Pluto's frozen heart-shaped plain has been a mystery to astronomers since the picture-taking New Horizon flyby and a new study suggests it may not have been formed by a celestial collision as thought.
University of Maryland astronomy professor Douglas Hamilton and other researchers connected with the New Horizon spacecraft mission are examining what is called the plain's western Sputnik Planitia region, a deep basin containing frozen nitrogen, methane and carbon monoxide, according to NASA.
Their findings were published in the science journal Nature.
The heart-shaped area on the dwarf planet was one of the most talked about features when NASA's New Horizon spacecraft completed a flyby in 2015, sending back the first-ever detailed pictures of Pluto.
Sputnik Planitia sits opposite Pluto's large, tidally locked moon Charon, noted NASA.
Hamilton and his fellow researchers said in Nature that the western lobe could have been formed early in Pluto's life while the planet was quickly spinning.
"Once the ice cap forms, it provides a slight asymmetry that either locks toward or away from Charon when Pluto's spin slows to match the orbital motion of the moon," Hamilton said.
Hamilton said he created a model that showed how small ice deposits on the planet could have naturally attracted more ice by reflecting away solar light and heat.
In the process, temperatures remained low, attracting more ice and the cycle would repeat itself. Called the runaway albedo effect, this phenomenon would eventually lead to the single dominating ice cap that appears on Pluto.
Pluto's spin axis tilts 120 degrees, compared to Earth's 23.5-degree tilt, making the Sputnik Planitia one of the coldest spots on the dwarf planet, according to Hamilton's model.
"Modeling the dwarf planet's temperatures showed that when averaged over Pluto's 248-year orbit, the 30 degrees north and south latitudes emerged as the coldest places on the dwarf planet, far colder than either pole. Ice would have naturally formed around these latitudes, including at the center of Sputnik Planitia, which is located at 25 degrees north latitude."
According to another study presented in Nature last week, Spunik Planitia was formed long ago by the impact of a large Kuiper Belt object hitting Pluto,
"Sputnik Planitia is one of Pluto's crown jewels, and understanding its origin is a puzzle," said New Horizons principal investigator Alan Stern, of Colorado's Southwest Research Institute.
"These new papers take us a step closer to unraveling this mystery. Whatever caused Sputnik to form, nothing like it exists anywhere else in the solar system. Work to understand it will continue, but whatever that origin is, one thing is for certain – the exploration of Pluto has created new puzzles for 21st century planetary science," Stern continued.
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