Pluto ceased to be a planet as such in 2006 and it seems that only in recent years, since the historic flyby of the New Horizons probe in 2015, have we been able to understand this dwarf planet in greater detail. We have learned a lot about this small world in our solar system, but a recent study has found evidence that in its early days it could have had a warm environment and a liquid ocean that froze over time.
Heat and ocean in the formation of Pluto
A new study, published in the journal Nature Geoscience , suggests that, contrary to previous analysis, Pluto may have had a “hot start” in the distant Kuiper belt, developing a subsurface liquid ocean much earlier than previously thought. A team of researchers from the University of California, Santa Cruz (USA) reached this conclusion by comparing different thermal simulations of the interior of Pluto with observations of the dwarf planet by NASA’s New Horizon spacecraft. Their numerical simulations and geological observations from New Horizons showed that Pluto was relatively hot when it formed and had a subsurface ocean.
“For a long time, there has been thought about the thermal evolution of Pluto and the ability of an ocean to survive to this day,” said Francis Nimmo, a planetary scientist in the Department of Earth and Planetary Sciences at the University of California Santa Cruz. “Now that we have images of Pluto’s surface from New Horizons, we can compare what we see with predictions from different models of thermal evolution.”
Since the New Horizons observations in 2015, the presumed subsurface salty ocean beneath Pluto’s icy shell has been a particularly intriguing feature. Researchers have traditionally attributed the formation of Pluto’s ocean to the heat generated by radioactive decay inside the dwarf planet, carved out of the frozen ball of ice and rock. However, this cold start scenario would not explain some of Pluto’s surface features seen by New Horizons. A hot formation, yes.
Because water expands when it freezes and contracts when it melts, the hot and cold start-up scenarios have different implications for the tectonics and resulting surface characteristics of Pluto , explained Carver Bierson, also of UCSC.
“If it started to cool and the ice melted internally, Pluto would have contracted and we should see compression characteristics on its surface, whereas if it started to warm it should have expanded as the ocean froze and we should see extension characteristics on the surface. surface, “Bierson continued. “We see a lot of evidence for expansion, but we don’t see evidence of compression, so the observations are more consistent with Pluto starting with a liquid ocean.”
For Pluto to be warm enough to have a liquid ocean in its early days, a large amount of gravitational energy must have been retained as heat. For that to happen, his training also had to be swift.
“How Pluto formed is very important for its thermal evolution. If it accumulates very slowly, the hot material on the surface radiates energy into space, but if it accumulates fast enough, the heat is trapped inside,” the authors clarify.
From their calculations, the team shows a new model of dwarf planet formation: one formed in several stages within a period of less than 30,000 years; time the team calculated it would take for the hot start model. And, the researchers note, their results imply that other large Kuiper Belt objects could also have formed fast and hot and had liquid oceans.
Referencia: Evidence for a hot start and early ocean formation on Pluto, Nature Geoscience (2020). DOI: 10.1038/s41561-020-0595-0 , www.nature.com/articles/s41561-020-0595-0
