Data obtained by NASA's New Horizons spacecraft shows that tiny, distant Pluto probably not only has an ocean under a frozen surface, but also, perhaps, kept lakes on its surface in the recent past. And it is likely that they will appear in the future.
Even on warm days for the planet, Pluto is too cold for surface lakes from water, but they may contain liquid nitrogen during those periods of time when the planet's atmosphere swells.
Pluto, which takes 248 years to rotate around the Sun, turns out to have large portions of areas with direct upper sunlight due to the extreme axial tilt of 120 degrees relative to the plane of its orbit. Earth, by comparison, has a slope of 23 degrees.
“This gives Pluto a much wider range of tropical latitudes than on Earth,” said New Horizon scientist Richard Binzel of the Massachusetts Institute of Technology.
Since the arctic and tropical zones alternatively stretch across such wide openings on the surface of a dwarf planet, Pluto has regions where both extremes occur, although not at the same time. Binzel noted that Pluto is also swinging, which leads to the fact that its axis rises an additional 20 degrees from its current orientation, causing long-term climatic cycles that far exceed anything that happens on Earth.
Pluto is now in an intermediate phase between its extreme climatic events, with a recent peak less than 1 million years ago. Temperatures today reach around -400 degrees Fahrenheit.
Changes in the amount of sunlight falling on Pluto have a direct impact on the atmosphere of Pluto. This was noted by the leading scientist of New Horizons Alan Stern from the South-West Research Institute.
“We believe that today Pluto’s atmospheric pressure is usually low and in the past it could be from 1,000 to 10,000 times higher,” said Stern, noting that it would have exceeded pressure on Mars 40 times.
Computer models show that when Pluto's temperature and atmospheric pressure are high, suitable conditions for liquid nitrogen are added. Additional evidence comes from the New Horizons apparatus. High-resolution images taken during the July 14 fly-around reveal features that look as if the areas were fluid. The images also show something resembling a frozen lake about 20 miles wide at its widest point, north of the Sputnik Planum plain, in the western smooth region of Pluto, similar in shape to the heart.
“Pluto is so dynamic that a variety of cases can be played in different epos,” said Stern. “We found this little planet where everything is connected to each other.”
The study was presented at the Lunar and Planetary Science Conference last week in Texas, and was submitted for publication in the journal Icarus.