Arthur J. Villasanta – Fourth Estate Contributor
San Antonio, TX, United States (4E) – Scientists can’t seem to make-up their minds as to what kind of an object Pluto really is. Pluto was classified as a planet form the time of its discovery in 1930 up until 2006 when the International Astronomical Union (IAU) demoted it to the status of a dwarf planet in the Kuiper Belt (the ring of asteroids and rocks beyond Neptune).
Now, however, a team of scientists at the Southwest Research Institute (SWRI) in San Antonio, Texas believe Pluto is really a comet — and a massive one at that – consisting of more than a billion smaller comets squished together.
The Southwest team has developed a new hypothesis about how Pluto formed at the edge of our solar system. This theory is called the “cosmochemical model of Pluto formation.” This model was triggered by findings about a large glacier named Sputnik Planitia, which consists of nitrogen-packed ice. Sputnik Planitia is located at the left lobe of the Pluto’s heart-shaped Tombaugh Regio area.
“We’ve developed what we call ‘the giant comet’ cosmochemical model of Pluto formation,” said Dr. Christopher Glein of SWRI’s Space Science and Engineering Division and lead author of the study. “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.”
Comets form by agglomeration, which suggests Pluto might be a comet, after all. Scientists previously thought Pluto formed like a planet 4.6 billion years ago, after gas and ice bound together with a rocky core to create an enormous sphere in the Sun’s protoplanetary disc.
Now, however, unprecedented observations carried out by spacecraft like New Horizons and Rosetta have given scientists a clearer understanding of how Pluto really came to be. SWRI scientists suggest Pluto might have been formed by one billion comets that came together because they find it odd that Pluto and Comet 67P/Churyumov-Gerasimenko — the one where ESA landed a probe in 2014 — share so much of their chemical makeup. For instance, Pluto’s nitrogen-rich Sputnik Planitia is unnaturally similar to Comet 67P.
The solar system’s planets formed by accretion of material from enormous discs that orbited the early Sun. The matter inside the rapidly spinning disk around the parent star merged to form clumps, steadily accumulating until these turn into asteroids, comets, planets and moons.
Pluto was always thought to have formed much in the same way. Dr. Glein and colleagues at SwRI’s Space Science and Engineering Division, begged to differ, however,
There’s also too much nitrogen on Pluto. Earth’s atmosphere consists of 78% nitrogen, but Pluto’s, which is far colder, is 98% nitrogen. That’s an unusual proportion of nitrogen, both at the surface and in the atmosphere, which isn’t easily explained by the conventional planetary formation theory. Instead, it points to more than a billion comets merging to form the icy object called Pluto..
“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,” said Dr. Glein.
“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.”
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