Despite having average temperatures of roughly -400 degrees Fahrenheit, Pluto may have been home to lakes and rivers of liquid nitrogen within the last one-million years, and could be again one day, researchers from NASA’s New Horizons team revealed on Monday.
Speaking at the Lunar and Planetary Science Conference The Woodlands, Texas, New Horizons mission leader Alan Stern and his colleagues explained that data collected by the spacecraft as it flew past the dwarf planet last summer were used to create models detailing how its climate and atmospheric pressure have changed over the years.
Those models, National Geographic and New Scientist said, indicated that there were moments when the temperature and pressure would have been high enough for the frozen nitrogen ice on Pluto’s surface to melt and form lakes and rivers. The findings could help explain why the dwarf planet is home to terrain features that appear to have been cut by bodies of water.
Jim Green, director of NASA’s Planetary Science Division, told Nat Geo that the findings “did not surprise us… it shocked us,” while Stern added that the pressure on Pluto “changes radically.” At the moment, he explained, it is “atypically low,” and at its maximum, it can reach levels more than 20,000 times higher than the current levels.
This frozen lake was once liquid, studies suggest. (NASA/JHUAPL/SwRI)
It likely happened before, and it could happen again!
Based on those pressure variations during the course of the dwarf planet’s 248-year orbit, as well as recent observations collected by New Horizons, the researchers believe these pools could form again.
Since the dwarf planet’s axis is tilted by nearly 120 degrees, it undergoes extreme seasonal shifts as it makes its way around the sun, with some parts of the planet experiencing a half-century of constant sunlight while other regions endure decades of perpetual darkness, Nat Geo said. Over the course of millions of years, this can cause the atmosphere to thicken or become thinner.
These gullies appear to have been carved out by liquid nitrogen. (NASA/JHUAPL/SwRI)
This suggests that Pluto’s temperatures must also be fluctuating enough to cause nitrogen on the dwarf planet’s surface to change from a frozen solid into a gas, which also means that it is likely the conditions can allow liquid nitrogen to flow on Pluto’s surface. Of course, that hasn’t happened in nearly 800,000 years, which is when the study authors said was the last time Pluto’s orbit resulted in its warmest climate conditions.
During that time, the researchers explained, Pluto’s axis would have reached a tilt of about 103 degrees, causing its tropical region to extend near to the poles and the arctic to reach down to the dwarf planet’s equator, according to New Scientist. This would have driven atmospheric pressure levels to become higher than those found on Mars and 10 percent those that on Earth at sea level.
The pressure increase would have make it possible for liquid nitrogen to exist in lakes and rivers on the surface, the NASA team explained. Furthermore, the researchers believe that it could even happen again. While they are still in developing models of nitrogen-ice glacial flows spotted by New Horizons, the early indications are that the weight of the ice could cause the pressure to rise enough to once again allow a liquid layer to exist on the dwarf planet’s surface.
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Image credit: NASA/JPL
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