Pluto, the icy dwarf planet hanging out in the Kuiper Belt, may well have been hot when it formed and could have supported a subsurface liquid ocean early in its development.
According to a study published in Nature Geoscience, the origins of the no-longer-ninth-planet's chemical interactions between these oceans and the rocky materials below may have implications for ocean chemistry and the potential habitability of distant icy worlds.
The established accepted view is that Pluto was cold and icy when it formed in the distant Kuiper Belt, which extends from the orbit of Neptune. Although a liquid ocean is currently thought to flow under the thick icy shell, this was believed to have formed "much later" from the heat produced by radioactive elements in the little planet's rocky core.
Alan Stern, the NASA Science principal investigator of the New Horizons mission to explore Pluto and the Kuiper Belt, worked with Carver Bierson and Francis Nimmo of University of California Santa Cruz to create thermal model simulations of the evolution of the body's interior based on geological observations from the spacecraft.
The modelling of a cold beginning showed compressional stresses generated in the planet's icy shell that were not consistent with the structures observed on Pluto's surface by New Horizons when it passed by in 2015.
However, in a hot formation scenario, with an early subsurface ocean, the stresses generated in Pluto's shell fit with the extensional structures now seen on its surface. The researchers said that the "hot start" scenario may have been possible if Pluto formed quickly.
They went on to say that Pluto and other large dwarf planets in the Kuiper Belt may have been hot and had subsurface oceans at formation.
New Horizons data is causing a rethink of Pluto. Dunes of methane ice grains have been discovered there through examination of the data.
Pluto was discovered in 1930 by American Clyde Tombaugh and declared the ninth planet. It was, however, reclassified as a dwarf planet in 2006 when scientists began to find more and more similar-sized objects in the Kuiper Belt. Although Pluto didn't make the grade, data from New Horizons continues to show it remains worthy of investigation. ®