The ice of Pluto is a two-lobed formation on its surface which has sparked the interest of researchers ever since NASA's New Horizons discovered it back in 2015. One of the two lobes, the western one, has been subjected to more scientific attention due to its mysterious formation and the types of ice it hosts.
The lobe was named Sputnik Planitia informally, and it is a deep basin containing carbon monoxide, methane and frozen nitrogen. The lobe appears to be opposite to the dwarf planet's tidally locked moon and various scenarios have been formulated in regard to its formation.
Pluto's Ice Formation
What all of the theories have in common is the idea that the formation is an impact basin, which was created while a smaller body stroke Pluto with extraordinarily high speed. A new research conducted at the University of Maryland, however, suggests that the ice was formed early in Pluto's history, which would place its attributes as evolutionary consequences.
The research was published, Dec. 1, in the journal Nature, suggesting that the ice cap formed early, and not due to an impact.
The researcher used a model that he developed himself and explained that the original location of Sputnik Planitia may have been due to the dwarf planet's bizarre climate. Another contributing factor could be the spin axis tilted by 120 degrees, which is rather unusual, especially when compared to Earth's axis, whose inclination only reaches 23.5 degrees.
Pluto's Early Formation And Charon
The researcher analyzed the temperatures, discovering that the 30 degrees north and south latitudes were the coldest places on Pluto, when averaged over its 248-year orbit. According to this study, these spots were way colder than the poles, which could mean that ice formed as part of a natural process around these latitudes.
This discovery places the icy center of Sputnik Planitia, located at 25 degree north altitude, as a natural formation instead of a occurrence due to an impact with an external object.
This new theory proposing weather instead of impact as a cause of lobe formation places the shift of Pluto's center of mass at around the same time that Charon's gravitational force slowed the dwarf planet's rotation. When this happened, Pluto had equal chances of facing Charon or as far away from it as possible, as a result of several million years of progressively becoming tidally locked.
The new paper does not require the existence of an ocean on Pluto, but it never argued against such a possibility, either.
"There is an ocean-free path to explaining the key features of Sputnik Planitia. But while Pluto need not have an interior ocean, conversely, nothing in my study argues against such an ocean," noted Douglas Hamilton, professor of astronomy and lead author of the paper, in an email to Seeker.