Pluto may not be considered a planet anymore, but astronomers are still trying to figure out how the dwarf planet came into existence in the outer reaches of our solar system.
A new theory exploring the planet’s formation proposes a bizarre explanation for how Pluto was born. According to researchers at the Southwest Research Institute (SwRI) in San Antonio, Texas, the dwarf planet may have been formed from a billion comets, clustering together in the Kuiper Belt.
This would explain why Pluto is so different from the eight official planets of the solar system, and why it has so much nitrogen and so little carbon monoxide. The new theory is detailed in paper available on the arXiv server and is due to be published in the journal Icarus.
“We’ve developed what we call ‘the giant comet’ cosmochemical model of Pluto formation,” study lead author Dr. Christopher Glein, from the institute’s Space Science and Engineering Division, said in a SwRI news release.
The research is based on data from two separate missions, NASA’s New Horizons and the Rosetta mission run by the European Space Agency. While the New Horizons spacecraft performed a flyby of Pluto in July 2015, Rosetta orbited Comet 67P/Churyumov-Gerasimenko from 2014 through 2016 and even deployed its Philae lander on the comet’s icy surface. The two missions combined have offered a bounty of data both on the make up of Pluto and on comets.
The new study analyzed Pluto’s chemical composition and uncovered a number of similarities between the dwarf planet and comet 67P, the famous “snowstorm” comet made popular on Twitter last month.
“We found an intriguing consistency between the estimated amount of nitrogen inside the glacier and the amount that would be expected if Pluto was formed by the agglomeration of roughly a billion comets or other Kuiper Belt objects similar in chemical composition to 67P, the comet explored by Rosetta,” Glein explained.
Study authors compared their proposed comet model with an alternative explanation for Pluto’s formation, namely a solar model in which the dwarf planet may have been created through the accretion of very cold ices with chemical compositions similar to that of the sun.
The study examined both models in an effort to understand why Pluto’s Sputnik Planitia, a large glacier that constitutes the left lobe of the dwarf planet’s iconic “heart” feature, contains so much nitrogen-rich ice.
The authors also wanted to find out how much nitrogen may have leaked out into space over time from Pluto’s atmosphere, which according to Science Alert is made up of 98 percent nitrogen.
A big challenge was posed by the low levels of carbon monoxide in the dwarf planet’s atmosphere. But the researchers’ explanation for the missing carbon dioxide is that it was either destroyed by liquid water or it’s potentially trapped under Pluto’s surface.
“Our research suggests that Pluto’s initial chemical makeup, inherited from cometary building blocks, was chemically modified by liquid water, perhaps even in a subsurface ocean,” Glein pointed out.
Since the comet model ultimately offered more explanations for Pluto’s unusual composition, the authors deemed it more plausible than the solar model, Science Alert reports.
Glein hopes that his study will help astronomers learn more about Pluto’s origin and evolution.
“Using chemistry as a detective’s tool, we are able to trace certain features we see on Pluto today to formation processes from long ago. This leads to a new appreciation of the richness of Pluto’s ‘life story,’ which we are only starting to grasp.”