion kilometers) from Earth and is still sending photos and data back to NASA. Stay tuned for more.